Free B500B and B500C reinforcement bar calculator for rebar weight, kg/m, total tonnes, steel area and estimated UK supply cost.
Use this High Yield Bar Calculator UK to estimate the weight of reinforcement bars used in beams, slabs, columns, foundations, retaining walls, concrete pads and general RC work. Select the bar diameter, grade, length, number of bars, lap or cutting allowance and estimated steel price to calculate kg per metre, total linear metres, total weight, tonnes, steel area and supply cost.
```A high yield bar calculator is used to estimate the quantity of reinforcement steel required for reinforced concrete work. In the UK, high yield reinforcement normally refers to ribbed steel bars used inside concrete beams, slabs, columns, foundations, retaining walls and other structural concrete elements. The ribs improve bond with concrete, while the high yield strength allows the bar to resist tensile forces after the concrete cracks in tension.
```This High Yield Bar Calculator UK helps builders, quantity surveyors, estimators, engineers, students and self-builders convert bar diameter, length and quantity into total weight and cost. It is useful for early budgeting, reinforcement schedules, material ordering and checking whether a supplier quote looks reasonable. Enter the bar diameter, the length of each bar, the number of bars and an allowance for laps, hooks, trimming or wastage. The calculator then estimates kg per metre, total linear metres, total kilograms, tonnes, steel area and a practical cost allowance.
The calculator is not a structural design tool. It does not decide how much reinforcement a beam or slab requires. That decision depends on span, loading, concrete grade, cover, exposure class, fire resistance, crack control and Eurocode design checks. What this tool does is turn a known reinforcement requirement into a clear material quantity. If your engineer has specified 20 bars of T12 at 6m long, or 40 bars of T16 with laps, this calculator helps you work out the tonnage and budget before placing an order.
B500B is widely used for UK ribbed reinforcement, with 500 N/mm² characteristic yield strength.
Rebar kg/m can be estimated from diameter using the standard formula d² ÷ 162.
Convert bar marks, lengths and quantities into total metres, kg and tonnes before ordering.
Add cutting, bending, delivery and wastage allowances to create a more realistic reinforcement budget.
Start by selecting the reinforcement grade. For most modern UK reinforced concrete work, B500B high yield ribbed bar is a common choice. B500C may be specified where higher ductility is required. Older drawings may mention 460 N/mm² high yield bars, especially on legacy projects. Mild steel round bars are normally different from modern high yield ribbed reinforcement and should not be substituted without design approval.
```Next, select the bar diameter. UK drawings often label reinforcement as T10, T12, T16 or T20. The number indicates the nominal diameter in millimetres. A T12 bar is a 12mm ribbed bar. A T16 bar is a 16mm ribbed bar. Larger diameters are heavier and provide more steel area, but they are harder to bend and need more cover, spacing and detailing consideration.
Enter the length per bar in metres. This may be the stock length, a cut length from the bar schedule or the approximate length measured from site drawings. Then enter the number of bars. If you are calculating multiple bar marks, you can either calculate each bar mark separately or combine bars with the same diameter and similar length. For a proper bar bending schedule, keep each diameter and shape code separate so the order remains clear.
The lap, hook or cutting allowance field is used where the exact schedule length is not yet final. Reinforcement often needs lap lengths, anchorage bends, crank lengths, hooks, site trimming or extra length around corners. The wastage allowance is separate and covers offcuts, mistakes, damage, schedule changes or small site losses. A 5% wastage allowance is common for basic budgeting, but complicated cut-and-bent work may need a different allowance.
The price per tonne field allows you to estimate the supply cost. Steel prices move with the market, order size, delivery distance and whether you need straight bars, cut-and-bent bars, prefabricated cages or a certified supplier. The cutting, bending and delivery percentage is an additional budgeting allowance. For straight loose bars collected locally, this may be low. For cut-and-bent reinforcement delivered to site, the uplift can be much higher.
```The standard quick formula for reinforcement bar weight is:
Weight per metre in kg/m = bar diameter² ÷ 162
```For example, a 12mm high yield bar weighs approximately 12 × 12 ÷ 162 = 0.888 kg per metre. A 16mm bar weighs approximately 16 × 16 ÷ 162 = 1.58 kg per metre. A 20mm bar weighs approximately 20 × 20 ÷ 162 = 2.47 kg per metre. The formula is based on the density of steel and the circular cross-sectional area of the bar.
The calculator uses this formula because it is simple, widely recognised and accurate enough for estimating reinforcement quantities. Supplier tables may show tiny rounding differences, but for normal material take-offs the formula gives a reliable result. For final procurement, always follow the bar bending schedule, supplier measured lengths and certified product data.
| Bar Size | Diameter | Area per Bar | Approx. Weight | Typical Domestic / Construction Use |
|---|---|---|---|---|
| T6 / H6 | 6mm | 28.3 mm² | 0.222 kg/m | Light links, small ties, light reinforcement where specified. |
| T8 / H8 | 8mm | 50.3 mm² | 0.395 kg/m | Links, stirrups, light slabs, small concrete details. |
| T10 / H10 | 10mm | 78.5 mm² | 0.617 kg/m | Small slabs, starter bars, light mesh alternatives, links. |
| T12 / H12 | 12mm | 113.1 mm² | 0.888 kg/m | Ground beams, slabs, foundations, lintel cages, walls. |
| T16 / H16 | 16mm | 201.1 mm² | 1.58 kg/m | Beams, retaining walls, columns, raft slabs, heavier foundations. |
| T20 / H20 | 20mm | 314.2 mm² | 2.47 kg/m | Larger beams, heavy foundations, transfer elements, columns. |
| T25 / H25 | 25mm | 490.9 mm² | 3.86 kg/m | Heavy structural concrete, civil engineering and large frames. |
| T32 / H32 | 32mm | 804.2 mm² | 6.32 kg/m | Major structural work, piles, deep beams and heavily loaded elements. |
| T40 / H40 | 40mm | 1256.6 mm² | 9.88 kg/m | Specialist heavy civil engineering and major reinforced concrete works. |
High yield reinforcement bar is steel reinforcement with a higher yield strength than traditional mild steel. In reinforced concrete, concrete is strong in compression but weak in tension. Steel bars are placed where tensile forces are expected so the concrete and steel work together. The concrete protects the steel and provides compressive strength, while the steel carries tensile forces and controls cracking.
```Modern high yield bars used in the UK are usually ribbed rather than smooth. The ribs improve mechanical bond between the bar and the surrounding concrete. Good bond is essential because the forces must transfer between concrete and steel along the length of the bar. Smooth mild steel bars may still appear in some older details or specialist uses, but they are not the same as modern ribbed high yield reinforcement.
The common notation B500B can be understood in simple terms. The “B” indicates reinforcing steel, “500” indicates a characteristic yield strength of 500 N/mm², and the final letter describes the ductility class. Ductility is important because reinforcement should not fail in a brittle way. Higher ductility allows greater deformation before failure, which can be important in structural safety, redistribution and detailing.
For quantity estimating, the main things you need are diameter, length, quantity and weight per metre. For design, many more checks are required. A structural engineer must consider bending, shear, anchorage, lap lengths, crack widths, cover, fire, durability, deflection and constructability. This calculator focuses on quantity and cost, not design approval.
```B500B is the grade most people associate with modern UK high yield reinforcement. It provides 500 N/mm² characteristic yield strength and a ductility class suitable for many reinforced concrete projects. B500C has the same characteristic yield strength but a higher ductility class. It may be specified for projects where greater ductility is important, although it is not always required for ordinary domestic work.
```Older drawings may refer to high yield bars with 460 N/mm² strength. If you are working from older structural drawings, do not simply change the grade without checking the design basis. In many situations, a stronger modern bar may appear beneficial, but design detailing, ductility, bond, lap lengths and code assumptions still matter. When modifying existing structures, always seek professional design advice.
The calculator includes 500 N/mm², 460 N/mm² and 250 N/mm² options mainly for identification and reporting. The weight of a steel bar depends on its diameter and length, not its yield strength. A 12mm B500B bar and a 12mm B500C bar have essentially the same nominal weight per metre. The grade affects design resistance and ductility, not the basic kg/m take-off.
Even though grade does not change the weight calculation, it matters for ordering and compliance. The reinforcement delivered to site should match the drawings and specification. Delivery notes, certification, bar markings and CARES approval may be required on professional projects. Substituting a different grade, diameter or ductility class can create design and compliance problems.
If your drawing says B500B T16 bars, order B500B T16 bars unless the engineer approves an alternative. If the supplier offers a substitute, get confirmation before placing the order. For small DIY work, this may sound excessive, but for structural concrete it is essential.
```Reinforcement take-off is the process of turning design drawings into measurable quantities. A drawing may show bar marks, diameters, spacing, shape codes, lap locations and cover requirements. The estimator must convert those notes into bar lengths and quantities. This calculator supports that process by giving a quick weight and cost for each set of bars.
```In beams, high yield bars are commonly used as main tension reinforcement, compression reinforcement and shear links. Main bars usually run along the beam length. Links or stirrups wrap around the main bars and resist shear while holding the cage together. When estimating beam reinforcement, count the number of top bars, bottom bars, additional bars over supports, links and any starter or continuity bars. Each bar mark should be calculated separately for accuracy.
Slabs often use bars at regular centres in one or two directions, or they may use mesh reinforcement. For loose bar slabs, calculate the number of bars by dividing the slab width by spacing and adding one bar at the edge where appropriate. Then multiply by bar length, including cover, laps and trimming. Slab reinforcement often needs a distribution of bars rather than a small number of individual bars, so a separate area-per-metre check may also be useful.
Columns use vertical bars and links. The vertical bars carry compression and bending forces, while links restrain the bars and help confinement. Bar lengths may include starter bars, laps to the next lift, hooks or anchorage details. Because columns are structural elements with critical detailing, do not estimate them by eye. Use the engineer’s bar schedule and calculate each diameter carefully.
Foundations, strip footings, pad bases and ground beams commonly use T12, T16 or larger bars depending on design. In domestic projects, foundation cages can contain top and bottom bars plus links. For retaining walls and rafts, reinforcement may be more complex, with starter bars, vertical bars, horizontal bars and kicker details. Add allowances for laps and offcuts, but do not remove bars or reduce diameters without design approval.
```Many reinforcement calculations go wrong because the user measures only the clear length and forgets laps, bends, hooks and anchorage. A bar in a real concrete element rarely stops exactly at the visible dimension. It may need to extend into supports, lap with another bar, bend around a corner, hook into a wall or continue through a construction joint. These extra lengths can add a significant quantity of steel across a full project.
```Lap length is the length over which two bars overlap so forces can transfer between them. The correct lap length depends on bar diameter, concrete strength, bond conditions, cover, confinement and design code rules. Do not use a fixed lap rule for structural design unless your engineer has specified it. For early estimating, an allowance can be used, but final schedules should follow the structural drawings.
Hooks and bends also add length. A U-bar, L-bar, link or starter bar may look short in plan, but the developed length around bends can increase the actual cut length. Proper bar bending schedules use shape codes to define this. If the supplier is providing cut-and-bent reinforcement, they will use the schedule to fabricate each bar mark. If you are buying straight bars for site cutting, make sure the stock length allows enough material for bends and laps.
The calculator includes two allowance fields. The lap, hook or cutting allowance increases the total linear length before the weight is calculated. The wastage allowance then adds extra weight for offcuts and site losses. Keeping these allowances separate gives a more realistic estimate than using one vague percentage.
```The cost of high yield reinforcement in the UK varies with steel price, supplier, order quantity, bar diameter, fabrication requirement, certification, delivery distance and whether you buy loose straight bars or cut-and-bent reinforcement. Small online or merchant orders can be much more expensive per tonne than large commercial orders. A few lengths of T12 bought locally may have a high unit price, while a multi-tonne cut-and-bent order for a contractor may be priced differently.
```The calculator uses a price per tonne because reinforcement is often quoted by weight. If your supplier quotes per length, you can still use the calculator to convert the order into weight and compare prices. For example, if a 6m T12 bar weighs about 5.33kg and the supplier price is known, you can check the effective price per tonne. This is useful for comparing merchants, online suppliers and reinforcement fabricators.
| Cost Item | What It Includes | Why It Matters |
|---|---|---|
| Steel supply | Basic weight of reinforcement bars | Main cost driver for loose straight bars and large orders. |
| Cutting and bending | Fabrication to bar bending schedule | Essential for complex cages, links, starter bars and shaped reinforcement. |
| Delivery | Transport to site or collection yard | Can be significant for long bars, heavy bundles or small orders. |
| Certification | Traceability, CARES approval and compliance documents | Often required for professional structural concrete projects. |
| Wastage | Offcuts, changes, damage and site losses | Prevents under-ordering and helps avoid delays. |
For budgeting, enter your local supply price and a realistic uplift for cutting, bending and delivery. For final orders, use supplier quotes and a proper bar bending schedule. If reinforcement is part of a building control or engineered structure, keep records of grade, certification and delivery documentation.
```Bar weight and steel area increase with the square of diameter. This means a 20mm bar is not simply twice as heavy as a 10mm bar. It is about four times the area and weight per metre. This is why changing bar diameter has a big effect on both structural capacity and cost. A small diameter change across hundreds of metres can add or remove a large amount of steel.
```For estimating, this square relationship is important. If a project changes from T12 to T16 bars, the number of bars may reduce, but the total weight may still increase. If a slab uses bars at closer spacing, total length increases. If a beam changes from two T16 bars to three T20 bars, the weight and cost can rise sharply. Use the calculator to test scenarios, but only an engineer should approve structural substitutions.
The area per bar is calculated using the circular area formula. A T12 bar has about 113mm² of steel area, while a T16 bar has about 201mm². A T20 bar has about 314mm². In design calculations, steel area is used to check bending resistance, crack control and minimum reinforcement. In quantity surveying, weight is more important because suppliers quote by length, bar mark or tonne.
Design note: Do not replace several smaller bars with one larger bar without checking spacing, bond, crack control, anchorage and cover. Equal steel area does not always mean equal structural behaviour or buildability.
Loose high yield bars and reinforcement mesh are both used to reinforce concrete, but they are ordered and installed differently. Loose bars are flexible for beams, columns, foundations, retaining walls and custom reinforcement cages. Mesh sheets are often quicker for slabs, driveways, paths and lightly reinforced concrete areas where a regular grid is required.
```Mesh is normally sold by sheet size and mesh type, such as A142, A193, A252 or A393. The mesh reference relates to steel area per metre. Loose bars are specified by diameter and spacing or by bar mark. A drawing may show T12 bars at 200mm centres, which is a loose-bar instruction. Another drawing may show A393 mesh, which is a sheet mesh instruction.
Do not switch between mesh and loose bars without checking the design. Mesh has welded intersections and defined spacing. Loose bars require correct tying, cover and support chairs. For small concrete pads, mesh may be easier. For beams and structural details, loose high yield bars are often required. This calculator is mainly for loose high yield bar take-off, but it can also help compare the weight of loose bars against mesh-based alternatives.
```Before ordering reinforcement, collect the key information from your drawings or engineer: bar diameter, grade, bar mark, shape code, cut length, quantity, cover requirements and any notes about laps or couplers. If the project has a bar bending schedule, use it. If the drawing only gives outline reinforcement, ask for clarification before ordering large quantities.
```For small projects, local builder’s merchants may stock common sizes such as T10, T12 and T16 in standard lengths. For larger projects, reinforcement fabricators can supply cut-and-bent bars, links, cages and scheduled bundles. Cut-and-bent reinforcement saves site labour and reduces mistakes, but it requires accurate schedules and lead time.
When the order arrives, check the delivery against the schedule. Confirm diameter, length, quantity, bundle tags and certification. Store bars off the ground where practical and avoid heavy contamination with mud, oil or loose rust. Light surface rust is common on reinforcement and usually not a problem, but heavy scaling, pitting or contamination should be checked before use.
On site, reinforcement should be fixed with correct cover spacers and chairs. Bars should not sit directly on the ground or shuttering where cover is required. Poor cover can reduce durability and fire performance. Good ordering is only the first step; correct placement is equally important.
```The first common mistake is calculating only the visible length and forgetting laps. If a foundation has several bars that overlap, the lap lengths can add many metres of steel across the project. The second mistake is using the wrong diameter. T12 and T16 may look similar to an untrained eye, but the weight and steel area are very different. Always check the drawing and use calipers or supplier labels if unsure.
```The third mistake is mixing up metres and millimetres. Bar lengths on schedules may be shown in millimetres, such as 6000mm, while calculators usually use metres, such as 6m. Entering 6000 as metres would create an absurd result. This calculator expects length per bar in metres.
The fourth mistake is assuming grade changes weight. B500B and B500C have the same nominal bar weight for the same diameter. Grade affects yield strength and ductility, not kg/m. The fifth mistake is forgetting delivery and fabrication cost. A reinforcement order is not always just steel weight multiplied by commodity price. Cutting, bending, certification, delivery, small-order charges and VAT can change the final invoice.
The final mistake is using a quantity calculator as if it were a design calculator. A quantity calculator can tell you how heavy the bars are. It cannot tell you whether those bars are structurally sufficient. For any load-bearing concrete element, follow the structural engineer’s design.
```Use the formula diameter squared divided by 162 to estimate weight in kg per metre. For example, a 12mm bar is 12 × 12 ÷ 162, which equals about 0.888 kg/m. Multiply kg/m by total length to calculate total reinforcement weight.
B500B is a common UK high yield ribbed reinforcement bar grade. The 500 refers to 500 N/mm² characteristic yield strength, while the final B refers to the ductility class. It is widely used in reinforced concrete beams, slabs, foundations, walls and columns.
B500B and B500C have the same nominal characteristic yield strength of 500 N/mm², but B500C has a higher ductility class. The correct grade should match the structural drawing or engineer’s specification.
No. For the same diameter and length, B500B and B500C have the same nominal weight. Weight depends on bar diameter and length, not ductility class. Grade matters for design and compliance, but not the basic kg/m calculation.
A 12mm high yield bar weighs approximately 0.888 kg per metre. A 6m length weighs about 5.33 kg before any cutting, lap or wastage allowance.
A 16mm high yield reinforcement bar weighs approximately 1.58 kg per metre. A 6m length weighs about 9.48 kg before allowances.
A 20mm high yield bar weighs approximately 2.47 kg per metre. It is much heavier than T12 or T16 because bar weight increases with diameter squared.
T12 usually means a 12mm high yield deformed reinforcement bar. The number indicates nominal diameter in millimetres. Similar notation is used for T10, T16, T20 and other common UK bar sizes.
H12 is another way of referring to a 12mm high yield reinforcement bar. Some drawings and suppliers use H notation, while others use T notation. Always confirm the project specification and bar schedule.
A 12mm bar weighs about 0.888 kg/m. One tonne is 1000 kg, so one tonne contains about 1126 linear metres of 12mm bar. If bars are 6m long, that is roughly 187 full 6m lengths before allowances.
A 16mm bar weighs about 1.58 kg/m. One tonne contains about 633 linear metres of 16mm bar. If bars are 6m long, that is roughly 105 full 6m lengths before laps, cuts or wastage.
For basic budgeting, 3% to 5% wastage may be used for simple straight bars. More complex cut-and-bent reinforcement, site changes, many bar marks or awkward shapes may require a higher allowance. Final orders should follow the bar bending schedule.
Yes, if the entered bar length does not already include laps. Lap lengths can add a significant quantity of steel, especially in slabs, walls and long beams. If your bar bending schedule already includes the full cut length, avoid adding the same lap allowance twice.
No. This calculator estimates reinforcement weight and cost only. It does not design the reinforcement, check bending resistance, shear, deflection, crack width, anchorage, cover or fire requirements. Structural concrete should be designed by a competent professional.
Do not substitute reinforcement without design approval. Larger bars may provide more area, but they also affect spacing, crack control, bond, cover, anchorage and constructability. Always follow the engineer’s drawings.
Foundation reinforcement depends on the design. Domestic foundations often use T12 or T16 bars, but larger or smaller sizes may be specified depending on load, ground condition, foundation type and structural layout.
Concrete slabs may use mesh or loose bars such as T10, T12 or T16 depending on span, loading, slab thickness and design. Light domestic slabs may use mesh, while structural slabs need engineered reinforcement details.
For professional structural concrete work, reinforcement should normally match the specified standard and certification requirements. Delivery notes, traceability and approved supplier documentation may be required for building control, engineers or quality records.