Block Layout Calculator

Because a whole number of blocks has to fit in each direction — the calculator can't cut a fractional block to hit your exact target. It rounds to the nearest whole block count across and down, then reports the real finished width and length that whole-block count produces. Width Difference and Length Difference show you exactly how far that lands from your original target, so you can decide whether the drift is acceptable.

Sashing adds to the effective footprint of every block, since each block-plus-seam unit takes up its finished size plus one sashing strip. A wider sashing means fewer blocks fit across the same target width or length, which is why increasing Sashing Width can reduce Blocks Across and Blocks Down even though the block size itself hasn't changed. Set Sashing Width to 0 if your quilt uses edge-to-edge blocks with no sashing at all.

No. Blocks Across is calculated purely from Target Quilt Width, Finished Block Size, and Sashing Width, while Blocks Down is calculated purely from Target Quilt Length using the same block size and sashing. Changing the length target has no effect on how many blocks fit across, and vice versa — the two dimensions are computed independently.

Try a slightly different Finished Block Size or Sashing Width and recalculate — even a small change shifts which whole-block count is closest to your target, which can substantially reduce the drift. Alternatively, some quilters accept the calculated size and adjust the border width instead, since a wider or narrower border can absorb a few inches of difference without altering the block grid itself.