A bar is formed around a pin or mandrel on bending equipment, but the nominal pin diameter, the specified minimum finished bend diameter and the curvature you measure on the finished bar are not always the same thing. Bars also spring back slightly after bending.

CRSI recommends two checks: the inside bend diameters specified and fabricated should be equal to or larger than the applicable ACI minimum, and the pins used for fabrication should be equal to or larger than the pin diameters required by the applicable ASTM specification. ASTM bend-test pin diameters, ACI minimum bend diameters and CRSI finished bend diameters are three different values, so confirm which one a drawing or fabricator means.

CRSI describes inspecting finished bends with a disc-style template sized to match the required minimum bend diameter. The result is read this way:

• If the disc fits inside the bend, the bar was bent to at least the required diameter.
• If the disc does not fit, the bend was fabricated with a diameter smaller than the specified ACI minimum.
• If the disc fits but a small gap shows, the gap is most likely a small curvature variance. As long as the finished diameter is equal to or larger than the required minimum, the gap is not cause for rejection.

Finished bends are not perfect circles. CRSI lists causes such as pin and bar geometry, equipment wear and setup, bar type, the rib position against the pin, variance in deformation height, and permissible angular deviation. Gap limits are set in CRSI’s current standard (ANSI/CRSI IPG5.1-2026), so use that document for acceptance tolerances.

• The reinforcing steel: a bend that is too tight can damage or overstrain the bar during bending.
• The concrete inside the bend: a very tight curve concentrates bearing force on the concrete wrapped around the bar, raising the risk of local crushing.

The ACI multipliers exist to keep both effects in check. This page gives the multipliers, not stress limits; the design basis belongs to the engineer of record.

Follow the adopted ACI edition, the construction documents, the bar material and grade, the fabrication standard and the licensed design professional. A tighter shop bend can require special fabrication even where a structural-code minimum permits it. CRSI documented this for small stirrups and ties: bending Grade 60 stirrups and ties to 4db is a special-order item that should be clearly noted on the construction documents.

Do not heat rebar to bend or straighten it unless an approved procedure authorizes it; this page gives no heating procedure. Rebending a bar that has already been bent can affect steel ductility, bar integrity, coatings and geometry. It needs project-specific approval and the engineer’s direction under applicable CRSI and ACI guidance.

High-Strength Bars

CRSI lists commonly used reinforcing specifications including ASTM A615, A706, A955, A996 and A1035. Do not assume every grade and material can be shop-bent identically because the nominal diameter matches. ASTM A615-20 increased the bend-test pin diameter to 5db for grades above 75, and CRSI’s fabrication guidance ties finished bends to both ACI and ASTM requirements.

Epoxy-Coated Bars

Coating systems add fabrication considerations. CRSI maintains a separate standard for epoxy-coated reinforcing bar fabrication facilities (CRSI CG2.1-2026). Do not copy uncoated bend values onto coated bars without checking the project specification.

Galvanized Bars

Galvanized bars can have different finished bend requirements. The CRSI 29th Edition Table 7-4 (ASTM A767) lists #7 and #8 galvanized finished bend diameters at 8db (7.00 and 8.00 in.), larger than the 6db used for uncoated bars of those sizes. Check the current edition and project specification.

A larger bend consumes space. The outside radius, the minimum concrete cover, the member dimensions and adjacent bars must all fit together. A minimum bend radius never overrides required cover. You can check cover quickly with the rebar cover calculator.

Large bends can also affect clear spacing, congestion, hook placement and the geometry at beam-column joints and footing corners. See the rebar spacing requirements and the rebar spacing calculator for spacing limits.

Keep them apart: the rebar hook length chart owns the extensions, and rebar development length is a structural anchorage quantity that is never equal to hook radius or hook extension.

Because a bend has a radius, the length of steel in the bend is shorter than the sum of the outside leg dimensions. CRSI fabrication standards use defined measuring points for bent bars, and ANSI/CRSI IPG5.1-2026 covers bend diameters, measuring points and fabrication tolerances. In CRSI’s detailing practice, most dimensions are out-to-out of the bar, with a few exceptions on standard 180-degree and 135-degree hooks.

For stock lengths, cut lengths and bar schedules, use the rebar length chart. This page only explains how curvature affects the geometry.

Standards and References Used

Local adopted codes, the edition of ACI 318 in force, project specifications, the engineer of record and the fabricator can change the requirement for a given job. Older CRSI edition values are shown only as published references.