Crochet gauge calculator: which hook should you actually use?
Crochet a small swatch, count the stitches, and enter three numbers. The calculator tells you the exact hook size to switch to — and projects your finished dimensions if you decide not to adjust.
Gauge helper
Crochet a swatch, count the stitches across it, and we'll tell you exactly which hook to switch to.
How to make a proper gauge swatch
- Use the exact yarn and hook the pattern calls for. Swatching with a different yarn to save the good one defeats the purpose.
- Crochet a square at least 15 × 15 cm (6 × 6 in). Small swatches lie — edges pull differently than the middle of a real project.
- Wash and block it exactly like the finished piece. Yarn relaxes after its first wash; a dry-swatch reading and a washed-swatch reading can differ by 10%.
- Count in the middle, at least 2 cm from any edge. Pick a specific 10 cm width (metric patterns) or 4 in (US patterns) and count exactly how many stitches fit.
- Enter that number here along with the pattern's target and the hook you used. The calculator does the rest.
Worked example: the cardigan that came out too big
A pattern calls for 20 single crochet in 10 cm using a 5.0 mm hook. Your swatch gives you 18. Enter 18 · 20 · 5.
The result: switch to a 4.5 mm hook. Your gauge is 10% too loose — going down one hook step brings you to target. The projection warns you that if you keep the 5.0 mm hook, the finished cardigan will come out about 111% of the intended size (11% bigger everywhere), which on a size M chest of 100 cm means 111 cm — the difference between fitted and boxy.
Reswatch with the 4.5 mm hook and re-run the calculator before starting the actual cardigan.
When gauge matters most (and least)
- Matters most: fitted cardigans, sweaters, tops, socks, hats, mittens, anything that has to fit a body measurement.
- Matters moderately: throws and afghans where a stated finished size matters (baby blankets to fit a specific crib, gifts to a specific size).
- Matters least: amigurumi (as long as the fabric is dense enough to hide stuffing, the exact final size doesn't break the toy), scarves, shawls, market bags.
Related tools
Gauge FAQ
Do I really need to make a gauge swatch?
For fitted garments — cardigans, sweaters, socks, hats — yes, always. Skipping the swatch on a cardigan almost always gives you a size 5–15% off, which is unwearable. For blankets, amigurumi and free-shape accessories, a swatch is optional; you can adjust as you go without ruining the project.
Why does hook size affect gauge more than yarn?
Yarn thickness is fixed once you buy it. Hook size directly controls how much space each stitch takes: a larger hook produces looser, wider stitches with the same yarn. One hook step (about 0.5 mm) typically shifts stitch count by ~1 stitch per 10 cm swatch.
What if I'm still off after switching hooks?
First check row gauge separately — some crocheters match stitch gauge perfectly but produce taller or shorter rows. If both are off after two hook adjustments, the yarn is the issue: try a different yarn from the same weight, or accept that this pattern won't work with this yarn.
What's the difference between stitch gauge and row gauge?
Stitch gauge counts how many stitches fit horizontally in a swatch. Row gauge counts how many rows stack vertically. Stitch gauge determines width; row gauge determines height. Most patterns care about stitch gauge more — but wearables with set-in sleeves care about both.