Calculator Inputs
Recent Calculation History
Formula Used
Arc length: L = (θ ÷ 360) × 2πR. The same expression can be written as L = θ × π ÷ 180 × R.
Tube radii: inside radius equals centerline radius minus half the diameter. Outside radius equals centerline radius plus half the diameter.
Sheet-metal allowance: BA = θ × π ÷ 180 × (R + K × T). Bend deduction equals twice the setback minus bend allowance.
Minimum flexible-product radius: Rmin = outside diameter × selected multiplier. Always replace generic multipliers with manufacturer limits when available.
How to Use This Calculator
- Select the mode matching your pipe, cable, hose, conduit, or sheet-metal task.
- Choose input and output units before entering dimensions.
- Select a material preset, then adjust its editable values.
- Enter the bend angle, radius, diameter, thickness, and straight lengths.
- Add springback, tooling, mandrel, or K-factor details when known.
- Press Calculate Bend and review warnings before fabrication.
- Copy, print, or export results for project records.
Understanding Bend Radius
Bend radius describes the curvature of a formed component. The measurement may reference the inside surface, centerline, or outside surface.
A larger radius usually lowers strain and distortion. A smaller radius creates tighter geometry but may increase cracking, flattening, wall thinning, or signal damage.
Manufacturer limits, material condition, tooling, temperature, and service motion can change acceptable values. Treat calculator warnings as screening guidance rather than certification.
Example Calculations
| Application | Inputs | Formula | Example Result |
|---|---|---|---|
| Tube bend | 25 mm OD, 75 mm CLR, 90° | L = πR/2 | 117.810 mm arc |
| Cable | 12 mm diameter, 6× multiplier | Rmin = 6D | 72 mm minimum radius |
| Sheet metal | 2 mm thick, 3 mm radius, K 0.33, 90° | BA = π/2 × (R + KT) | 5.749 mm allowance |
| Offset | 50 mm offset, 30° angle | Spacing = offset/sin angle | 100 mm mark spacing |
Frequently Asked Questions
What is centerline bend radius?
It is the radius measured to the center of the pipe, tube, cable, or formed section.
How is inside radius different?
Inside radius is measured to the inner surface. For round tube, subtract half the outside diameter from centerline radius.
What does a 3D bend mean?
A 3D bend normally has a centerline radius equal to three outside diameters.
Can one multiplier fit every cable?
No. Cable construction, loading state, installation method, and manufacturer rules can require different multipliers.
What is bend allowance?
Bend allowance is the neutral-axis arc length included in a sheet-metal flat pattern.
What is bend deduction?
Bend deduction is removed from outside leg totals to determine the required flat length.
Why is K-factor editable?
Material, tooling, radius, and forming method change the neutral-axis position.
Does springback change the arc length?
This calculator can add springback to the forming angle. Actual compensation should come from trials or validated process data.
When is a mandrel useful?
Mandrels can reduce collapse, wrinkling, and ovality during tight tube bends.
Are strain and ovality values exact?
No. They are preliminary estimates and cannot replace process simulation, testing, or inspection.
Should results replace manufacturer limits?
No. Manufacturer data, applicable codes, and qualified fabrication procedures always take priority.