A rebar bending chart tells you the smallest diameter a bar can be bent around without damaging it. For Canadian Grade 400W and 500W bar, the minimum finished bend diameter for standard hooks is 60 mm for 10M, 90 mm for 15M, 100 mm for 20M and 150 mm for 25M, rising to 550 mm for 55M. R grades need slightly larger bends, and stirrups and ties are allowed to bend tighter, at four bar diameters.
These values come from CSA A23.1 (Table 16 in the 2019 edition) and are reproduced in the Reinforcing Steel Institute of Canada (RSIC) Manual of Standard Practice, Fifth Canadian Edition (2020), which Canadian rebar shops bend to. The full chart, the stirrup values and the coated-bar values are below.
The rebar bending chart for main bars
This is the chart for standard hooks and bends on main bars (bars that are not stirrups or ties). D is the finished bend diameter, measured on the inside of the bar. The inside radius is half of D.
| Bar size | Bar diameter | 400R or 500R: D | Inside radius | 400W or 500W: D | Inside radius |
|---|---|---|---|---|---|
| 10M | 11.3 mm | 70 mm | 35 mm | 60 mm | 30 mm |
| 15M | 16.0 mm | 100 mm | 50 mm | 90 mm | 45 mm |
| 20M | 19.5 mm | 120 mm | 60 mm | 100 mm | 50 mm |
| 25M | 25.2 mm | 150 mm | 75 mm | 150 mm | 75 mm |
| 30M | 29.9 mm | 250 mm | 125 mm | 200 mm | 100 mm |
| 35M | 35.7 mm | 300 mm | 150 mm | 250 mm | 125 mm |
| 45M | 43.7 mm | 450 mm | 225 mm | 400 mm | 200 mm |
| 55M | 56.4 mm | 600 mm | 300 mm | 550 mm | 275 mm |
Three notes travel with this table:
- The 10% rule. Bend diameters may not be reduced by more than 10% from the listed values unless the owner's representative (in practice, the engineer) permits it.
- Large R-grade bars. For 45M and 55M bars in 400R or 500R, bends of more than 90° need special fabrication.
- Why W grades bend tighter. W-grade bar stretches further and is bend-tested around a tighter pin, so the hook tables allow a smaller diameter. Our post on 400W vs 500W rebar grades explains the grades.
As a rule of thumb, the minimum bend diameter for weldable bar works out to roughly five to six bar diameters for 10M to 25M, about seven for 30M and 35M, and close to ten for 45M and 55M. That is why heavy bars need so much more room at a corner.
Stirrups and ties bend tighter
Stirrups and ties wrap around main bars, so they use their own, smaller bend. CSA A23.1 sets the inside diameter of bends and 90° hooks on stirrups and ties at no less than four bar diameters. The RSIC stirrup and tie table puts that into pin sizes:
| Bar size | Pin diameter | Inside radius |
|---|---|---|
| 10M | 45 mm | about 23 mm |
| 15M | 65 mm | about 33 mm |
| 20M and larger | Same as main bar bends above |
Two refinements. In the 2004 edition of A23.1 (the edition we could check clause by clause), a 135° tie hook also had to be no tighter than 20 mm or the diameter of the bar it wraps around, whichever is greater. And stirrups and ties of 20M and larger go back to the main bar bend diameters. Hook lengths for stirrups are in our guide to stirrup sizes and hook lengths.
Pin diameter, bend diameter and bend radius
Searches for "rebar bending pin diameter", "bend diameter" and "bend radius" are often asking the same question, but the three are not the same number.
- Pin diameter is the size of the mandrel the bar is bent around on the bending machine.
- Finished bend diameter (D) is the inside diameter of the bend after the bar comes off the machine. Bars spring back a little, so the finished diameter is slightly larger than the pin. The chart above gives finished diameters. RSIC notes that where a hook has to be held to a restricted J dimension, the shop uses a pin smaller than the standard bend diameter to get there.
- Bend radius is half the bend diameter, measured to the inside of the bar. The centreline radius is larger by half a bar diameter. For a 20M 400W bar, the inside radius is 50 mm and the centreline radius is about 60 mm.
Detailers use these numbers to work out hook allowances and cut lengths. If you want the hook lengths that come out of the chart, see rebar hook length and bend radius.
Epoxy-coated and galvanized bar
Coatings need gentler bends, so they have their own charts. RSIC lists these minimum finished bend diameters:
| Bar size | Epoxy-coated: D | Galvanized: D |
|---|---|---|
| 10M | 80 mm | 60 mm |
| 15M | 120 mm | 90 mm |
| 20M | 160 mm | 120 mm |
| 25M | 200 mm | 200 mm |
| 30M | 250 mm | 240 mm |
| 35M | 350 mm | 280 mm |
| 45M | 450 mm | 450 mm |
| 55M | 600 mm | 550 mm |
The galvanized values come from ASTM A767, which sets the minimum bend at six bar diameters for 10M to 20M, eight for 25M to 35M and ten for 45M and 55M. Galvanized bar to A767 is normally bent before it is galvanized, so the bar list has to be final first. See galvanized vs epoxy-coated rebar for how the two coatings compare.
GFRP bar does not appear on this chart at all. It cannot be bent once it has cured, so bends are made by the manufacturer. Our post on GFRP corners, L-bars and hooks covers how those are ordered.
Metric chart vs the CRSI rebar bending chart
Many charts online, including the one in the Concrete Reinforcing Steel Institute (CRSI) manual, are American. They follow ACI 318, which states minimum bend diameters as multiples of bar diameter: six bar diameters for #3 to #8, eight for #9 to #11 and ten for #14 and #18.
The logic is similar to the Canadian chart, but you cannot read one off the other:
- Bar sizes differ. A #5 bar is 15.9 mm and a 15M bar is 16.0 mm, but #6 and 20M, #8 and 25M and the larger sizes do not line up. See Canadian vs US rebar sizes.
- The tables are built differently. CSA A23.1 lists millimetre values by grade, R or W. ACI uses one multiple of bar diameter regardless of grade.
- Hook lengths differ because the extensions and bend diameters differ.
If you are working from American drawings on a Canadian job, have the bar list detailed in metric sizes to the Canadian tables. Our comparison of ACI and CSA rebar detailing goes through the other differences.
Radius bending and very large bends
The chart covers hooks and tight bends. Large curves are a separate category. RSIC treats bends with an inside radius of 300 mm or more as radius bending, shown on bar lists as Type 9 or Type 10. The shop radius-bends a bar when the curve is tighter than the RSIC table for that bar size. Bars with a larger radius than that are shipped straight and sprung into place in the field, because they will follow the formwork without permanent bending.
A few other limits are worth knowing before you finalize a detail:
- Bending in more than one plane is possible but costs more, and it is often simpler to use two bars lapped together.
- Field bending of bars already partly cast into concrete is not allowed unless the drawings show it or the engineer permits it. Our post on whether bending rebar weakens it covers field bending, heating and rebending.
- Offset (cranked) column bars have their own geometry limits in CSA A23.3, covered in our guide to standard rebar hooks and bends.
Using the chart on your project
The chart is a minimum, not a target. Your structural drawings and the bar list control what gets bent, and the shop bends to the RSIC pin sizes that meet these minimums. Before sign-off, check three things: the grade on the drawings (it changes the bend diameter), whether any bars are coated, and whether any corner or hook is too tight for the bar size shown.
Procut bends 10M to 55M bar to all standard shapes in our Erin shop, tagged and bundled by mark. Send us your drawings or bar list for a free take-off and quote, or see our rebar products for straight, fabricated and GFRP bar.
Frequently asked questions
What is the minimum bend diameter for 15M rebar?
For standard hooks and bends on Grade 400W or 500W bar, the minimum finished bend diameter for 15M is 90 mm. For 400R or 500R bar it is 100 mm. Stirrups and ties of 15M are bent tighter, around a 65 mm pin.
What is the bending radius of 10M rebar?
The minimum inside bend diameter for 10M is 60 mm for weldable (W) grades and 70 mm for R grades, so the inside radius is 30 mm or 35 mm. 10M stirrups and ties are bent around a 45 mm pin, an inside radius of about 23 mm.
Is the bend diameter measured to the inside of the bar?
Yes. CSA A23.1 measures the bend diameter on the inside of the bar. The radius to the centre of the bar is larger by half a bar diameter, which matters when you calculate bar lengths.
Can I use a CRSI rebar bending chart in Canada?
Not for Canadian metric bar. CRSI charts follow ACI 318 and use inch-pound bar sizes (#3, #4 and so on). Canadian bars are bent to the CSA A23.1 values for 10M to 55M, which are published in the RSIC Manual of Standard Practice.
Is there a rebar bend chart PDF?
The official tables are in CSA A23.1 and the RSIC Manual of Standard Practice, both sold by their publishers. The chart in this post reproduces the minimum bend diameters from those sources, so you can print it, but check it against the edition named on your drawings.
