Crochet calculators that do the math for you
No more guessing how many skeins to buy or what hook to grab. Nine free tools for gauge, yarn substitution, sizing, and amigurumi math — built for crocheters, not spreadsheets.
Gauge Calculator
Convert a pattern's stitch count to match your own swatch gauge.
Yarn & Hook Converter
Find the right hook size and gauge range for any yarn weight.
Hook Size Chart
Convert between US, metric, and old UK/Canada hook sizes.
Yardage Estimator
Estimate how many skeins you need for a blanket, scarf, or garment.
Granny Square Calculator
Figure out how many squares you need for your target blanket size.
Flat Circle Calculator
Stop your circles from ruffling or cupping with a gauge-matched round plan.
Amigurumi Round Counter
Generate a round-by-round stitch count plan for any sphere size.
Hat Size Calculator
Cast-on count, body height, and crown decreases for any head size.
Garment Resizer
Scale a garment pattern up or down to your exact measurements.
Why gauge math matters
Crochet patterns are written for a specific gauge — the number of stitches and rows per inch a designer got with their yarn and hook. If your gauge comes out different (and it almost always does), your finished project will be a different size than the pattern promises. These calculators handle the proportional math so you can adjust stitch counts, hook sizes, and yarn quantities without doing it by hand.