Hat Size Calculator
Find your cast-on or chain count, and get a crown shaping guide for knit or crochet hats.
Head Circumference Reference
| Size | Circumference | Age / Head Type |
|---|---|---|
| Preemie | 10" | Premature newborn |
| Newborn | 13" | Newborn (0–3 mo) |
| Baby | 14–16" | 3–12 months |
| Toddler | 17–18" | 1–3 years |
| Child | 19–20" | 3–12 years |
| Adult S/M | 21–22" | Average adult |
| Adult L/XL | 23–24" | Larger adult |
How to Use This Calculator
- Toggle between Knitting and Crochet mode.
- Select a head size preset or enter the head circumference in inches.
- Enter your gauge in stitches per inch (from a swatch worked in the round if possible).
- Adjust ease — hats are usually worked 1–2" smaller than the actual head size so they fit snugly.
- Click Calculate to get your cast-on count and a crown shaping guide.
Tips
- Hats knit in the round typically use negative ease (the hat is smaller than the head circumference).
- For a slouchy hat, use 0 ease or even 1–2" of positive ease.
- The crown shaping guide is a starting point — always check your pattern's specific instructions.
- If your stitch count doesn't divide evenly by the decrease number, round to the nearest multiple.
About this Hat Size Calculator
Use this free Hat Size Calculator to get quick, accurate results directly in your browser. It is designed for everyday use with no signup, no downloads, and no account required. No signup is required, and the tool works on phones, tablets, and desktop browsers.