Utility
Steel Rebar Weight Calculator
Add up a bar bending schedule: bars by diameter, cut length and count, giving the weight of each size, the number of 12 m bars to buy, and the tonnage to order. Mass per metre derived from the geometry, not copied off a chart.
The schedule
One row per bar mark. Enter the cut length with laps, hooks and bends already in it — allowances for those vary by detail and by standard, so the tool takes the length you have rather than inventing one.
Weight: 220.2 kg
Weight: 170.5 kg
Weight: 66.3 kg
Offcuts that cannot be used elsewhere, and the ends lost to cutting. Two to five per cent is usual. The stock-bar count assumes offcuts can be reused, which a site rarely manages — this is where that difference lives.
What to order
Order this much steel
471 kg
0.471 t · schedule: 457 kg
By diameter
| Diameter | kg/m | Bars | Total length (m) | 12 m bars | Weight |
|---|---|---|---|---|---|
| 8 mm | 0.395 | 120 | 168 | 14 | 66.3 |
| 12 mm | 0.888 | 40 | 248 | 21 | 220.2 |
| 16 mm | 1.578 | 24 | 108 | 9 | 170.5 |
Full bars are the total length for that size divided by 12 m, rounded up. Nobody orders "the slab's steel" — steel is bought by diameter, in full lengths. Rebar weight chart
The sanity check
A schedule can be out by a factor of ten and still look right. Steel as a percentage of concrete volume is the check an estimator does by instinct: ordinary reinforced work sits between about 0.7% and 2.5%, slabs at the light end and columns, rafts and heavily loaded members at the heavy one. Enter the concrete volume from the same drawing.
Enter the concrete volume to see the steel percentage.
How to use it
- Add a row for each bar mark: diameter, how many, and the cut length of one.
- Put laps, hooks and bends inside the cut length — the tool does not add them.
- Set a wastage allowance for offcuts you cannot use elsewhere.
- Read the tonnage to order, and the by-diameter table for what to ask the merchant for.
- Enter the concrete volume for the same element to check the steel percentage against the ordinary range.
How it works
Each row weighs its bar count × cut length × mass per metre for that diameter.
Mass per metre is (π/4) × d² × 7850, which for d in millimetres reduces to d²/162.196 kg/m. The same figures appear on the rebar weight chart, computed by the same code.
Rows are regrouped by diameter, and the full bars for each size are the total length divided by 12 m, rounded up.
The wastage allowance is added to the order weight and left off the schedule weight, so both figures stay visible.
The steel percentage converts the schedule weight to a volume at 7850 kg/m³ and compares it with the concrete volume — a percentage of volume, not of weight.
Common questions
Do I add laps and hooks, or does the tool?
You do, inside the cut length. Allowances differ by standard, by detail and by what the engineer has specified — a hook is quoted at 8d, 9d and 16d in different places — so a tool that picked one silently would put a figure into your steel bill that nobody chose. A real bar bending schedule already carries cut lengths, which is the form this takes.
Why group by diameter?
Because that is how steel is bought. A merchant sells you so many tonnes of 12 mm and so many of 16, in twelve-metre lengths; nobody quotes for "the slab's steel". The by-diameter table is the one you can actually order from, and the per-metre column is there so you can check any row against the chart.
Rebar weight chart →Is the 12 m bar count realistic?
It is the estimate, not the cutting plan. It divides the total length for each size by twelve and rounds up, which assumes an offcut from one bar can serve another cut. On site that is often impossible, and the wastage allowance is where the difference belongs. For a real cutting schedule you need the individual lengths, not the total.
Where does the weight per metre come from?
From the geometry: a bar is a steel cylinder, so its mass per metre is its cross-sectional area times 7850 kg/m³, which reduces to d²/162.196. It is computed here rather than read from a table, which matters because two of the figures in general circulation disagree with the geometry in the last decimal — in opposite directions, so they cannot both be right.
Rebar weight chart →Does this include the concrete?
No. The concrete volume calculator does that, and it deliberately gives the gross volume of the element without deducting the steel — reinforcement displaces roughly one to two per cent, which is inside the wastage allowance and in the direction of ordering slightly too much.
Concrete volume calculator →