Canadian and US rebar use different size systems. Canadian bars are 10M to 55M, named for their approximate diameter in millimetres, while US bars are #3 to #18, named for their diameter in eighths of an inch. Several sizes line up closely (15M and #5, 20M and #6, 25M and #8, 35M and #11), but 10M has no close US match, and none of the pairs are identical. Use the charts below to convert, and treat any substitution as an engineering change.
For the full Canadian size chart with uses, see our rebar sizes guide. This post is the conversion reference.
US rebar sizes in metric
US bars are made to ASTM standards (A615 and A706 are the common ones). The bar number is the nominal diameter in eighths of an inch up to #8; from #9 up the numbers are kept by convention and the diameters no longer match an exact eighth.
| US bar | Nominal diameter (in) | Diameter (mm) | Area (in²) | Area (mm²) | Weight (lb/ft) | Weight (kg/m) |
|---|---|---|---|---|---|---|
| #3 | 0.375 (3/8) | 9.5 | 0.11 | 71 | 0.376 | 0.560 |
| #4 | 0.500 (1/2) | 12.7 | 0.20 | 129 | 0.668 | 0.994 |
| #5 | 0.625 (5/8) | 15.9 | 0.31 | 200 | 1.043 | 1.552 |
| #6 | 0.750 (3/4) | 19.1 | 0.44 | 284 | 1.502 | 2.235 |
| #7 | 0.875 (7/8) | 22.2 | 0.60 | 387 | 2.044 | 3.042 |
| #8 | 1.000 (1) | 25.4 | 0.79 | 510 | 2.670 | 3.973 |
| #9 | 1.128 | 28.7 | 1.00 | 645 | 3.400 | 5.060 |
| #10 | 1.270 | 32.3 | 1.27 | 819 | 4.303 | 6.404 |
| #11 | 1.410 | 35.8 | 1.56 | 1,006 | 5.313 | 7.907 |
| #14 | 1.693 | 43.0 | 2.25 | 1,452 | 7.650 | 11.384 |
| #18 | 2.257 | 57.3 | 4.00 | 2,581 | 13.600 | 20.239 |
Metric weights are converted from the published lb/ft values and rounded.
Canadian rebar sizes in imperial
Canadian bars are made to CSA G30.18. The areas are round metric numbers, which makes Canadian bars easy to work with in design.
| Canadian bar | Diameter (mm) | Diameter (in) | Area (mm²) | Area (in²) | Weight (kg/m) | Weight (lb/ft) |
|---|---|---|---|---|---|---|
| 10M | 11.3 | 0.445 | 100 | 0.16 | 0.785 | 0.527 |
| 15M | 16.0 | 0.630 | 200 | 0.31 | 1.570 | 1.055 |
| 20M | 19.5 | 0.768 | 300 | 0.47 | 2.355 | 1.582 |
| 25M | 25.2 | 0.992 | 500 | 0.78 | 3.925 | 2.637 |
| 30M | 29.9 | 1.177 | 700 | 1.09 | 5.495 | 3.692 |
| 35M | 35.7 | 1.406 | 1,000 | 1.55 | 7.850 | 5.275 |
| 45M | 43.7 | 1.720 | 1,500 | 2.33 | 11.775 | 7.912 |
| 55M | 56.4 | 2.220 | 2,500 | 3.88 | 19.625 | 13.187 |
Nearest equivalent sizes
This is the chart most people are looking for. "Nearest" is based on cross-sectional area, which is what carries load, and the last column shows how far apart the two bars are.
| Canadian bar | Nearest US bar | Canadian area | US area | Difference in steel area |
|---|---|---|---|---|
| 10M | between #3 and #4 | 100 mm² | 71 / 129 mm² | 10M has about 41% more than #3 and 22% less than #4 |
| 15M | #5 | 200 mm² | 200 mm² | essentially equal |
| 20M | #6 | 300 mm² | 284 mm² | 20M about 6% more |
| 25M | #8 | 500 mm² | 510 mm² | 25M about 2% less |
| 30M | #9 | 700 mm² | 645 mm² | 30M about 9% more |
| 35M | #11 | 1,000 mm² | 1,006 mm² | essentially equal |
| 45M | #14 | 1,500 mm² | 1,452 mm² | 45M about 3% more |
| 55M | #18 | 2,500 mm² | 2,581 mm² | 55M about 3% less |
Two US sizes have no Canadian neighbour at all: #7 (387 mm²) falls between 20M and 25M, and #10 (819 mm²) falls between 30M and 35M.
Quick answers to the common searches:
- 3/8 in rebar is #3. Nearest Canadian: 10M, which is bigger.
- 1/2 in rebar is #4. Nearest Canadian: 10M (smaller) or 15M (bigger).
- 5/8 in rebar is #5. Nearest Canadian: 15M.
- 3/4 in rebar is #6. Nearest Canadian: 20M.
- 7/8 in rebar is #7. No close Canadian match.
- 1 in rebar is #8. Nearest Canadian: 25M.
The soft-metric naming trap
US mills also mark bars with soft-metric sizes, which are the same US bars with metric names: #10 (= #3), #13 (= #4), #16 (= #5), #19 (= #6), #22 (= #7), #25 (= #8), #29 (= #9), #32 (= #10), #36 (= #11), #43 (= #14) and #57 (= #18).
These names look like Canadian sizes, and that causes real mistakes:
- A US "#10" metric bar is the #3, a 9.5 mm bar, noticeably smaller than a Canadian 10M (11.3 mm).
- A US imperial #10 is a 32.3 mm bar, much larger than a 10M.
- A US "#25" metric bar is the #8, close to a Canadian 25M but not the same bar.
The Canadian "M" suffix is the tell. If a document or bar tag shows a size without the M, check whether it is a US imperial number or a US soft-metric number before you order or place anything.
Substituting US bars on a Canadian job
Substitutions come up when working from US details, using US-sourced product data, or when a specific size is hard to get. The rules of thumb engineers use:
1. Match steel area per metre, not bar count. Convert the spacing, not just the size. Some examples:
| US callout | Steel area per metre | Canadian layout | Steel area per metre |
|---|---|---|---|
| #4 @ 16 in | 318 mm²/m | 10M @ 300 | 333 mm²/m |
| #4 @ 12 in | 423 mm²/m | 10M @ 230 | 435 mm²/m |
| #5 @ 12 in | 656 mm²/m | 15M @ 300 | 667 mm²/m |
| #6 @ 12 in | 931 mm²/m | 15M @ 200 | 1,000 mm²/m |
2. Recheck lap and development lengths. These depend on bar diameter and grade, and Canadian lengths come from CSA A23.3, not ACI 318. Our development length guide and lap splice chart give the Canadian numbers.
3. Recheck cover and clear spacing. A bigger bar eats into cover and the gap between bars.
4. Check the grade. US Grade 60 (metric Grade 420) is close to Canadian 400 grades but not identical, and only some US bars match the weldability and ductility controls of 400W. See our guide to Canadian rebar grades.
5. Get it approved. Any size, spacing or grade change goes to the engineer of record. Detailing conventions also differ between the two countries, which our post on ACI vs CSA rebar detailing covers.
Getting the right bar for your drawings
If your drawings are in US sizes but the job is in Ontario, the cleanest route is to have the engineer restate the reinforcement in metric bars before it is detailed. Once the drawings are in Canadian sizes, the bar list, laps, hooks and bends all follow Canadian practice.
We supply Canadian metric rebar in all standard sizes from 10M to 55M, cut, bent and tagged to your bar lists. Send us your drawings for a free take-off and quote, or see our rebar products and size chart.
Frequently asked questions
What is the US equivalent of 15M rebar?
US #5 (5/8 in) is the nearest match. 15M is 16.0 mm with a 200 mm² area and #5 is 15.9 mm with a 200 mm² (0.31 in²) area, so the two are almost identical in size. They are still made to different standards and grades.
What rebar size is 3/4 inch?
3/4 in rebar is US #6, with a nominal diameter of 19.1 mm and an area of 284 mm². The nearest Canadian bar is 20M (19.5 mm, 300 mm²).
What rebar size is 1 inch?
1 in rebar is US #8, with a nominal diameter of 25.4 mm and an area of 510 mm². The nearest Canadian bar is 25M (25.2 mm, 500 mm²).
Is 10M rebar the same as #3 or #4?
Neither. 10M is 11.3 mm with a 100 mm² area, between #3 (9.5 mm, 71 mm²) and #4 (12.7 mm, 129 mm²). Swapping 10M for either changes the amount of steel, so it needs the engineer's approval.
Is US #13 rebar the same as Canadian 10M?
No. #13 is the soft-metric name for US #4 (12.7 mm). US soft-metric names (#10, #13, #16 and so on) look like Canadian sizes but refer to US bars, and #10 metric is the US #3, smaller than a Canadian 10M.
