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Crochet circle increase calculator

Round-by-round instructions for a flat crochet circle of any diameter, with staggered increases so it stays round, in US or UK terms.

Built by Monhar Wesvak

Flat round rust and cream crochet mat with stitch markers and a wooden hook
Units
Stitch terms
Count rounds over 4 in (10 cm) of radius, from the centre out.
Add your stitch gauge to check the increase count suits your tension.
Working

Your result

Estimate

Fill in the fields above to see your result.

A modelled estimate. Real results vary with stitch, yarn and tension, so allow a margin.

A flat circle needs the same number of increases every round, and how many depends on how tall the stitch is. This calculator works out how many rounds reach your diameter, writes every round out in pattern style, and staggers the increases so the circle stays round instead of turning into a hexagon. Add your stitch gauge and it checks whether the standard increase count suits your tension.

How to use the calculator

  1. Choose the stitch.
  2. Enter the diameter you want and your round gauge: the rounds over 4 in (10 cm), counted from the centre.
  3. Optionally add your stitch gauge, to check the increase count suits your tension.
  4. Choose a continuous spiral or joined rounds, and whether to stagger the increases.

How the calculator works

Each round adds the same number of stitches, and each round adds two rounds' height to the diameter, one on each side of the centre:

Rounds = (diameter ÷ 2) × round gauge

Stitches in round r = increases per round × r

The increases per round follow the stitch height: 6 for single crochet, 8 for half double crochet (10 for a loose half double), 12 for double crochet and 16 for treble. Round 1 is worked into a magic ring, round 2 is 2 stitches in each stitch, and from round 3 each repeat has one more plain stitch than the round before.

A perfectly flat circle adds 2π × stitch gauge ÷ round gauge stitches each round. With typical tension that is about 6 for sc, 8 for hdc and 12 for dc; if your gauge gives a number at least 2 away from the standard count, the calculator warns you.

On even rounds from round 4, the plain stitches before the first increase are split between the start and the end of the round, so the increases do not stack into corners.

Reading your results

  • Rounds, stitches in the last round and stitches in the whole circle.
  • Finished diameter: from the whole number of rounds.
  • Round by round: every round written out with its stitch count. Joined rounds start with a turning chain and end with a slip stitch.
  • Warnings: a gauge mismatch, or a large circle that may start to ripple.

Worked example

A 10 in single crochet placemat at 4 rounds per inch (16 rounds per 4 in):

  • Rounds: (10 ÷ 2) × 4 = 20, ending with 6 × 20 = 120 stitches, 1,260 stitches in all.
  • Round 4: 1 sc, 2 sc in next st, *2 sc, 2 sc in next st* rep 5 times, 1 sc. (24 sts)
  • Round 5: *3 sc, 2 sc in next st* rep 6 times. (30 sts)
  • With 16 stitches per 4 in too, a flat circle needs 2π × 16 ÷ 16 = 6.3 increases a round, so 6 suits your tension.

US and UK terms

Flat circles add a set number of stitches each round, depending on the stitch's height:

  • US single crochet (sc) = UK double crochet (dc): 6 a round
  • US half double crochet (hdc) = UK half treble (htr): 8 a round
  • US double crochet (dc) = UK treble (tr): 12 a round
  • US treble (tr) = UK double treble (dtr): 16 a round

Switch the calculator to UK terms and the instructions use UK names; the counts stay the same.

Accuracy and limits

  • The rounds and counts are exact, and our automated tests check them. Whether the circle lies flat depends on your tension.
  • Large circles, such as rugs, often ripple after round 12 to 15; the calculator warns you. A plain round every 4 to 6 rounds usually fixes it.
  • In joined rounds of dc or tr where the starting chain counts as a stitch, work one stitch fewer in the first repeat so the count stays right.

Common mistakes

  1. Stacking the increases. Working the increase in the same place every round makes a hexagon. Keep the stagger on.
  2. Losing the start of the round. In a spiral, mark the first stitch of each round with a stitch marker.
  3. Changing hook partway. A different hook changes your gauge, and the circle starts to cup or ripple.

Tips for more accurate results

  • Measure the circle flat as you go. If it cups, add increases; if it ripples, work a round without increasing.
  • Start with a magic ring to close the centre.
  • To turn the finished circle into a square, use the circle to square calculator.

Frequently asked questions

How many stitches do I start a flat circle with?

The same number you add each round: 6 for single crochet, 8 for half double, 12 for double and 16 for treble.

Why does my circle look like a hexagon?

The increases are stacking in the same places every round. Stagger them: on alternate rounds, split the first plain stitches between the start and end of the round.

Why is my circle rippling?

It has more stitches than its radius needs, often from loose tension or a large circle. Go down a hook size, or work a plain round every few rounds.

Why is my circle cupping like a bowl?

It has too few stitches for its size. Go up a hook size, or add increases.

Spiral or joined rounds?

Spirals give a smooth edge with no seam, ideal for single crochet and amigurumi. Joined rounds keep taller stitches level and make colour changes neat, at the cost of a visible join line.

Related guides and tools

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