Amigurumi Calculator — Increase & Decrease Rounds for 3D Shapes

This calculator uses your gauge and target diameter to work out the full amigurumi round schedule.

The formula

Circumference = Diameter x Pi

Max stitches = Circumference (cm) x Stitches per cm

Increase rounds = (Max stitches - Starting ring) / 6

Even rounds (sphere) = Increase rounds + 2

The published perfect-sphere rule is that the straight middle section runs for one more round than the flat circle — and the flat circle is the magic-ring round plus every increase round. Because this calculator lists the magic ring as round 1 (separate from the increase-round count), that works out to increase rounds + 2. For example, a flat circle of R1 (6 sts) through R7 (42 sts) is 7 rounds, so the body is 7 + 1 = 8 rounds — which is 6 increase rounds + 2. The decreases then mirror the increases. The calculator generates the full schedule of increase, even, and decrease rounds for your chosen shape.

Yarn estimate

Yarn used is roughly the average stitches per round times the total rounds. A round's stitch count is proportional to sin(angle) down the ball, so the average round is about 0.67 x the maximum (the mean of sin over a pole-to-pole sweep is 2/pi ≈ 0.64, nudged up because amigurumi rounds start from a small magic-ring cap rather than a single point). Multiply by your yarn-per-stitch factor for the length.