Block Resizer Calculator

Why resizing blocks by hand goes wrong

The intuition is to multiply everything by the same scale factor. A 6" block becomes 9", so just multiply each cut size by 1.5, right? Wrong. Seam allowances don't scale — they're always 1/4" regardless of block size. If you scale the full cut dimension, you end up with oversized seam allowances that throw off every measurement in the block.

The correct process: strip the seam allowance from the original cut size to get the finished dimension, scale that, then re-add the seam allowance. And the seam allowance formula varies by piece type — an HST adds 7/8", a QST adds 1 1/4", a square adds 1/2". For a block with 8 different piece types, that's a lot of math to get right by hand.

The Block Resizer handles all of this automatically. Enter your original block size and target size, define your pieces (or upload a photo to auto-detect them), and get exact cut dimensions with the correct seam allowances for every piece type. It supports HSTs, QSTs, flying geese, half-rectangle triangles, squares, rectangles, strips, and more.