GFRP (fiberglass) rebar sizes in Canada follow CSA S807, which identifies bars by a designated diameter and a nominal area rather than by steel's 10M, 15M naming. The common sizes are 10, 13, 15, 20, 22 and 25 mm, with nominal areas of 71, 129, 199, 284, 387 and 510 mm², the same areas as US #3 to #8 bar. GFRP weighs roughly a quarter to a third as much as steel: a 15 mm bar is about 0.43 to 0.53 kg per metre depending on the product and grade, against 1.570 kg/m for steel 15M. Weight is set by the manufacturer, so the data sheet for your actual product is the number to use.
GFRP rebar size chart
The designations and nominal areas below are the CSA S807 values as published on the data sheets of TUF-BAR, a Canadian GFRP manufacturer. The US labels are the equivalent bar numbers most suppliers also print.
| Designated diameter | US label | Nominal diameter (in) | Nominal area (mm²) | Nominal area (in²) |
|---|---|---|---|---|
| 10 mm | #3 | 3/8 | 71 | 0.110 |
| 13 mm | #4 | 1/2 | 129 | 0.200 |
| 15 mm | #5 | 5/8 | 199 | 0.308 |
| 20 mm | #6 | 3/4 | 284 | 0.440 |
| 22 mm | #7 | 7/8 | 387 | 0.600 |
| 25 mm | #8 | 1 | 510 | 0.791 |
These six cover most building work. Size ranges vary by manufacturer: V-ROD, another Canadian producer, lists its straight bars from a 6 mm (#2) bar up to a 32 mm (#10) bar. If your drawings call for a size outside the common range, check availability early.
GFRP sizes are not steel M sizes
Look at the first rows of that table next to steel:
| Size label | GFRP nominal area | Steel bar | Steel area |
|---|---|---|---|
| "10" GFRP | 71 mm² | 10M | 100 mm² |
| "15" GFRP | 199 mm² | 15M | 200 mm² |
| "20" GFRP | 284 mm² | 20M | 300 mm² |
| "25" GFRP | 510 mm² | 25M | 500 mm² |
A GFRP bar sold as "10 mm" or even "10M" has about 29% less area than steel 10M. The 15 and 25 sizes happen to land close to steel, and 20 is about 5% light. Because GFRP is designed under its own rules anyway (CSA S806 for buildings, CSA S6 for bridges), the bars on a GFRP drawing are not substitutes for steel bars of a similar name. Order to the designation on the drawings. Our post on Canadian vs US rebar sizes explains why the US-based numbers look metric.
GFRP rebar weight per metre and per foot
Unlike steel, there is no single weight table for GFRP. Weight depends on the glass content, the resin and the surface treatment, and higher-modulus grades tend to be heavier. Here are the published linear weights from TUF-BAR's straight bar data sheets for its three grades (45, 50 and 60 GPa products, which it lists as complying with CSA S807 Grades I, II and III):
| Size | 45 GPa (Grade I) | 50 GPa (Grade II) | 60 GPa (Grade III) | Steel bar for comparison |
|---|---|---|---|---|
| 10 mm (#3) | 0.150 kg/m | 0.162 kg/m | 0.195 kg/m | 10M: 0.785 kg/m |
| 13 mm (#4) | 0.259 kg/m | 0.279 kg/m | 0.339 kg/m | n/a |
| 15 mm (#5) | 0.433 kg/m | 0.467 kg/m | 0.526 kg/m | 15M: 1.570 kg/m |
| 20 mm (#6) | 0.611 kg/m | 0.660 kg/m | 0.742 kg/m | 20M: 2.355 kg/m |
| 22 mm (#7) | 0.816 kg/m | 0.883 kg/m | 0.990 kg/m | n/a |
| 25 mm (#8) | 1.105 kg/m | 1.193 kg/m | 1.309 kg/m | 25M: 3.925 kg/m |
And in imperial units, from the same data sheets:
| Size | 45 GPa | 50 GPa | 60 GPa |
|---|---|---|---|
| #3 (10 mm) | 0.10 lb/ft | 0.11 lb/ft | 0.13 lb/ft |
| #4 (13 mm) | 0.17 lb/ft | 0.19 lb/ft | 0.23 lb/ft |
| #5 (15 mm) | 0.29 lb/ft | 0.31 lb/ft | 0.35 lb/ft |
| #6 (20 mm) | 0.41 lb/ft | 0.44 lb/ft | 0.50 lb/ft |
| #7 (22 mm) | 0.55 lb/ft | 0.59 lb/ft | 0.67 lb/ft |
| #8 (25 mm) | 0.74 lb/ft | 0.80 lb/ft | 0.88 lb/ft |
Treat these as one manufacturer's figures, not industry constants. Another brand's 15 mm Grade III bar will be in the same neighbourhood but not identical. GFRP grades under CSA S807 are defined by minimum modulus of elasticity, and our CSA S807 and S806 explainer covers what the grades mean.
Nominal area vs measured area
GFRP data sheets often show two areas, and it is easy to grab the wrong one.
- Nominal area is the CSA S807 value for the designation (199 mm² for a 15 mm bar). This is the figure to use when you check a drawing, compare bars or calculate steel-equivalent quantities.
- Measured area is determined by test under CSA S807 Annex A and is larger, because it captures the whole bar including its surface treatment. TUF-BAR's sheets, for example, list a measured area of 235 mm² for its 15 mm Grade III bar against the 199 mm² nominal.
The measured area is part of how a bar is checked against the standard. It does not mean you get extra reinforcement. If a submittal or a substitution request quotes areas, make sure everyone is comparing nominal to nominal.
Calculating GFRP weight for an order
The method is the same as steel, with a different number per metre:
- Total the length of each size from the bar list, using developed lengths for bent bars.
- Multiply by the manufacturer's linear weight for that size and grade.
- Add up the sizes.
Example: 200 m of 15 mm Grade III bar at 0.526 kg/m is about 105 kg. The same length of steel 15M would weigh 314 kg.
That lower weight is a real advantage on site: bundles are lighter to unload and carry, and easier to handle during placing. It does not translate into a lower order cost by itself, because GFRP is not bought or designed like steel. Our rebar weight calculator covers the steel side if you need a comparison.
What else changes with size
A few things that depend on bar size are different for GFRP:
- Strength drops as diameter grows. Guaranteed tensile strength is lower for larger GFRP bars, which is part of why designers often prefer more, smaller bars. Our post on whether fiberglass rebar is stronger than steel goes into strength and stiffness.
- Bends are made at the factory. Bent GFRP bars are formed during manufacture and cannot be re-bent on site, and bend radii are set by the manufacturer's tooling for each size. See GFRP corners, L-bars and hooks.
- Straight lengths are set by the manufacturer and by shipping. Our guide to buying GFRP rebar in Ontario covers lengths, lead times and what to put on the order.
Getting GFRP sized and supplied
The size, grade and spacing of GFRP bar come from a GFRP design, not from converting a steel drawing. Once you have that, the practical questions are which manufacturer's product meets the specification, which sizes and bent shapes are needed, and how the bar list is put together.
We supply GFRP rebar alongside our steel rebar, detailed from your drawings. Ask us which sizes and grades we can supply for your job. Send us your drawings, or see our rebar products.
Frequently asked questions
What sizes does fiberglass rebar come in?
GFRP bars are identified by a designated diameter in millimetres under CSA S807. Common sizes are 10, 13, 15, 20, 22 and 25 mm, matching US #3 to #8, and some manufacturers make smaller and larger bars. Check the specific manufacturer's range.
How much does GFRP rebar weigh per metre?
It depends on the manufacturer and grade. One Canadian manufacturer's data sheets list a 15 mm bar at 0.433 kg/m in its 45 GPa product and 0.526 kg/m in its 60 GPa product, against 1.570 kg/m for steel 15M.
How much does fiberglass rebar weigh per foot?
For a 5/8 inch (15 mm) bar, roughly 0.29 to 0.35 lb/ft in one manufacturer's published range, depending on grade. Steel 15M is about 1.055 lb/ft. Always use the data sheet for the product you are buying.
Is 10 mm GFRP rebar the same as 10M steel rebar?
No. A 10 mm GFRP bar has a nominal area of 71 mm², the same as US #3. Steel 10M is 11.3 mm and 100 mm². GFRP sizes line up with US bar sizes, not Canadian M sizes.
Can you use a steel rebar weight calculator for GFRP?
No. Steel calculators use the density of steel. GFRP weighs roughly a quarter to a third as much, and the figure varies by product, so multiply your total length by the manufacturer's published linear weight.
