PreConstruct AIFree calculator
Rebar weight calculator and size chart
Canadian metric bars from 10M to 55M and imperial bars from #3 to #11. Weigh bars by their length, or lay out a slab mat at a spacing each way — in metres, feet, kilograms, pounds, tonnes and tons.
Weight
108.8 kg
239.87 lb
Length
69.3 m
227.36 ft
Tonnes
0.11 t
0.12 US tons
15M weighs
1.57 kg/m
1.05 lb/ft
The working
- 10 bars × 6 m = 60 m
- 60 m + laps of 10 per cent + waste of 5 per cent = 69.3 m
- 69.3 m × 1.57 kg/m (15M) = 108.8 kg
A starting figure, not an engineered quantity. Sizes, reinforcing and code requirements come from your drawings, your specifications and your engineer — check them before you order.
Where a calculator stops
This does one run, from numbers you type. A bid is every run on every sheet.
- — It doesn't read the drawing set or its schedules
- — It doesn't measure on the PDF or keep the lengths
- — It doesn't show what an addendum changed
- — It doesn't price, add labour or build a proposal
Canadian metric bars — CSA G30.18
The number is the nominal diameter rounded to five millimetres: a 15M bar is 16.0 mm across.
| Bar | Diameter (mm) | Area (mm²) | Mass (kg/m) |
|---|---|---|---|
| 10M | 11.3 | 100 | 0.785 |
| 15M | 16.0 | 200 | 1.570 |
| 20M | 19.5 | 300 | 2.355 |
| 25M | 25.2 | 500 | 3.925 |
| 30M | 29.9 | 700 | 5.495 |
| 35M | 35.7 | 1000 | 7.850 |
| 45M | 43.7 | 1500 | 11.775 |
| 55M | 56.4 | 2500 | 19.625 |
Imperial bars — ASTM A615
The number is the diameter in eighths of an inch: a #5 bar is ⅝ in.
| Bar | Diameter (in) | Area (in²) | Weight (lb/ft) |
|---|---|---|---|
| #3 | 0.375 | 0.11 | 0.376 |
| #4 | 0.500 | 0.20 | 0.668 |
| #5 | 0.625 | 0.31 | 1.043 |
| #6 | 0.750 | 0.44 | 1.502 |
| #7 | 0.875 | 0.60 | 2.044 |
| #8 | 1.000 | 0.79 | 2.670 |
| #9 | 1.128 | 1.00 | 3.400 |
| #10 | 1.270 | 1.27 | 4.303 |
| #11 | 1.410 | 1.56 | 5.313 |
Bars by length
bars × length × (1 + laps) × (1 + waste) × kg/m = kg. Ten 15M bars 6 m long are 60 m, or 94.2 kg before laps and waste.
A mat each way
For a slab at a spacing each way, the bars running one way are the other dimension ÷ spacing + 1, each as long as the slab: (W ÷ s + 1) × L + (L ÷ s + 1) × W. Cover at the edges and hooks shorten or lengthen them — the drawings give both.
Questions estimators ask
- How much does 15M rebar weigh?
- 15M rebar weighs 1.570 kg per metre under CSA G30.18 — about 1.05 pounds per foot. A 6 m bar is 9.42 kg.
- What is the difference between 10M and #3 rebar?
- 10M is a Canadian metric bar with an 11.3 mm nominal diameter and a mass of 0.785 kg/m. #3 is an imperial bar, 0.375 in (9.5 mm) across, at 0.376 lb/ft (0.56 kg/m). They are close but not interchangeable — use the size the drawings call for.
- How do I convert rebar from kg per metre to pounds per foot?
- Multiply kg per metre by 0.672. For example, 1.570 kg/m (15M) is 1.055 lb/ft.
- How much should I add for laps?
- Lap lengths come from the structural drawings and the reinforcing standard for the bar size and concrete strength. Estimators often carry a percentage for laps on continuous bars; type the allowance your drawings support.
Stop retyping sizes into a calculator
On PreConstruct AI you measure on the PDF, type the sizes the drawings print, and the concrete, forms, bars, board and stringers come out with the arithmetic beside every line — in imperial, metric or both. Your first bid is free, with no card.