Choosing the right portable rebar bender size starts with one question: what is the largest bar you need to bend? For common U.S. reinforcing bar sizes, the practical matches are straightforward: use the NRB-16 for #5 rebar, NRB-20 for #6, NRB-25 for #8, and NRB-32 for #10. However, diameter is only the first part of the selection process. Steel grade, tensile strength, bend angle, bend radius, and duty cycle can all affect real-world capacity.
Quick Answer: #5, #6, #8 and #10 Rebar Bender Sizes
| U.S. Rebar Size | Nominal Diameter | Approx. Metric Diameter | Recommended POWER Model | Rated Maximum Diameter |
|---|---|---|---|---|
| #5 | 0.625 in | 15.9 mm | NRB-16 portable rebar bender | 16 mm |
| #6 | 0.750 in | 19.1 mm | NRB-20 portable rebar bender | 20 mm |
| #8 | 1.000 in | 25.4 mm | NRB-25 portable rebar bender | 25 mm |
| #10 | 1.270 in | 32.3 mm | NRB-32 portable rebar bender | 32 mm |
This table is a fast selection guide, not permission to exceed a machine rating. The correct model is the one whose approved capacity covers the actual diameter and strength of your rebar under the required bending conditions.
What Does a Rebar Size Number Mean?
For the common U.S. bar-number system, the number is approximately the nominal diameter in eighths of an inch. Thus, #5 is about 5/8 inch, #6 is 6/8 or 3/4 inch, and #8 is 1 inch. #10 is a larger bar with a nominal diameter of about 1.27 inches. The Concrete Reinforcing Steel Institute terminology guide explains this bar-number convention and its metric equivalents.
Portable bender model names normally state a rounded maximum metric diameter. That is why a nominal 15.875 mm #5 bar is paired with a 16 mm bender and a nominal 19.05 mm #6 bar is paired with a 20 mm model. The #8 and #10 conversions sit very close to 25 mm and 32 mm ratings, so checking the precise bar certificate becomes especially important.
#5 Rebar: Choose the NRB-16
#5 rebar has a nominal diameter of 0.625 inch, or about 15.9 mm. The NRB-16 is the natural portable choice for this size because its maximum bar diameter is 16 mm. It is well suited to contractors who regularly fabricate stirrups, hooks, anchors, landscaping reinforcement, and small-to-medium structural components on site.
If most of your work is #4 and #5 rebar, the NRB-16 keeps the tool compact without buying more capacity than the job requires. Before production, make a test bend using the same bar grade and diameter as the project material.
#6 Rebar: Choose the NRB-20
#6 rebar measures 0.750 inch, or approximately 19.1 mm. The NRB-20 provides a 20 mm rated diameter and is the appropriate step up from the NRB-16. It gives contractors enough capacity for common #6 work while remaining easier to move between work zones than a stationary bending machine.
The extra capacity should not be treated as an invitation to bend multiple bars at once. Unless the product specification expressly allows multi-bar bending, feed one bar at a time and keep the workpiece properly supported.
#8 Rebar: Choose the NRB-25
#8 rebar has a nominal diameter of exactly 1.000 inch, or 25.4 mm. In common tool selection, the NRB-25 is the corresponding model. Because the imperial-to-metric conversion is slightly above 25 mm, verify the model specification, bar grade, and manufacturer tolerances before committing to a large batch.
This model is typically considered for foundations, retaining structures, commercial building reinforcement, and other jobs where larger bars must be bent close to the installation area. For demanding material or sustained production, discuss your exact bar specification and duty cycle with the supplier.
#10 Rebar: Choose the NRB-32
#10 rebar is a heavy bar with a nominal diameter of about 1.270 inches, or 32.3 mm. The NRB-32 is the largest model in this NRB portable range and is the correct starting point for #10 applications.
At this size, never rely on the bar number alone. Obtain the mill certificate or project material specification, confirm the steel grade, and check the required bend radius. Heavy rebar places much higher loads on the bending head, pins, rollers, and support surface. If the actual diameter, strength, or bend requirement lies outside the published limit, use a higher-capacity solution instead of forcing the tool.
What About Intermediate Sizes? NRB-22 and NRB-28
The POWER NRB lineup also includes two useful intermediate options. The NRB-22 portable rebar bender fills the gap between 20 mm and 25 mm work, while the NRB-28 portable rebar bender sits between the 25 mm and 32 mm models. They are especially relevant when projects are specified in metric bar diameters or when your regular bar mix includes sizes near #7 or #9.
Using the smallest model that safely covers your material usually improves portability. Choosing the next larger model can make sense when future work will include a wider diameter range, but capacity should be selected from verified job requirements rather than guesswork. See the complete rebar bender range for a broader comparison.
Why Diameter Alone Is Not Enough
- Steel grade and strength: two bars with the same diameter may require different bending forces. Standards such as ASTM A615/A615M cover deformed and plain carbon-steel bars in multiple grades.
- Bend angle and radius: a tight bend or large angle can create a more demanding load than a gentle bend.
- Bar condition: damaged, heavily corroded, coated, cold, or previously bent material may behave differently.
- Duty cycle: occasional site adjustments and continuous fabrication are different workloads. Allow cooling and maintenance intervals specified by the manufacturer.
- Power supply and setup: voltage, extension-cord size, stable footing, and correct pins or rollers affect safe operation.
In short, a portable rebar bender size rating is a maximum under defined conditions, not a universal guarantee for every bar of that nominal diameter.
How to Choose the Right NRB Model
- Identify every bar size on the project. Select for the largest diameter you will actually bend.
- Confirm the standard and grade. Read the project specification or mill certificate rather than judging the bar by appearance.
- Check the required geometry. Confirm bend angle, bend radius, hook type, and clearance at the work area.
- Match the material to the published machine rating. Keep the actual bar within the approved diameter and strength limits.
- Consider frequency and mobility. Choose a portable model for field movement and localized bending; consider a production machine for high-volume repetitive fabrication.
- Test before the production run. Inspect the first bend for angle, radius, cracking, and tool stability.
Portable Rebar Bender Safety Checklist
- Read the model manual and inspect the bender, cord, hydraulic components, pins, and rollers before use.
- Wear suitable eye, hand, foot, and hearing protection for the jobsite.
- Keep hands away from the bending head and the bar’s swing path.
- Support long bars so they do not whip, fall, or strike nearby workers.
- Disconnect power before changing accessories, clearing a jam, or servicing the machine.
- Use guards, controls, and safe operating practices consistent with OSHA’s general requirements for power tools.
Frequently Asked Questions
Can a 16 mm portable rebar bender bend #5 rebar?
Yes. #5 rebar is nominally 15.875 mm, so the NRB-16 is the corresponding model. Confirm the bar grade and the tool’s detailed capacity before use.
Which portable bender should I use for #6 rebar?
Choose the NRB-20. #6 rebar is approximately 19.05 mm in diameter, which fits the 20 mm size class.
Can the NRB-25 bend #8 rebar?
The NRB-25 is the intended match in this selection guide. Since #8 is nominally 25.4 mm, verify the exact product limit and material specification before bending.
What is the best portable rebar bender for #10?
Start with the NRB-32, then confirm the actual diameter, grade, bend radius, and duty cycle. #10 is a demanding size, so never exceed the machine’s published conditions.
Can I bend more than one bar at the same time?
Do not bend multiple bars unless the manufacturer explicitly rates the machine for that operation. Combined cross-sectional area and uneven loading can overload the tool even when each individual bar appears small enough.
Final Model Recommendation
For the four sizes in this guide, the answer is: #5 → NRB-16, #6 → NRB-20, #8 → NRB-25, and #10 → NRB-32. Choose the portable rebar bender size that covers your largest verified bar without exceeding the machine’s diameter, grade, or operating limits.
If you are unsure which model fits your rebar standard, steel grade, bend angle, or project volume, contact POWER with the bar specification and required application. We can help you compare NRB-16, NRB-20, NRB-22, NRB-25, NRB-28, and NRB-32 before you order.