Crochet cone and cylinder calculator

Christmas trees, gnome hats, witch hats, carrots, horns and toy legs are cones or tubes. This calculator writes one round by round from the height and diameters you want and your gauge, spreading the increases evenly so the sides are smooth.

How to use the calculator

1. Choose a pointed cone, a tapered tube (wider at one end) or a straight tube.
2. Enter the height and the bottom diameter, and the top diameter for a tapered tube.
3. Enter your stitch and round gauge over 4 in (10 cm).
4. Work in a continuous spiral of single crochet, from the top down.

How the calculator works

The fabric runs along the slanted side, not straight up, so the rounds come from the slant height:

Slant height = √(height² + (bottom radius − top radius)²)

Rounds = slant height × round gauge

Bottom round = 2π × bottom radius × stitch gauge

A cone starts from 6 sc in a magic ring; a tapered tube starts from its top circumference; a straight tube keeps the same count all the way. The counts in between rise in a straight line, and each round's increases are spread evenly around it.

Reading your results

• Slant height and rounds.
• First and last round: the stitch counts at the top and bottom.
• Round by round: every round written out. For a tube, the first round tells you how to start, and a note covers the base.
• Warnings: if the shape is so flat that it is nearly a circle, the calculator suggests the flat circle calculator instead.

Worked example

A cone tree 8 in tall and 12 in across the base, at 4 stitches and 4 rounds per inch:

• Slant height: √(8² + 6²) = √100 = 10 in.
• Rounds: 10 × 4 = 40.
• Stitches: from 6 at the tip to 2π × 6 × 4 = 151 at the base.

Using the 8 in height instead of the slant would give only 32 rounds, and the tree would come out about 20% too short.

Accuracy and limits

• The counts are exact and covered by our automated tests; the shape depends on your tension and stuffing.
• A cone always starts at 6 stitches: very sharp tips are hard to turn out.
• A straight tube works even after its base. Make a closed base first with the flat circle calculator, or start from a chain ring for an open tube.

Common mistakes

1. Using the height for the rounds. The fabric follows the slant, which is longer than the height for any cone or tapered tube.
2. Stacking the increases. Spread them as the instructions show; stacked increases make visible ridges.
3. Stuffing too lightly. A tall cone slumps unless it is stuffed firmly or has a card insert.

Tips for more accurate results

• Mark the first stitch of each round with a stitch marker.
• For a hat, measure your gauge in the round, as you will work it.
• A cone on a sphere makes a gnome or a toy's nose: the amigurumi sphere calculator writes the ball.

Frequently asked questions