TMT Steel Weight Calculator
Home & ConstructionConvert a bar schedule to kilograms and tonnes using the d²/162 rule, across every TMT size.
Runs entirely in your browser — nothing is uploaded
Steel is drawn by length and bought by weight, and converting between the two is the whole job. The site formula is d²/162 kilograms per metre — not a rule of thumb but the exact expression rounded — and this works it across as many bar groups as your schedule has, adds an offcut allowance, and cross-checks the total against the concrete it sits in.
What people do next
Features
- Any number of bar groups, given as pieces × length or as a total length.
- Every rolled TMT size from 6 mm to 40 mm.
- Weight per metre and per 12 m bar, shown for each group.
- Cross-check against typical steel per cubic metre of concrete, by member.
- Wastage allowance for offcuts, and cost at your rate per kg.
- Runs entirely in your browser — nothing is uploaded.
How to use the TMT Steel Weight Calculator
- 1Add a bar group for each diameter in your schedule.
- 2Give it either a piece count and length, or a total length.
- 3Set the wastage allowance and your rate per kilogram.
- 4Read the total weight, the number of 12 m bars to order, and the cost.
Frequently asked questions
What is the d²/162 formula and where does it come from?
It gives the weight of one metre of round bar in kilograms, where d is the diameter in millimetres. It is not an approximation invented for site use — it is the exact expression rounded. A bar of diameter d has a cross-section of π·d²/4 mm², and steel weighs 7,850 kg/m³, so the weight per metre is d² × 7850 × π ÷ 4 ÷ 1,000,000, which is d² ÷ 162.28. Using 162 is the convention and is within a quarter of a percent.
What does a 12 mm TMT bar weigh?
0.889 kg per metre, so a standard 12 m bar is about 10.67 kg. For the other common sizes: 8 mm is 0.395 kg/m, 10 mm is 0.617, 16 mm is 1.580, 20 mm is 2.469 and 25 mm is 3.858. Those are the figures on every steel merchant's chart, and they all come from the same formula.
How much steel does a slab need per cubic metre of concrete?
For ordinary residential work, roughly 70–110 kg per m³ for a slab, 100–200 for a beam, 100–250 for a column and 50–80 for an isolated footing. Those are ranges for cross-checking a schedule, not a design — a figure far outside them usually means a bar group has been missed or counted twice. The tool flags it either way.
How much wastage should I allow?
3–5% for straightforward work. The waste comes from offcuts — a 12 m bar cut into lengths that do not divide it evenly leaves an end — so heavily cranked or short-length work runs higher. Ordering in the lengths your schedule actually uses, where the supplier offers it, cuts this considerably.
Does this include binding wire and chairs?
No. Allow roughly 8–10 kg of binding wire per tonne of reinforcement, plus chairs, spacers and cover blocks. Lap lengths are not added either — if your schedule quotes cut lengths rather than laid lengths, add the laps before entering them here.