Rebar Calculator
Find how many 10M, 15M or 20M bars of reinforcing steel a footing, wall or slab needs. See what they weigh and cost.
Measure your job
Laps: 450 mm for 10M and 650 mm for 15M, from the building code (Part 9) for ICF walls. For 20M there is no code number: type the lap from your drawings.
Your answer
10M rebar. 2 bars side by side.
We cut short pieces from whole bars. We don't join cut-off ends again, so you may have a few spare ends.
This answer is a guide. Bars, spacing and laps must follow your plans. Check your local building rules or ask a builder or engineer.
What it costs
Middle price per bar at Canadian building-supply stores (Oct 2026), before tax. 10M: 5 stores for 20 ft, only 2 for 10 ft. 15M: only 3.
Quick answers
- 10M rebar weight
- 0.785 kg per metre. A 6 m bar weighs 4.71 kg.
- 15M rebar weight
- 1.57 kg per metre. A 6 m bar weighs 9.42 kg.
- A "20 ft" bar
- A "20 ft" bar in a store is usually a 6 m bar, 19 ft 8 in long.
- How much to overlap
- 450 mm for 10M and 650 mm for 15M. Those are the code's numbers for ICF walls.
- Rebar price
- About $8.75 for a 10M bar of 20 ft, the middle of 5 stores. Before tax.
How to work it out
- Count the bars your plans show side by side, and measure how long each run is.
- A run longer than one bar needs two or more bars, joined with a lap.
- Work out the full bars in each run. Cut the last short piece from a spare bar.
- Multiply by the number of runs. Short pieces can share one bar.
Footing: 2 runs of 10M, 40 ft long. Bars are 6 m (19 ft 8 in). Lap 450 mm (17.7 in)
One run: 3 bars with 2 laps = 42.95 ft of bar
That is 2 full bars and a 3.58 ft piece. 5 pieces fit in one bar
2 × 2 full bars + 1 for the pieces = 5 bars
5 × $8.75 = $43.75 before tax
Canadian bar sizes and weights
Rebar is reinforcement steel. Canada uses metric bars made to CSA G30.18. The name is close to the width: a 10M bar is 11.3 mm across, with 100 square mm of steel.
| Bar | Across | Steel | kg per metre | kg per 6 m bar | lb per foot |
|---|---|---|---|---|---|
| 10M | 11.3 mm | 100 mm² | 0.785 | 4.71 | 0.528 |
| 15M | 16 mm | 200 mm² | 1.57 | 9.42 | 1.055 |
| 20M | 19.5 mm | 300 mm² | 2.355 | 14.13 | 1.583 |
| 25M | 25.2 mm | 500 mm² | 3.925 | 23.55 | 2.638 |
From the OCCDC guide (Ontario concrete group). A 6 m bar is sold as 20 ft.
Don't mix them up with US sizes
Some charts call 10M "#3". That is wrong: by our sums, 10M has about 40% more steel. 15M is close to US #5.
Stores sell a 6 m bar as a "20 ft" bar. It is really 19 ft 8 in long. Short bars are 3 m (10 ft). We found no 12 m bars in stores.
Bars come in grades 400R, 500R, 400W, 500W. Grade 400 is marked with "400" or one offset line.
Rebar in a bundle
One Canadian seller bundles 10M in 192 bars of 6 m, about 900 kg. Bundle sizes vary by mill and seller. We found no bundle count for 15M.
What rebar costs in Canada
| Bar | 20 ft (6 m) bar | 10 ft (3 m) bar | Per metre, long bar | Ontario stores, per foot |
|---|---|---|---|---|
| 10M | $8.75 (5) | $4.60 (2) | $1.46 | $0.60 (2) |
| 15M | $16.99 (3) | $8.81 (3) | $2.83 | $1.15 (3) |
Stores in brackets. Bar prices: building-supply stores in Ontario, Manitoba, Alberta and BC; some were sale prices. Per foot: Ontario stores.
Short bars cost more per metre. A 10 ft 10M bar works out to $1.53 a metre.
Only 3 stores priced 15M, so treat it as rough. We found no price in the Atlantic provinces.
Big orders go by weight. Multiply the metres of bar by the kg per metre. One tonne of 10M is about 1,274 m of bar.
Lap splices and concrete cover
Where two bars join, they overlap. This is called a lap splice. The only code numbers we found are for ICF walls. So use them as a guide, and follow your drawings.
| Bar | Code (ICF walls) | One engineer's notes |
|---|---|---|
| 10M | 450 mm (17.7 in) | 450–550 mm |
| 15M | 650 mm (25.6 in) | 600–800 mm |
| 20M | none found | 750–950 mm |
Code: BC Building Code 2018, 9.3.1.1.(4), for flat ICF walls only. Engineer's notes: one City of Coquitlam project; the longer figure is for top bars.
How deep the bars sit: concrete cover
- Poured against the ground (footings): 75 mm.
- Driveways and garage floors with road salt: 60 mm.
- Formed, then open to weather or soil: 50 mm.
- Inside, kept dry: 20 mm.
These come from a city spec, a farm builders' guide and Concrete Alberta. The full standard (CSA A23.1) is not free.
When does concrete need rebar?
The building code (Part 9) covers houses. It has no rebar rule for footings or floor slabs. Fully reinforced concrete must be designed by an engineer. This calculator doesn't size cages for columns or beams.
The 2024 BC code added a new choice for foundation walls: 10M bars at 600 mm apart. We read only the list of changes.
Home driveways and garage floors don't need rebar or mesh, says Concrete Manitoba. To put steel in anyway, the rebar for slab calculator counts a grid of bars, or wire mesh. In a driveway grid, Concrete Alberta says bars should be tied at every second crossing.
Does fibre (fiber) concrete need rebar?
Fibres are mixed into the concrete. Concrete Alberta says macro synthetic fibres may be used in place of rebar in a driveway. Concrete Manitoba says they are not required in home driveways and garage floors.
Why put rebar in concrete?
In a flat slab, steel or fibres won't stop cracks, says Concrete Manitoba. But they can mean fewer control joints, or joints spaced farther apart. In concrete built to carry big loads, an engineer sets the steel.
How much rebar do I need for a footing?
Part 9 sets no bars for a footing, so take the count from your plans. In the calculator, pick "Footing or wall". Type the footing's length and the bars side by side.
Say your plans show 2 bars of 10M along a 40 ft footing. With 450 mm laps, that takes 5 bars of 20 ft. They weigh about 24 kg.
Bars in a footing or wall carry weight. Check your local building rules or ask a builder or engineer.
Questions people ask
How much does 10M rebar weigh?
0.785 kg per metre (0.528 lb per foot). A 6 m bar, sold as "20 ft", weighs 4.71 kg.
How much does 15M rebar weigh?
1.57 kg per metre (1.055 lb per foot). A 6 m bar weighs 9.42 kg.
How much does 20M rebar weigh?
2.355 kg per metre. A 6 m bar weighs 14.13 kg.
How much should rebar overlap?
The code gives 450 mm for 10M and 650 mm for 15M, for ICF walls. Those are the only code laps we found, so check your drawings.
How do I work out how much rebar I need?
Count the runs and measure each one. The formula for one run is its length plus the laps, divided by the bar length you buy. Round up, then multiply by the runs.
How do I calculate rebar spacing?
Your plans set the spacing. To count bars, take the width in mm and subtract 75 mm for each edge. Divide by the spacing, drop the part, then add 1.
Is 10M rebar the same as #3 or #4?
No. 10M sits between US #3 and #4. By our sums it has about 40% more steel than #3. 15M is close to US #5.
How much is rebar in Canada?
About $8.75 for 10M and $16.99 for 15M, per 20 ft bar. Middle prices from 5 stores (10M) and only 3 (15M), before tax.
Where our numbers come from
- Rebar sizes and mesh: OCCDC Reinforced Concrete Reference Guide (2021)
- Rebar lengths and weights: 2AZ Group supplier guide (Ontario)
- Rebar lengths: Canadian Super Steel (Mississauga)
- Rebar prices: Canadian building-supply stores (Oct 2026)
- Store prices: Ontario Home Depot, RONA, Home Hardware and Chamberlain Timber Mart (Oct 2026)
- Concrete strength and site mixes: BC Building Code 2018, Section 9.3 (Part 9)
- Footings and piers: BC Building Code 2018, Section 9.15
- What changed in 2024: BOABC list of BC Building Code revisions (footings and foundations)
- Rebar laps (cross-check): one engineer's drawing notes, City of Coquitlam tender
- Rebar cover: City of Nanaimo engineering standards, Section 11
- Cover and air: Canadian Farm Builders Association concrete guide
- Driveways, joints and slope: Concrete Alberta flatwork guide
- Driveways and garage slabs: Concrete Manitoba (thickness, base, steel)
- Kilrich Building Centres: 10M (10 mm) rebar, 6 m bars, bundle of 192 pieces
Made by BuildersCount. Last checked 4 Oct 2026.
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