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.