Lumbertool Calculate board feet

Round tabletop glue-up cut lengths

Prepare equal-width boards for a circular tabletop and trim each board to the chord that covers the circle at its nearest-to-centre edge.

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Example inputs · U.S. customary units

A 24 in round top from 6 in strips. This example has no radial trim. Enter the allowance and usable board width for your blank.

Example: 24 in.

Example: 0 in.

Example: 6 in.

Results

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Enter your values, then choose Calculate. Your results will appear here.

How to use round tabletop glue-up cut lengths

What this calculation does

This layout estimates equal-width strips for a centered circular tabletop and the straight blank length each strip needs before the circle is cut.

Enter the finished diameter, radial trim allowance and measured usable width of the boards used in the glue-up.

Enter the measurements

  1. Finished tabletop diameter: Measure the finished circle across its widest point.
  2. Radial trim allowance around the circle: Add the planned trim beyond the finished radius.
  3. Measured usable board width: Measure each board after edge preparation.

Formula and variables

Glue-up radius = finished diameter ÷ 2 + radial trim. Board count = ceil(finished diameter ÷ usable board width). For each centered board strip, let y be the strip edge nearest the circle centre; required cut length = 2 × sqrt(radius² − y²).

The circle radius is half the diameter plus radial trim. Each strip length is a chord based on the strip edge nearest the circle center.

Read the result

Four boards span the 24 in circle. The two center strips need 24 in blanks and the outer strips need about 20.785 in each.

Worked example

Inputs: 24 in finished diameter, zero radial trim and 6 in usable boards

  1. Radius = 24÷2 + 0 = 12 in; board count = ceil(24÷6) = 4.
  2. An outer chord is 2√(12²−6²) ≈ 20.785 in; total length is (20.785+24+24+20.785)÷12 ≈ 7.464 ft.

Expected result: 4 boards: about 20.785, 24, 24 and 20.785 in; 7.464 ft total

Frequently asked questions

Are these finished curved edges?

No. They are straight rectangular blank lengths before the circle is laid out and cut.

Does the board count include a width allowance?

Only the entered radial trim changes the circle radius; defects and strip-width optimization are not included.

Conditions, presets and technical notes

Assumes equal-width boards laid edge-to-edge and centered across the circle. Radial trim is added around the full circle. The lengths are straight rectangular blanks before the circular edge is cut. Grain, defects and strip-width optimization are excluded.