One finished square answers everything: its size sets the grid, its weight sets the yarn. Measure and weigh your first square, enter the blanket you want, the count, the per-color totals, and the joining allowance follow.
Your Square and Blanket
Your Blanket Takes
130squares
10 × 13 · finishes 50 × 65 in
Weigh your real square, with its final rounds and colors, and these totals follow your hands, not a chart.
- Grid10 × 13
- Yarn per square19.8 yd (9 g)
- Blanket yarn + 10% joins2,832 yd · 1,287 g
- 100 g skeins13 · buy 14
The Formulas
squares = (width ÷ square) × (length ÷ square) · yarn = squares × one square’s grams × yards per gramjoins and border ≈ 10% on topWeighing one square beats any stitch-count estimate, because it measures your tension, your hook, and your yarn at once. The 10% rider covers joining rounds and a modest border; lavish borders deserve their own skein.
Worked Example
A 50 × 65 throw from 5 in squares that weigh 9 g, in 220 yd/100 g worsted:
- Grid: 10 × 13 = 130 squares.
- Yarn: 130 × 9 g = 1,170 g × 2.2 yd/g = about 2,574 yd, plus 10% for joins → 2,830 yd: call it 13 skeins of 100 g.
- Four colors? Weigh each round’s color once and the split follows the same arithmetic.
How to Measure Your Square
- Make the real square first, the one with your final rounds and colors: then measure it flat, unstretched.
- Weigh on a kitchen scale; under 10 g, weigh five squares and divide.
- Blocking changes size: if you’ll block, block the sample before measuring. A half inch per square is five inches across a throw.
Assumptions and Defaults
- Square grids of whole squares; the true finished size reports beside the target.
- Join allowance 10%: join-as-you-go runs leaner, whip-stitch leaner still, continuous borders fatter.
- Per-color splits follow the weights of each color’s rounds in the sample square.
Granny Questions, Answered
How many granny squares do I need for a blanket?
The number of granny squares for a blanket is the blanket size ÷ the square size in both directions, which gives 130 five-inch squares for a 50 × 65 in throw and 48 for a baby blanket. Larger squares bring the count down quickly, so the same throw in 10 in squares takes only 35.
How much yarn does one granny square take?
The yarn in one granny square comes from weighing it and multiplying the grams by the label’s yards per gram, so a 9 g square of 220 yd / 100 g worsted holds about 20 yd. Every estimate on this page builds on that one weighing, so it is worth doing carefully.
How much extra yarn do I need for joining granny squares?
Joining granny squares takes about 10% extra yarn, which covers join-as-you-go or sewn seams plus a simple border. A wide shell or ripple border is a project of its own, so give it a dedicated skein and keep the joining allowance for the seams alone.
How do I split granny square yarn across colors?
To split granny square yarn across colors, weigh the sample square’s rounds by color, or make one square in each color arrangement and weigh each. The per-color grams then scale by the square count, just like the overall total.