Circle Glue-Up Calculator
Building a round tabletop, lazy Susan or clock face? Enter the finished diameter and the width of your boards, and get the length to cut each board before glue-up — no more gluing a full square and throwing half of it away.
Board lengths for a circular glue-up, each cut long enough to cover the circle plus trim allowance all around. Rounds up to the nearest 1/4 in. Thanks to Shawn @LonesomeRoadWoodworks for this one.
Round top sorted. Now the rest of the build.
CUTLIST.io bundles all five shop calculators with the cut list optimizer — Rip First, Crosscut First, Max Yield, or Smart Stack — so you buy the right amount of material and waste less of it.
Get the whole suite of toolsHow a round glue-up is laid out
Stack boards edge to edge, centered on the circle. The boards near the middle have to span almost the full diameter; the ones at the top and bottom only cross a short chord. Cutting each one to the length it actually needs saves a lot of wood on a big top.
where R = radius + trim allowance, y = the board edge nearest the center
Trim allowance is added around the whole circle, not just to the ends of each board, so after glue-up you have consistent material everywhere to true the circle with a router trammel, bandsaw and sander, or a circle-cutting jig. Lengths round up to your chosen step so you can cut to a tape mark.
Equal width compensation
The two outermost boards straddle the edge of the circle, so part of their width gets cut away. Left alone, they finish narrower than the rest. With compensation on, every board is ripped to the one width that divides the diameter evenly, and the two end boards get the trim allowance added back — so every row finishes the same width once the circle is cut.
More free shop calculators
Board Foot Calculator
Board feet and lumber cost for a list of boards.
Tape Measure Calculator
Add, subtract, multiply and divide tape measurements, fractions included.
Woodworking Unit Converter
Inches, mm, cm, feet — with fractions in and out.
Quick Fill Calculator
How many of one part fit on a sheet, kerf included.
Questions
What trim allowance should I use?
1/2" is a good default for a router trammel or bandsaw-and-sand. Use more if your blank is likely to shift during glue-up or you plan to flatten after.
Which boards are which in the list?
Boards come in mirrored pairs (the top and bottom board are the same length), listed longest first — that's the center of the panel. A lone single board appears when the count is odd.
Does it account for grain or glue line position?
No — it's pure geometry. Arrange the boards for grain first, then cut them to these lengths.
Can I do this for the whole project?
The CUTLIST.io optimizer lays out every part in a build across your stock. This calculator handles the one thing a rectangular optimizer can't: a circle.