How much bigger should a bowl blank be than the finished bowl?

Allow at least 10mm extra on the diameter (5mm each side) for truing up the blank on the lathe. For depth, add 10-15mm for the mounting tenon or waste block. For green (wet) wood, add an extra 10% to allow for shrinkage as the bowl dries.

What is a good wall thickness for a turned bowl?

For dry-turned bowls, 6-10mm is typical for decorative pieces, 8-12mm for functional bowls. For green-turned bowls that will distort as they dry, turn to 10% of the diameter (e.g., 25mm walls for a 250mm bowl) and re-turn after drying.

What speed should I turn a bowl blank at?

For roughing out, start slowly: approximately 6,000-9,000 divided by the blank diameter in inches gives the maximum RPM. A 200mm (8 inch) blank should start at around 1,000 RPM maximum. Increase speed as the blank becomes more balanced and round.

What size faceplate should I use?

The faceplate diameter should be roughly one-third of the bowl diameter. For a 200mm bowl, use a 60-75mm faceplate. The faceplate must be fully supported by solid wood - never let screws go into the part of the blank that will become the bowl interior.

WoodCalcs

Bowl Blank Calculator — Blank Dimensions for Turned Bowls

Calculate bowl blank dimensions and wood required for turned bowls.

Wood Species

Finished Bowl Diameter

Diameter of the circular area

Finished Bowl Depth

Thickness or depth of the material

Wall Thickness

Material thickness

How We Calculate This

This calculator determines the minimum blank dimensions needed to turn a bowl to your specified finished size.

Blank sizing

Blank diameter = Finished diameter + 20mm (10mm each side for truing)

Blank thickness = Finished depth + 15mm (for tenon and mounting waste)

Safe speed

Max RPM = 8,000 / Diameter in inches (rough guideline for initial roughing)

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify measurements and material quantities before cutting or purchasing.