Granny square blanket calculator
Measure a blocked square's width and height, then enter your target blanket size. Add any join and outer-border width you plan; the grid can cover the target or choose the closest whole motif count.
Measure the square you will repeat
Use a blocked motif in the stitch pattern and yarn you plan to use. Measure width and height without joining or outer-border fabric. Rectangular motifs work too. If motif sizes vary, plan each size group separately.
With zero join and border allowance, a 15 × 15 cm square across a 100 × 120 cm target needs 7 across and 8 down: 56 squares. The grid finishes 105 × 120 cm. Dividing blanket area by square area would undercount because partial squares cannot fill the last column.
Plan yarn from an actual square
If you know the length used for one finished motif, enter it to scale the square fabric. Record joining and border yarn separately; their stitches do not repeat inside each square. For a label-based shopping count, take the total to the yarn quantity calculator.
Compare blanket size examples before choosing your target.