Y12, T12, H12 and N12 all describe a 12 mm deformed reinforcing bar; the letter in front tells you the steel type or grade under the country's system, and the number is the nominal diameter in millimetres. A 12 mm bar has about 113 mm² of area and weighs about 0.888 kg/m whatever its prefix. D10 is the exception that trips people up: under Japan's JIS system it is a 9.53 mm bar, not a 10 mm one. None of these sizes is the same as a Canadian M bar, so on an Ontario job they have to be converted.
What the letters mean
Most of the world outside North America sizes rebar by its diameter in whole millimetres: 8, 10, 12, 16, 20, 25, 32 and so on. Drawings add a letter in front to say what kind of bar it is. The letters are not universal, which is why the same 12 mm bar can show up as Y12, T12, H12 or N12.
| Label | Where you see it | What it means |
|---|---|---|
| H (H12) | UK bar schedules to BS 8666 | High-yield bar to BS 4449, grade B500A, B500B or B500C |
| B or C (B16, C16) | UK schedules where ductility matters | B500B or B500C only (B), or B500C only (C) |
| T (T12) | Older UK drawings, still common shorthand | High-tensile deformed bar; the old grade 460 designation, now used informally for B500 bar |
| R (R10) | Older UK and Commonwealth drawings | Plain round mild steel bar |
| Y (Y12) | Older drawings in several countries, including Australia before N bars | High-yield deformed bar |
| N (N16) | Australia and New Zealand, AS/NZS 4671 | Deformed bar, 500 MPa, normal ductility (full name D500N16) |
| D (D10) | Japan (JIS G3112), Korea; also shorthand for "deformed" elsewhere | Deformed bar; under JIS the number is a rounded size, not the exact diameter |
| M (15M) | Canada, CSA G30.18 | Metric bar; the number is the rounded nominal diameter |
The practical rule: read the number as the diameter, then check the drawing's notes or bar schedule key for what the letter means on that project. The grade matters as much as the size when you convert.
In Australia, the full AS/NZS 4671 designation spells out shape, strength, ductility and diameter: D500N12 is a deformed bar, 500 MPa, normal ductility, 12 mm, usually shortened to N12. The older Y bars were a lower-strength high-yield bar that the N designation replaced.
In the UK, bar schedules follow BS 8666, which uses H as the general high-yield type. T comes from the earlier version of the standard, when it referred to grade 460 bar, and many detailers still write T out of habit.
Metric bar sizes and weights (Y, T, H, N and B500 bars)
For bars sized in whole millimetres, the area and weight follow directly from the diameter. These are the nominal values listed in EN 10080, the European product standard; Australian N bars use the same values for the sizes they share.
| Diameter | Common labels | Area (mm²) | Weight (kg/m) |
|---|---|---|---|
| 6 mm | H6, R6 | 28.3 | 0.222 |
| 8 mm | H8, T8, Y8 | 50.3 | 0.395 |
| 10 mm | H10, T10, Y10 | 78.5 | 0.617 |
| 12 mm | H12, T12, Y12, N12 | 113 | 0.888 |
| 16 mm | H16, T16, Y16, N16 | 201 | 1.58 |
| 20 mm | H20, T20, Y20, N20 | 314 | 2.47 |
| 24 mm | N24 (Australia) | 452 | 3.55 |
| 25 mm | H25, T25, Y25 | 491 | 3.85 |
| 28 mm | N28 | 616 | 4.83 |
| 32 mm | H32, T32, N32 | 804 | 6.31 |
| 36 mm | N36 (Australia) | 1,020 | 7.99 |
| 40 mm | H40, T40 | 1,257 | 9.86 |
| 50 mm | Large heavy civil bars | 1,963 | 15.4 |
Australia uses 24, 28 and 36 mm bars where Europe and the UK use 25 mm, so an N24 is not the same as a 25 mm bar.
A handy shortcut for any bar sized in whole millimetres: weight in kg/m is the diameter squared divided by 162. For 12 mm, 144 ÷ 162 = 0.889 kg/m. For 20 mm, 400 ÷ 162 = 2.47 kg/m. The same steel density sits behind the Canadian rebar weight formula.
JIS D sizes (D10, D13, D16 and up)
Japan's JIS G3112 names deformed bars with a D and a rounded size. The nominal diameters are close to the US eighth-inch sizes rather than whole millimetres, which is why D10 is really 9.53 mm. Korea's KS D 3504 uses the same D designations, with matching values for the common sizes.
| JIS bar | Nominal diameter (mm) | Area (mm²) | Weight (kg/m) | Same size as |
|---|---|---|---|---|
| D10 | 9.53 | 71.33 | 0.560 | US #3 |
| D13 | 12.7 | 126.7 | 0.995 | US #4 |
| D16 | 15.9 | 198.6 | 1.56 | US #5 |
| D19 | 19.1 | 286.5 | 2.25 | US #6 |
| D22 | 22.2 | 387.1 | 3.04 | US #7 |
| D25 | 25.4 | 506.7 | 3.98 | US #8 |
| D29 | 28.6 | 642.4 | 5.04 | close to US #9 |
| D32 | 31.8 | 794.2 | 6.23 | close to US #10 |
So if someone asks for "D10 rebar weight", the first question is whose D10. A JIS D10 weighs 0.560 kg/m; a 10 mm deformed bar labelled D10 on a European or Australian drawing weighs 0.617 kg/m. Our post on Canadian vs US rebar sizes covers the US numbered bars that line up with the JIS sizes.
Converting to Canadian M bars
Canadian bars are made to CSA G30.18 in eight sizes, 10M to 55M, each with a round-number area. The Canadian size chart has the full dimensions. Here is how the common international sizes line up, matched on cross-sectional area, which is what carries load.
| International bar | Area (mm²) | Nearest Canadian bar | Canadian area (mm²) | How close |
|---|---|---|---|---|
| 10 mm (Y10, T10, H10) | 78.5 | 10M | 100 | 10M has about 27% more steel |
| 12 mm (Y12, T12, N12) | 113 | 10M | 100 | 10M has about 12% less steel |
| JIS D13 | 126.7 | 10M or 15M | 100 / 200 | No close match |
| 16 mm (Y16, N16, T16) | 201 | 15M | 200 | Essentially equal |
| 20 mm (Y20, N20, T20) | 314 | 20M | 300 | 20M has about 5% less |
| 25 mm (Y25, T25, H25) | 491 | 25M | 500 | 25M has about 2% more |
| 28 mm and 32 mm | 616 / 804 | 30M | 700 | Neither is close |
| 36 mm (N36) | 1,020 | 35M | 1,000 | 35M about 2% less |
| 40 mm | 1,257 | 35M or 45M | 1,000 / 1,500 | No close match |
The 12 mm bar is the one that causes the most trouble. It is the everyday bar in much of the world, and a Canadian 10M is smaller. Replacing Y12 at 200 mm with 10M at 200 mm puts about 12% less steel in the slab or wall.
How to handle an international drawing on an Ontario job
Drawings from overseas designers, imported precast or modular units, and owners working from a design done elsewhere all bring these labels into Ontario. A few rules keep the job out of trouble:
- Have the engineer restate the bars in Canadian sizes. The design has to meet the 2024 Ontario Building Code, which references CSA A23.3 for concrete design and CSA G30.18 for the bars themselves. An engineer licensed in Ontario should issue the revised reinforcement, not the site or the supplier.
- Convert by steel area per metre, not bar for bar. Y12 at 200 mm gives about 565 mm² per metre. 10M at 175 mm gives about 571 mm²/m, which is the closer layout. Our rebar area and spacing table makes these swaps quick.
- Check the grade. B500 and Australian 500N bars have a higher specified yield strength than Canadian 400W, the common grade here. Converting a 500 MPa design to 400 MPa bar usually needs more steel, which is another reason the engineer does the conversion. See our guide to Canadian rebar grades.
- Recalculate laps, hooks and cover. Lap and development lengths come from CSA A23.3, not the original code, and bend diameters follow Canadian practice. Our lap splice length chart gives typical Canadian values.
- Watch mixed-unit schedules. A bar schedule that says "10" could mean a 10 mm bar, a JIS D10 (9.53 mm) or a Canadian 10M (11.3 mm). Confirm before anything is cut.
Getting the bar list done right
Once the reinforcement is restated in Canadian bars, it is detailed, cut and bent like any other Ontario job. We detail and fabricate 10M to 55M rebar to CSA G30.18, with bar lists and placing drawings prepared from your structural drawings, and deliver across the GTA and Ontario.
Send us your drawings, including the original schedule and the engineer's revised bar callouts, for a free take-off and quote. You can also see our rebar products and size chart.
Frequently asked questions
What size is Y12 rebar?
Y12 is a 12 mm deformed high-yield bar. It has a cross-sectional area of about 113 mm² and weighs about 0.888 kg per metre. The nearest Canadian bar is 10M (100 mm²), which is smaller.
How much does N12 or T12 rebar weigh?
Any 12 mm steel bar, whether it is labelled N12, T12, H12 or Y12, weighs about 0.888 kg per metre. The letter describes the steel type or grade, not the size.
What is D10 rebar?
It depends on the source. Under the Japanese JIS standard, D10 is a deformed bar with a 9.53 mm nominal diameter weighing 0.560 kg/m, the same size as US #3. Elsewhere D10 is often shorthand for a 10 mm deformed bar, which weighs about 0.617 kg/m.
What size is Y16 rebar in Canada?
Y16 is a 16 mm bar with about 201 mm² of area. Canadian 15M has a 16.0 mm nominal diameter and a 200 mm² area, so it is the closest match of any pair, though the grades and standards still differ.
Does Eurocode set rebar sizes?
No. Eurocode 2 is a design code. Bar sizes and properties come from product standards: the European standard EN 10080 lists nominal diameters from 6 mm to 50 mm, and national standards such as the UK's BS 4449 cover the bars used there.
