A worked example you can check
Three identical squares weigh 24g together, so one weighs 8g. A label stating 200m per 100g gives 16m per square. A grid of 6 × 8 squares contains 48 squares and needs an estimated 768m for the squares. If you enter another 60m for joins and a border in the same yarn, the total is 828m.
At 12cm per square, the unjoined grid is 72 × 96cm. That is not a promised finished blanket size: joining, borders, blocking and tension can change the result.
What to measure before trusting the estimate
- Make representative squares with the intended yarn, hook and stitch instructions.
- Weigh several together where practical, without labels or packaging. Keep the treatment of tails consistent.
- Record their size in the condition your pattern specifies.
- Estimate joining and border yarn separately. If those use a different colour, add a separate row in the shopping planner.
The transfer rounds the estimate up to the nearest 0.001m so it does not lose a small required length. It adds no automatic percentage. You can choose an allowance and subtract stash in the shopping planner.