15M rebar is a Canadian metric reinforcing bar with a nominal diameter of 16.0 mm (0.630 in), a cross-sectional area of 200 mm² and a mass of 1.570 kg per metre. It is the closest Canadian match to US #5 (5/8 inch) bar, not 1/2 inch, and it carries exactly twice the steel of a 10M bar. On houses and small commercial buildings it is the size you see most in footings, foundation walls and dowels.
This guide pulls together what is specific to 15M: dimensions and weights by length, imperial comparisons, bend and hook sizes, typical laps, and the places it shows up in practice and in the Ontario Building Code.
15M rebar dimensions and weight
Nominal values are set by CSA G30.18 and published in the Reinforcing Steel Institute of Canada (RSIC) Manual of Standard Practice.
| Property | 15M value |
|---|---|
| Nominal diameter | 16.0 mm (0.630 in) |
| Cross-sectional area | 200 mm² (0.31 in²) |
| Nominal perimeter | 50.1 mm |
| Mass | 1.570 kg/m (1.055 lb/ft) |
| Weight of a 6 m bar | about 9.4 kg |
| Weight of a 12 m bar | about 18.8 kg |
| Weight of an 18 m bar | about 28.3 kg |
| Metres per tonne | about 637 m |
| Standard mill length (RSIC) | 18 m |
"16.0 mm" is the nominal diameter: the diameter of a plain round bar that would weigh the same per metre. A caliper across the ribs reads more. The full chart for all sizes is in our Canadian rebar size chart.
A useful mental model: one 15M equals two 10M in both area and weight. So "15M @ 400" and "10M @ 200" put the same amount of steel in a metre of wall or slab.
Is 15M rebar 5/8 or 1/2 inch?
15M lines up with 5/8 inch bar, not 1/2 inch:
| Bar | Diameter | Area |
|---|---|---|
| US #4 (1/2 in) | 12.7 mm | 129 mm² |
| Canadian 15M | 16.0 mm (about 5/8 in) | 200 mm² |
| US #5 (5/8 in) | 15.9 mm | about 199 mm² |
15M and #5 are within a fraction of a millimetre and a square millimetre of each other. They are still different products made to different standards (CSA G30.18 in Canada, ASTM in the US), with different markings and grade systems, so a straight swap on a Canadian job still goes through the engineer. 1/2 inch bar is a different story: a 15M has about 55% more steel than a #4, and replacing 15M with #4 at the same spacing would leave a member well short.
Watch the US soft-metric labels as well. A US "#16" bar is the #5 in metric naming, and a US "#13" is the #4. Neither is a Canadian bar size. Our Canadian vs US rebar sizes post sorts out the names.
Bending 15M: bend diameters and hooks
15M bends cleanly in a shop and is the most common size for L-bars, corner bars and footing dowels. CSA A23.1 sets minimum bend diameters, and the RSIC manual gives the matching hook dimensions:
| Item | 400W or 500W | 400R or 500R |
|---|---|---|
| Minimum finished bend diameter, standard hooks | 90 mm | 100 mm |
| 90° hook detailing allowance | 250 mm | 260 mm |
| 180° hook detailing allowance | 170 mm | 180 mm |
| 180° hook overall height (J) | 120 mm | 130 mm |
| Stirrup and tie bend diameter | 65 mm | 65 mm |
| 135° stirrup and tie hook allowance | 140 mm | 140 mm |
Field bending 15M by hand is hard work, and inconsistent bends make laps and cover hard to hold. That is one reason contractors order 15M corner bars and dowels pre-bent. See rebar hook lengths for the complete tables.
Lap and development length for 15M
Laps grow with bar diameter, so a 15M lap is noticeably longer than a 10M lap. The drawings govern, but for scale:
- CSA A23.3 simplified method, uncoated Grade 400 bar: a Class B tension lap of about 550 mm for bottom bars in 30 MPa concrete (about 720 mm for top bars), rising to about 600 mm for bottom bars in 25 MPa concrete. Development length for bottom bars in 30 MPa concrete is about 430 mm.
- Ontario Building Code, flat ICF walls: where Part 9 allows prescriptive ICF construction, 15M laps must be at least 650 mm.
The assumptions behind these numbers are spelled out in our lap splice length chart. Epoxy-coated 15M needs longer laps.
Where 15M rebar is used
In general practice, 15M is the workhorse bar for residential and light commercial concrete:
- Footings. Continuous bars in strip footings and both-way mats in pad footings. Our guide to rebar for footings in Ontario covers when footings need bar at all.
- Foundation walls. Vertical and horizontal bars in engineered walls, and the bond beam in reinforced block.
- Dowels. Footing-to-wall and slab-to-wall dowels, often bent.
- Grade beams and piers.
- Heavier slabs. Garage, shop and structural slabs where the design calls for more steel than 10M can sensibly deliver.
Where the Ontario Building Code names 15M
Engineered concrete under Part 4 takes its bar sizes from the design. The prescriptive Part 9 details in the 2024 OBC name 15M in several places:
- Reinforced concrete block foundation walls (Article 9.15.4.2.): where block walls must be reinforced, a continuous bond beam with at least one 15M bar runs along the top of the wall, at the sill and head of openings wider than 1.20 m, and at structurally connected floors. The vertical bars in Table 9.15.4.2.-B are 15M or 20M at spacings that depend on wall thickness, height and backfill.
- ICF dowels to the footing (Article 9.15.4.4.): one way to treat a flat ICF foundation wall as laterally supported at the bottom is dowels of 15M at no more than 1.2 m on centre (or 10M at 600 mm).
- ICF cold joints (Article 9.15.4.5.): cold joints in flat ICF foundation walls get at least one 15M bar at no more than 600 mm on centre, embedded at least 300 mm on each side.
- ICF wall reinforcement tables: some of the taller and more heavily backfilled cases in the vertical reinforcement tables move up to 15M.
- ICF lintels (Tables 9.20.17.4.-B and -C): span tables for lintels in loadbearing flat ICF walls with one or two 15M bottom bars.
Every one of these has conditions on height, thickness, openings and soil. Use the list to find the right article, then have your designer confirm the details.
15M vs 10M and 20M
- vs 10M: twice the area and weight. Stiffer, so it sags less between chairs, but harder to bend by hand and with longer laps. Our 10M rebar guide has the other half of the comparison.
- vs 20M: 20M is 19.5 mm and 300 mm², so one 20M carries 1.5 times the steel of a 15M. It turns up in heavier footings, columns and walls, and in some of the OBC block wall table entries.
Ordering 15M rebar
A typical foundation package is mostly 15M: straight footing bars, wall bars, corner L-bars and bent dowels, often with 10M ties or horizontals mixed in. Ordering from a detailed bar list means every piece arrives cut, bent and tagged by mark, so the crew can place it straight off the truck.
We detail, cut and bend 10M to 55M bar and deliver across the GTA and Ontario. Send us your drawings for a free take-off and quote, or browse our rebar products.
Frequently asked questions
What size is 15M rebar?
15M rebar has a nominal diameter of 16.0 mm (0.630 in), a cross-sectional area of 200 mm² and a mass of 1.570 kg per metre under CSA G30.18.
Is 15M rebar 5/8 or 1/2 inch?
It is the close cousin of 5/8 inch (US #5, 15.9 mm, about 199 mm²). It is much bigger than 1/2 inch (#4, 12.7 mm, 129 mm²), with about 55% more steel. 15M and #5 are still made to different standards, so follow the system on your drawings.
How thick is 15M rebar?
The nominal diameter is 16.0 mm. Measured across the ribs it is a little more, because the nominal diameter is the diameter of a plain bar with the same weight per metre.
How much does 15M rebar weigh?
1.570 kg per metre, or about 1.055 lb per foot. A 6 m bar weighs about 9.4 kg, a 12 m bar about 18.8 kg and an 18 m bar about 28.3 kg.
What is 15M rebar used for?
It is the everyday size for footings, foundation walls, grade beams, dowels and heavier slabs. In Part 9 of the Ontario Building Code it appears in reinforced block wall bond beams, ICF cold joints, ICF dowels and ICF lintels.
