Log Cabin Calculator
Zero Waste & No Sign-up: Calculate strip widths and lengths for Log Cabin quilt blocks. Enter finished block size and strip width to get precise cutting measurements for every round.
How to Use the Log Cabin Calculator
Enter the finished center square size, the finished strip (log) width, the number of rounds, and your seam allowance. The calculator produces a complete cutting list: the center square plus the exact length of every log in every round.
All strips are cut at the finished log width plus two seam allowances. Within each round, the log lengths step up — the first log matches the block as it stood before the round, the middle logs add one strip width, and the last matches the block after the round — each with seam allowances added. The block grows by twice the strip width per round.
The tool also reports the final block size: center plus two times rounds times strip width. A 2-inch center with 1-1/2 inch logs grows to 11 inches finished after three rounds, cut size 11-1/2 inches. Verify your block against this number after each round and you will catch a wandering seam allowance long before quilt top assembly.
Frequently Asked Questions
How big will my log cabin block finish?
The final size is the center plus twice the rounds times the strip width. A 2-inch center with 1-1/2 inch finished logs reaches 5 inches after one round, 8 inches after two, and 11 inches after three.
What width should I cut log cabin strips?
Cut strips at the finished log width plus two seam allowances — 2-inch strips for 1-1/2 inch finished logs at a quarter-inch seam. The calculator lists the exact length of every log so each round is cut to size instead of trimmed as you go.
Why are the logs in one round different lengths?
Each log is sewn to a block that has grown since the previous log. Within a round the first log matches the incoming block edge, the two middle logs run one strip width longer, and the last matches the block as it leaves the round — each plus seam allowances.