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Rebar Weight Calculator

How to Calculate Rebar Weight: Bar kg/m, Mesh Sheets and Order Quantities

Reinforcement is ordered by weight but scheduled by length. Learn the d²/162 rule for bar weight, how to weigh mesh sheets like A393, how much wastage to add and how to estimate cost, with worked examples and a free calculator.

Last updated 7 November 2026

Why weight matters

Reinforcement is drawn and scheduled by bar size and length, but it is bought, delivered and handled by weight. You need the weight to place an order, check a delivery ticket, plan lifting and handling, and price the job. A quick, reliable way to convert lengths to kilograms saves time at the desk and on site.

KaelSite’s free Rebar Weight Calculator handles both reinforcing bars and mesh sheets, with wastage and cost.

The d²/162 rule for bars

For steel reinforcing bar, the weight per metre is approximately:

weight (kg/m) = d² ÷ 162

where d is the nominal bar diameter in millimetres. Multiply by the total length in metres for kilograms, and divide by 1,000 for tonnes.

Bar Weight per metre
6 mm 0.222 kg/m
8 mm 0.395 kg/m
10 mm 0.617 kg/m
12 mm 0.889 kg/m
16 mm 1.580 kg/m
20 mm 2.469 kg/m
25 mm 3.858 kg/m
32 mm 6.321 kg/m

 

In UK practice, H12 means a high-yield deformed bar with a 12 mm nominal diameter, H16 is 16 mm, and so on. The calculator covers diameters from 6 to 32 mm.

Weighing mesh

Welded mesh, also called fabric, is sold in sheets and weighed per square metre. For example, A393 has a nominal mass of about 6.16 kg/m². A standard 4.8 × 2.4 m sheet is roughly 11.5 m², so each sheet weighs about 71 kg before laps and wastage. Other fabrics such as A142, A193, A252, B and C meshes have different kg/m² figures, so pick the right type or enter a custom mass.

Worked examples

1. Strip foundation bars
Six H12 bars, each 12 m long:
Total length = 6 × 12 = 72 m
Weight = 72 × 0.889 = 64.0 kg
With 10% for laps and cutting: 64.0 × 1.10 = 70.4 kg

2. Column cage bars
Twenty-four H20 bars, each 6 m long:
Total length = 24 × 6 = 144 m
Weight = 144 × 2.469 = 355.6 kg
With 5% wastage: 355.6 × 1.05 = 373 kg (0.373 tonnes)
As an example only, at £850 per tonne the steel would cost about £317. Use your supplier’s price.

3. A393 mesh in a slab
A slab 6 m × 4 m is 24 m² of mesh.
Net weight = 24 × 6.16 = 147.8 kg
One sheet is about 11.5 m², so you need at least 3 whole sheets (3 × 71 = about 213 kg) before laps. Because sheets are bought whole and overlap at laps, the weight you order is higher than the net figure.

Wastage and laps

Add an allowance for cutting waste, laps, chairs and offcuts. A few percent is typical, and complex shapes need more. Enter your own percentage so the order weight matches what you will really buy. For bars, a cutting plan also helps reduce waste: try our Material Cutting Optimiser for fitting required lengths to standard 12 m bars.

Estimating cost

Cost = order weight × price. Enter a price per tonne or per kilogram. The figure is an estimate and excludes fabrication, delivery, couplers and VAT unless they are already in your rate.

Common mistakes

  • Using the wrong diameter. A 16 mm bar weighs more than twice a 10 mm bar, so check the schedule.
  • Mixing metres and millimetres. A bar length of 6,000 entered as metres gives a result 1,000 times too large.
  • Forgetting laps and wastage. The net weight is not what you order.
  • Ignoring whole sheets for mesh. You buy complete sheets, so round up and allow for overlaps.
  • Treating d²/162 as exact. It is a standard approximation, so use supplier data when you need certified weights.
  • Leaving out cover and spacers. These do not add to bar weight but must be on the order.

UK standards and checks

Reinforcing steel in the UK is typically supplied to BS 4449, with steel fabric to BS 4483. Bar bending schedules follow BS 8666, which covers how steel reinforcement is scheduled, dimensioned, bent and cut. Check that your steel comes from a certified supplier, for example one holding CARES approval, and match deliveries against the schedule. Lap lengths, cover and bar arrangement come from the design, not from the weight calculation.

Frequently asked questions

How do you calculate rebar weight?
Use weight per metre ≈ d² ÷ 162 with d in millimetres, multiply by the total length for kilograms and divide by 1,000 for tonnes.

What does H12 or H16 mean?
H means high-yield deformed bar, and the number is the nominal diameter in millimetres.

How much does A393 mesh weigh?
About 6.16 kg/m², so roughly 71 kg for a standard 4.8 × 2.4 m sheet.

Should I add wastage for reinforcement?
Yes for ordering. Cutting, laps and offcuts typically add a few percent.

How do I estimate rebar cost?
Multiply order weight by the price per tonne or per kilogram.

Can I calculate mesh and bars in one place?
Yes. The calculator has a mode for bars and a mode for mesh, using the same wastage and cost fields.

Related calculators

Reinforcement is one part of a concrete job. These tools cover the rest:

See all of them in our complete guide to free construction calculators.

Keep your reinforcement records in one place

Steel inspections, delivery tickets and photos before the pour all need recording. KaelSite helps UK site teams manage inspections, safety and reporting from one mobile-first app. Explore KaelSite features.

References