Bending Radius CalculatorWood Bending Radius & Method Calculator
Determine whether a wood curve is achievable. Calculate the minimum bend radius for steam, lamination, kerf and cold bending, with ply counts for lamination and springback allowance.
Why this calculation matters
Radius and lamination thickness decide whether the bend succeeds or the piece breaks. Halving thickness quarters the stress, which is usually cheaper than steaming harder.
Bending Radius Calculator
Wood Bending Radius & Method Calculator
Inside radius of the curve.
0 = auto. Only for kerf bending.
| Property | Value | Detail |
|---|
About Bending Radius Calculator
Wood can be curved by several methods, each with a different minimum achievable radius. This tool checks whether your desired radius is feasible for a given thickness and method, and for bent lamination it calculates the required ply thickness and count. It also estimates springback so you know how much to over-bend the form. It gives the minimum bend radius for wood before failure, useful alongside any steam bending guide when planning a curved part.
Where Is This Used?
Formulas & Rules
Minimum radius = ratio x thicknessBent lamination ~ 2x thickness | Steam ~ 10x | Plywood ~ 12xSolid cold bend ~ 50x thickness (very limited)Lamination ply thickness ~ radius / 50Kerf count = (arc length) / kerf spacingHow the calculation works
A thick piece cannot take a tight curve because the outer face has to stretch further than the fibres allow. Every method is a way around that: steam makes the fibres yield, lamination and kerfing replace one thick piece with several thin ones that each bend easily.
Show the formula
Minimum radius = thickness x the ratio for the method (solid, steamed, laminated or kerfed). Laminations = ceiling(thickness / ply thickness). Kerf cuts = ceiling(pi x radius / 2 / spacing) over a quarter arc. A springback allowance is added by method.The steam ratio of 16 times thickness is the USDA FPL figure for a 75% yield of near-perfect pieces; FPL achieved 12 times on optimum straight-grained, low-density stock, so treat anything tighter as a test piece. The lamination and kerf ratios have no published table — with those methods the real limit is set by how thin you can cut the plies or how much skin you leave, not by the original stock thickness. Springback is an allowance, not a prediction.
References and what each one provides
- USDA FPL — Steam-bending properties researchMeasured bending ratings against radius-to-thickness ratio. Found a radius of about 16 times thickness gave a 75% yield of near-perfect pieces, with 12 times achievable on optimum straight-grained, low-density stock.Measured radius-to-thickness ratios for steam bending.
- USDA Wood Handbook (FPL GTR-190)USDA Forest Products LaboratorySpecies bending classification and the grain properties that govern it.
Unverified values are marked as such rather than presented as sourced.
Limitations of this calculation
Assumes straight-grained, defect-free stock at suitable moisture content. It does not account for grain runout, knots, springback after release, species variation in plasticity, or the effect of steaming time and temperature.
Do not use this for Structural laminated members, or bent components carrying load.
Figures are engineering estimates from the inputs and assumptions shown. Verify against the actual material and, where the result affects structure or safety, against a qualified professional.
- Minimum radius = method radius-to-thickness ratio × thickness
Formula checked against the sources above by an automated regression test (tests/verify-phase2.js) that derives each expected value independently of this page. Last reviewed .
How to use this tool
- Enter your material and machine details below, then press Calculate.
- Pick your bending method from the dropdown.
- Fill in material thickness, desired bend radius, kerf spacing.
- Press Calculate.
Worked example
Common mistakes to avoid
- Trying to cold-bend kiln-dried wood to a tight radius. Dry wood snaps; steam or laminate instead.
- Ignoring grain direction. Wood with grain run-out breaks at a fraction of the expected radius.
- Bending to the target radius exactly. Wood springs back — over-bend slightly and let it settle.
Frequently Asked Questions
Wood species data
Density, hardness and movement for 60 timbers
Full listing in the thermal conductivity table.