This calculator computes only the blanket-to-swatch area ratio; it does not estimate yarn mass or skein count. Use the formula and worked examples below for manual yarn calculations. Whole-skein counts must be rounded upward; decimal display rounding is not a substitute.
Use the blanket’s yarn, stitch pattern, needle or hook size, and tension. Measure the swatch after the same washing and blocking treatment intended for the blanket, once fully dry. The weighed yarn must correspond to the entire measured rectangle: do not weigh a whole swatch and pair that mass with dimensions taken only across its centre. Exclude tools and unrelated yarn from the mass measurement.
Enter lengths in metres: 20 cm is 0.2 m. Positive dimensions are required. An unavailable calculation is not a zero yarn requirement.
The estimate assumes uniform yarn use per unit area. Different stitch patterns, gauge, borders, fringe and colour sections require separate consideration. An allowance cannot correct an unrepresentative swatch. See the Knitting and Crochet Gauge Calculator.
Lion Brand’s swatch planning guide describes scaling swatch yarn consumption by the project-to-swatch area ratio, adding a buffer and rounding to whole skeins. The mass formula here is an algebraic adaptation for the same yarn: with constant length per gram, the conversion between yarn length and mass cancels. The allowance is a user-selected planning margin, not a guarantee.
| Swatch | Blanket | Area ratio | Base yarn mass | Allowance | Total yarn mass | Skein mass | Whole skeins |
|---|---|---|---|---|---|---|---|
| 0.20 × 0.20 m; 12 g | 1.20 × 1.50 m | 45 | 540 g | 10% | 594 g | 100 g | 6 (5.94 rounded upward) |
| 0.15 × 0.20 m; 9 g | 0.90 × 1.20 m | 36 | 324 g | 15% | 372.6 g | 50 g | 8 (7.452 rounded upward) |
| 0.20 × 0.20 m; 12 g | 1.00 × 1.00 m | 25 | 300 g | 0% | 300 g | 100 g | 3 (already a whole number) |