How to use the granny square blanket calculator
- Enter the blanket width and length you want, in inches.
- Enter the finished size of one square. Measure a square after blocking, because it can differ from the pattern.
- Choose how to round the count: up so the blanket is at least the size, down so it is no larger, or to the nearest square.
- Open More options to add a border or the yarn one square uses, and read the squares and the real finished size.
Formula
squares across = (blanket width - 2 x border) / square size, rounded
squares down = (blanket length - 2 x border) / square size, rounded
total squares = across x down
real size = squares x square size + 2 x border
Whole squares rarely match the target size exactly, so the page shows the real finished size and how far it is from your target.
A 48 by 60 inch blanket of 6 inch squares
48 / 6 = 8 squares across and 60 / 6 = 10 down, so 8 x 10 = 80 squares. With 12 yards of yarn per square and 10% extra, the squares need 80 x 12 x 1.1 = 1,056 yards.
For a 50 by 62 inch target, rounding up gives 9 by 11 squares, which is 99 squares and a 54 by 66 inch blanket. Rounding down gives 8 by 10, or 80 squares. With a 3 inch border the squares fill the 42 by 54 inches inside it, so 7 by 9 = 63 squares are enough for a 48 by 60 inch blanket.
Measuring your own squares
Pattern sizes are a starting point. Hook size, yarn and tension all change the finished square, and blocking can stretch it. Make one square, wash and block it the way you will care for the blanket, then measure. A square that is an inch off can change the blanket by several inches.
Joining squares with a seam or a crocheted join adds or removes a little size. After joining a few squares, measure the strip and check the plan again.
Yarn and related tools
Count the yarn by weighing a finished square against the full skein. The Yarn Yardage Calculator helps estimate yardage for other projects, and the Crochet Chain Calculator works out a starting chain. For gauge on knit pieces, see the Knitting Gauge Calculator, and for a pieced quilt layout, the Quilt Sashing and Border Calculator.
Assumptions and limits
- All squares are the same size and are joined edge to edge with no gap.
- A border is the same width on all four sides.
- The yarn per square and the extra for joining are your own measurements or examples.
- The page always plans at least one square in each direction.
Frequently asked questions
How many granny squares do I need for a blanket?
Divide the blanket width and length by the square size, round each to a whole number, and multiply. A 48 by 60 inch blanket of 6 inch squares needs 8 by 10, or 80 squares.
Should I round the square count up or down?
Round up if the blanket should be at least the target size, and down if it must not be larger. The page shows how far each choice is from your target.
How do I add a border to the count?
Enter the border width in More options. The squares then fill only the space inside the border, so fewer squares are needed.
How much yarn do I need for the squares?
Multiply the squares by the yarn one square uses, and add a cushion for joining and weaving in ends. Enter the yarn per square in More options and the page does the sum.