GFRP rebar calculator
Read a steel bar size from any drawing standard and find the closest GFRP bar, work out the ACI CODE-440.11-22 design values from the bar's certificate, and estimate the shipping weight.
- Bar systems
- ASTM · EN · AS/NZS · CSA
- GFRP sizes
- Ø6–Ø36 mm
- Design basis
- ACI CODE-440.11-22
1. Match a steel bar size
A size match only. GFRP is about a quarter as stiff as steel, so bar area, spacing, cover and laps are redesigned by the engineer of record.
2. Design values to ACI CODE-440.11-22
Enter the guaranteed tensile strength and modulus from the certificate of the bar offered for the project. The tool does not assume a grade.
3. Weight for shipping
Nominal area × density. The supplier's declared unit mass replaces this once a grade is offered.
0.422 kg/m; 100 bars × 6 m ≈ 253 kg.
ACI CODE-440.11-22 strength reduction factors for reference: φ = 0.55 (tension-controlled) to 0.65 (compression-controlled) for moment and axial load, 0.75 for shear. Crack width, deflection, development length and bent-bar strength are checked in the member design.
F1 GFRP rebarStraight bars, factory-formed stirrups and mesh, with a bar schedule builder Send to engineeringGFRP reinforcement standards by market
| Market | Design | Bars | Notes |
|---|---|---|---|
| United States | ACI CODE-440.11-22 (buildings); AASHTO GFRP-2, 2nd ed. 2018 (bridges) | ASTM D7957/D7957M; ACI 440.11-22 references the 2022 edition | Construction: ACI SPEC-440.5-22. Test methods: ASTM D7205/D7205M |
| Canada | CSA S806:12 (R2021) (buildings); CSA S6:25 (bridges) | CSA S807:19 (R2024), grades by modulus and durability class | Provincial owners add their own requirements, e.g. Ontario OPSS |
| European Union | EN 1992-1-1:2023 Annex R (informative, FRP reinforcement), where adopted nationally | No harmonised product standard; CE marking through an ETA to EAD 260023-00-0301 | Test methods: ISO 10406-1:2025 |
| United Kingdom | No UK design standard of its own; the engineer adopts a recognised code, for example EN 1992-1-1:2023 Annex R, ACI CODE-440.11-22 or CSA S806 | Client specification; ETA or third-party certification | Test methods: ISO 10406-1:2025 |
| Australia | No national design standard; state road authority specifications, e.g. Queensland TMR MRTS271 (design to CSA S806) | AS 5204:2023 fibre-reinforced polymer bars | MRTS271 calls for CSA S807 Grade III bars |
| New Zealand | No local design standard; the engineer adopts ACI 440.11, CSA S806 or AS 5204 with the consent authority | Project specification, which can name AS 5204:2023 or CSA S807 | Confirm acceptance with the building consent authority |
Bar size cross-reference
Nominal diameters and areas of the steel bar series, with the closest GFRP diameter on the F1 inquiry list. ASTM D7957 GFRP bars use the ASTM A615 designations.
| Size | Ø mm | Area mm² | GFRP Ø |
|---|---|---|---|
| No. 2 | 6.4 | 32 | 6 |
| No. 3 | 9.5 | 71 | 10 |
| No. 4 | 12.7 | 129 | 12 |
| No. 5 | 15.9 | 199 | 16 |
| No. 6 | 19.1 | 284 | 20 |
| No. 7 | 22.2 | 387 | 22 |
| No. 8 | 25.4 | 510 | 25 |
| No. 9 | 28.7 | 645 | 28 |
| No. 10 | 32.3 | 819 | 32 |
| Size | Ø mm | Area mm² | GFRP Ø |
|---|---|---|---|
| Ø8 | 8 | 50 | 8 |
| Ø10 | 10 | 79 | 10 |
| Ø12 | 12 | 113 | 12 |
| Ø14 | 14 | 154 | 14 |
| Ø16 | 16 | 201 | 16 |
| Ø20 | 20 | 314 | 20 |
| Ø25 | 25 | 491 | 25 |
| Ø28 | 28 | 616 | 28 |
| Ø32 | 32 | 804 | 32 |
| Size | Ø mm | Area mm² | GFRP Ø |
|---|---|---|---|
| N10 | 10 | 79 | 10 |
| N12 | 12 | 113 | 12 |
| N16 | 16 | 201 | 16 |
| N20 | 20 | 314 | 20 |
| N24 | 24 | 452 | 25 |
| N28 | 28 | 616 | 28 |
| N32 | 32 | 804 | 32 |
| N36 | 36 | 1020 | 36 |
| Size | Ø mm | Area mm² | GFRP Ø |
|---|---|---|---|
| 10M | 11.3 | 100 | 12 |
| 15M | 16 | 200 | 16 |
| 20M | 19.5 | 300 | 20 |
| 25M | 25.2 | 500 | 25 |
| 30M | 29.9 | 700 | 30 |
| 35M | 35.7 | 1000 | 36 |
Specification practice is covered in the GFRP rebar specification guide, and the bar forms and schedule builder are on the FRP rebar page.
Frequently Asked Questions
Can I replace a steel bar with the same size of GFRP bar?
Not as a design decision. The size match helps you read a drawing and prepare an inquiry, but GFRP has roughly a quarter of the stiffness of steel, no yield plateau and its own bond, development and bend rules. The engineer of record redesigns the reinforcement to ACI CODE-440.11-22, CSA S806 or the code adopted for the project.
How does ACI CODE-440.11-22 reduce the bar strength?
The design tensile strength is the guaranteed tensile strength multiplied by the environmental factor C_E = 0.85. Under sustained load the bar stress is limited to 0.30 of that design strength to guard against creep rupture. The tool applies both to the certificate values you enter.
Which edition of ASTM D7957 applies?
The one named in the project specification. ACI CODE-440.11-22 was written around ASTM D7957/D7957M-22, while ASTM has since published later editions. Qualification reports should state the edition they were run against.
Which standards apply outside the United States?
Canada uses CSA S807 for the bars and CSA S806 or CSA S6 for design. Australia has AS 5204:2023 for FRP bars, and state road authorities such as Queensland TMR publish their own specifications. In Europe, bars are CE marked through a European Technical Assessment, and EN 1992-1-1:2023 has an informative annex on FRP reinforcement. The table on this page lists them by market.