ABOUT THE TOOL
Simple math for your next blanket.
Blanket Math is a free calculator for planning rectangular crochet blankets. Use your own measurements to estimate working stitches, rows and yarn. There is no account to create.
How the calculations work
Stitch gauge = counted stitches ÷ measured width. Row gauge = counted rows ÷ measured height. Multiply these by the target blanket width and length to get the unrounded counts.
For a working-stitch repeat of M plus E edge stitches, the result is M × N + E, where N is the closest whole number of repeats, with a minimum of one. When two counts are equally close, the larger is selected. Rows round to the nearest whole row, with a minimum of one. The estimated dimensions use these rounded counts divided by your gauge.
Starting chains are calculated only when you enter a known rule: working stitches plus extra foundation chains. The calculator does not infer this from a stitch name or translate a foundation-chain repeat into a working-stitch repeat.
Optional yarn estimates use the area of the entire weighed sample: sample grams ÷ sample area × calculated blanket area × (1 + allowance ÷ 100). Divide by the weight of one skein of the same yarn, then round up to whole skeins. The display rounds estimated grams upward.
A worked example
With 16 stitches and 12 rows measured over 4 × 4 inches, a 50 × 60 inch blanket needs 200 working stitches and 180 rows. If a separate full 4 × 4 inch sample weighs 8 grams, the same fabric would require approximately 1,500 grams before any allowance, or 1,650 grams with 10% extra: 17 skeins of 100 grams each.
What this tool does not do
It does not generate a crochet pattern, adjust shaping or row repeats, predict borders, or calculate corner-to-corner blankets or granny squares. Yarn estimates assume the same stitch, yarn, hook and tension throughout. Sample measurements, finishing and tension changes affect the result. The blanket size presets are suggestions, not universal standards.
Check the results against your pattern and a representative swatch before committing to a project.