Sheet Metal Bend Allowance Calculator
Bend allowance and total flat length for a sheet metal part before folding.
Results
Bend allowance
6.0947
mm
Flat blank length
96.095
mm
Difference
3.9053
mm
What this tool does
Metal stretches on the outside of a bend and compresses on the inside, and somewhere between the two sits a line that does neither — the neutral axis. The K factor says where that line is, typically 0.33 to 0.45 depending on material and tooling, and it decides how much material the bend actually consumes.
Formula
BA = (π ÷ 180) × angle × (R + K × T)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
a | Bend angle | ° |
r | Inside bend radius | mm |
t | Thickness | mm |
k | K factor | — |
l1 | Length | mm |
l2 | Length | mm |
BA | Bend allowance | mm |
FL | Flat blank length | mm |
BD | Difference | mm |
Worked example
- Bend angle90 °
- Inside bend radius3 mm
- Thickness2 mm
- K factor0.44
- Length50 mm
- Length40 mm
- Bend allowance6.0947 mm
- Flat blank length96.095 mm
- Difference3.9053 mm
Limitations
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.