Use the calculator to estimate a bend (centerline) radius from tube outside diameter (Quick 2×D), get an approximate minimum recommended centerline radius based on diameter, wall thickness, material, and bending method (Minimum CLR), or calculate bend arc length from centerline radius and bend angle (Bend Arc Length).
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Tube Bend Radius Formula
A common rule of thumb for a relatively gentle bend is to use a centerline radius about twice the tube outside diameter:
R \approx 2D
- Where R is an approximate bend centerline radius (CLR)
- D is the tube outside diameter (OD)
This 2×D relationship is not universal. The minimum achievable/recommended bend radius depends on factors such as material, wall thickness (D/t), tooling and bending method (mandrel vs. no mandrel), and acceptable ovality/thinning/wrinkling.
Definition
What is a tube bend radius?
A tube bend radius (often specified as the centerline radius, CLR) is the distance from the center of curvature of the bend to the centerline of the tube.
Choosing too small of a bend radius can reduce bend quality and may cause excessive ovality/flattening, wall thinning on the outside of the bend, or wrinkling/buckling on the inside. The bend angle does not determine the radius; it affects the arc length of the bend for a given radius.
Example Problem
How to calculate a bend radius?
The following example problem outlines the steps and information required for calculating a tube bend radius using the 2×D rule of thumb.
For this quick estimate, the only piece of information you need is the tube outside diameter (OD), not the inside diameter.
For this example problem, the outside diameter is 5 inches.
Next, simply use the formula above to estimate the bend radius:
R ≈ 2 × D
R ≈ 2 × 5
R ≈ 10 inches
