Yarn Calculator for Knitting & Crochet Blankets
To estimate yarn for a blanket, weigh a gauge swatch, divide the blanket area by the swatch area and multiply by the swatch weight. A 4 × 4 in swatch weighing 5 g means a 36 × 48 in blanket needs about 540 g, or about 594 g with a 10% buffer.
Worked example: a 36 × 48 in baby blanket
You knit a 4 × 4 in swatch in your blanket’s stitch pattern and it weighs 5 g. (This is an example; your own swatch weight will differ by yarn and stitch.) Your yarn comes in 100 g skeins.
- Swatch area: 4 × 4 = 16 sq in.
- Blanket area: 36 × 48 = 1,728 sq in.
- Ratio: 1,728 ÷ 16 = 108 swatches’ worth.
- Yarn: 108 × 5 g = 540 g.
- Add a 10% buffer: 540 × 1.10 = 594 g.
- Skeins: 594 ÷ 100 = 5.94, rounded up to 6 skeins.
How the yarn estimate works
yarn = swatch yarn × (project width × project height) ÷ (swatch width × swatch height) × (1 + buffer%)
- The method assumes yarn use is proportional to fabric area, which holds when the whole project uses the same stitch pattern and gauge.
- Make your swatch at least 4 × 4 in (10 × 10 cm), and wash and block it the way you will treat the finished piece.
- Limitations: separate borders, colourwork, cables and fringe use different amounts of yarn per area; estimate them separately or increase the buffer.
Craft Yarn Council standard yarn weights (knitting gauge)
| Category | Name | Typical yarn types | Knit gauge over 4 in (stockinette) | Recommended needles |
|---|---|---|---|---|
| 0 | Lace | Fingering, 10-count crochet thread | 33–40 sts | 1.5–2.25 mm (US 000–1) |
| 1 | Super Fine | Sock, fingering, baby | 27–32 sts | 2.25–3.25 mm (US 1–3) |
| 2 | Fine | Sport, baby | 23–26 sts | 3.25–3.75 mm (US 3–5) |
| 3 | Light | DK, light worsted | 21–24 sts | 3.75–4.5 mm (US 5–7) |
| 4 | Medium | Worsted, afghan, aran | 16–20 sts | 4.5–5.5 mm (US 7–9) |
| 5 | Bulky | Chunky, craft, rug | 12–15 sts | 5.5–8 mm (US 9–11) |
| 6 | Super Bulky | Super bulky, roving | 7–11 sts | 8–12.75 mm (US 11–17) |
| 7 | Jumbo | Jumbo, roving | 6 sts and fewer | 12.75 mm and larger (US 17+) |
Ranges are guidelines from the Craft Yarn Council. Always follow the gauge in your pattern.
Frequently asked questions
How do I know how much yarn a swatch used?
Weigh the finished swatch on a kitchen or jewellery scale that reads to 1 gram or better. Alternatively, measure the yarn before and after knitting or crocheting the swatch and use yards or metres.
Why add a buffer to the yarn estimate?
Edging, seams, joining, weaving in ends and small gauge changes over a large project all use extra yarn. A buffer of 10 to 15 percent helps you avoid running out, especially since a later skein may come from a different dye lot.
Does crochet use more yarn than knitting?
Crochet fabric is usually thicker and often uses more yarn for the same area than knitting with the same yarn. That is why measuring your own swatch, made in your stitch pattern, gives a better estimate than a general rule.
What yarn weight should I use for a blanket?
Medium (worsted, aran, Craft Yarn Council category 4) and bulky (category 5) yarns are popular for blankets because they work up quickly. Follow your pattern's recommended weight and check your gauge.
Can I use centimetres instead of inches?
Yes. The calculation only uses the ratio between the project area and the swatch area, so any unit works as long as the swatch and project use the same one.
Related calculators
Sources
- Standard Yarn Weight System — Craft Yarn Council
- Standards & Guidelines for Crochet and Knitting — Craft Yarn Council
- Yarn weight — Wikipedia
Disclaimer: results are estimates for general guidance only. Check product labels, recipes and project instructions before relying on them.