The form currently displays only the entered square side. It does not calculate a blanket layout, square count, finished dimensions or yarn estimate. Use the formulas and worked examples below for manual calculations.
Use metres for all lengths, including yarn. Divide centimetres by 100 before entering them: a 15 cm square is 0.15 m. Measure a finished square in the condition intended for the finished blanket. This model assumes identical square dimensions and a rectangular arrangement.
Joining allowance means the net extra width introduced by each internal join. It is added once between adjacent squares, not around every square and not around the outside edge. For n squares across, there are n − 1 joins. Enter 0 for a join that adds no width. Measure two joined squares and subtract twice the single-square width to estimate this allowance. These formulas assume a nonnegative allowance and do not cover joins that reduce the combined width.
The intended layout rounds upward to meet or exceed both target dimensions, excluding any border. Yarn per square is measured in metres and should include the tails you intend to allow for each square. Multiplying it by the square count estimates yarn for the squares only. Joining yarn, borders, additional waste and colour-specific purchasing quantities are excluded.
Source: direct algebraic derivation from the equal-square and internal-join assumptions stated here; these are not attributed to an external crochet standard.
Let s be the finished square side, a the added width per internal join, W and L the target dimensions, and y the measured yarn length per square. A line of n squares measures n × s + (n − 1) × a = n × (s + a) − a. Solving for the smallest whole count that meets a target gives the ceiling formulas below. Because s > 0, targets > 0 and a ≥ 0, each resulting count is at least one.
Columns C = ceil((W + a) / (s + a)); rows R = ceil((L + a) / (s + a)). Total squares N = C × R. Finished width = C × (s + a) − a; finished length = R × (s + a) − a. Square yarn length = N × y.
Here ceil means round upward to the next integer, leaving an exact integer unchanged. These formulas are provided for manual calculation; the form above does not evaluate them.
| Inputs | Whole-square layout | Finished dimensions | Yarn for squares |
|---|---|---|---|
| s = 0.15 m; W = 1.2 m; L = 1.5 m; a = 0.005 m; y = 25 m | C = ceil(1.205 / 0.155) = 8; R = ceil(1.505 / 0.155) = 10; N = 80 | 1.235 m × 1.545 m | 80 × 25 = 2000 m |
| s = 0.15 m; W = 1.2 m; L = 1.5 m; a = 0 m; y = 25 m | 8 columns × 10 rows = 80 squares | 1.2 m × 1.5 m | 2000 m |
| s = 0.15 m; W = 0.1 m; L = 0.1 m; a = 0.005 m; y = 25 m | 1 column × 1 row = 1 square | 0.15 m × 0.15 m; no internal joins | 25 m |