Do the math
before you cast on.

Gauge, yardage and needle sizes are the three places a project goes wrong. These tools turn your swatch into a number you can actually follow — no account, no app.

Open the cast-on calculator Substitute a yarn
39
yarns indexed
8
standard weights
0
sign-ups
10 cm / 4 in 10 cm 10 stitches
Gauge is a measurement, not a suggestion.
20 sts / 10 cm 100 stitches to cast on

01 — Tools

Four questions, answered with arithmetic.

No sign-up, no app. Each tool prints its formula so you can check the result by hand.

  1. 01

    Cast-on calculator

    Turn your gauge swatch and a finished width into the exact number of stitches to cast on.

    Gauge → stitches
  2. 02

    Yarn substitution calculator

    Convert metres and skeins when the original yarn is discontinued, unavailable, or simply not in your stash.

    Metres → skeins
  3. 03

    Needle & hook converter

    Metric, US and UK sizes in one table — plus the steel hook sizes that run backwards.

    mm ↔ US ↔ UK
  4. 04

    Yarn weight finder

    Work out which of the eight standard weights your yarn is, from gauge or wraps per inch.

    Gauge → category

02 — Reference

Needle sizes, without the guesswork.

US numbers are not standardised across manufacturers. Millimetres are. Use this table when a pattern gives you a number you don't recognise.

Full needle and hook charts

MetricUSUK
2.25 mm113
2.75 mm212
3.25 mm310
3.75 mm59
4 mm68
4.5 mm77
5 mm86
5.5 mm95
6 mm104
6.5 mm10.53
8 mm110
9 mm1300

03 — Library

Specs you can compare, not marketing copy.

Put-up, fibre, gauge and recommended tools for yarns people actually buy. Every record shows when it was last checked.

LaceFingeringSportDKWorstedBulkySuper BulkyJumbo
YarnWeightPut-upGaugeNeedle
Lion Brand Wool-Ease 4 · Worsted 85 g · 180 m (197 yd) 18 sts × 24 rows / 10 cm 5 mm
Cascade Yarns 220 4 · Worsted 100 g · 200 m (219 yd) 18–20 sts / 10 cm 4.5 mm / 5 mm
Stylecraft Special DK 3 · DK 100 g · 294 m (322 yd) 22 sts / 10 cm 4 mm
DROPS Lima 3 · DK 50 g · 100 m (109 yd) 21 sts × 28 rows / 10 cm 4 mm / 5 mm
Malabrigo Rios 4 · Worsted 100 g · 192 m (210 yd) 18–22 sts / 10 cm 4 mm / 5 mm
Bernat Blanket 6 · Super Bulky 300 g · 201 m (220 yd) 8 sts × 13 rows / 10 cm 8 mm

Browse all 39 yarns

04 — Guides

The reasoning behind the numbers.

49 guides, from measuring a swatch to buying the last skein.

  • 01

    How to measure gauge properly

    A swatch is only useful if you measure it the way you will wear it. Here is the sequence that produces a number worth calculating with.

    5 min read
  • 02

    Why your gauge is off (and what to change)

    Needle size is only one variable. Tension, fibre, stitch pattern and blocking all move the number — here is how to tell which one moved yours.

    6 min read
  • 03

    How to measure row gauge (and when it matters)

    Row gauge decides whether a raglan, sleeve cap or colourwork repeat fits. How to measure it, when it matters, and when to ignore it.

    6 min read
  • 04

    Gauge in the round vs flat

    Knitting in the round removes the purl rows, and that can change your gauge. How to swatch for circular knitting and what to do if the numbers differ.

    6 min read
Navy, ice-blue and cream yarn with wooden needles, a crochet hook and a gauge swatch

Good fabric starts before the first stitch.

The calculators assume a swatch you trust, a yarn you can identify, and a quantity that accounts for swatching, seaming and dye lots. These guides cover the parts arithmetic cannot see.

All guides

Method

Sizes follow the Craft Yarn Council's industry standards. Yarn specifications are recorded as facts — put-up, fibre content, gauge — and cross-checked against manufacturer and retailer listings.

Read the method