Project area is only a start
Two blankets with the same dimensions can use different yarn quantities because stitch structure, gauge, fibre and density differ.
Use a representative swatch
A washed swatch provides better evidence than a generic grams-per-square-metre value. Weighing a known swatch can refine the estimate.
Buy compatible dye lots
If colour consistency matters, buy enough from one dye lot and retain labels. Availability later is uncertain.
Practical checklist
- Include swatching and finishing in the allowance.
- Compare skeins by length as well as weight.