Yarn Calculator
Calculate how much yarn you need for knitting or crochet projects based on project type and size.
Plan your yarn purchases.
Yarn weight classification determines which needle size to use, what gauge to expect, and how a finished fabric drapes and feels. Every yarn is classified into one of eight standard weights, each with associated needle sizes, hook sizes, and typical stitch gauge.
Gauge formula: Stitches per 4 inches = Gauge × 4 Or rearranged: Gauge (stitches/inch) = Pattern Gauge ÷ 4
Needle size to yarn weight selection: Needle diameter (mm) = f(yarn weight category) — a lookup relationship, not a strict formula.
Substituting yarns — meterage per gram formula: Meters per gram = Total Meterage ÷ Skein Weight (grams) If substituting yarn B for yarn A: Skeins of B needed = (Pattern Yardage ÷ B Meterage per Skein)
What each variable means:
- Weight — in yarn, “weight” describes thickness, not heaviness; a “bulky weight” yarn is thick, not necessarily heavy per skein
- WPI (Wraps Per Inch) — wrap the yarn around a ruler; count wraps per inch to determine weight category: 30+ WPI = lace, 18–20 WPI = fingering, 12 WPI = worsted
- Gauge swatch — the only accurate way to verify needle compatibility; knit a 6×6 inch swatch, measure stitches per 4 inches after washing; adjust needle size up or down until your gauge matches the pattern
- Twist — tightly twisted yarns are durable and stitch-definition is high; loosely plied or single-ply yarns are softer but pill more easily
Standard Craft Yarn Council (CYC) weight system:
| # | Name | Knit Gauge (4") | US Needle | Hook |
|---|---|---|---|---|
| 0 | Lace | 33–40 sts | 000–1 (1–2.25mm) | B/1 |
| 1 | Super Fine | 27–32 sts | 1–3 (2.25–3.25mm) | B/1–E/4 |
| 2 | Fine | 23–26 sts | 3–5 (3.25–3.75mm) | E/4–7 |
| 3 | Light (DK) | 21–24 sts | 5–7 (3.75–4.5mm) | 7–I/9 |
| 4 | Medium (Worsted) | 16–20 sts | 7–9 (4.5–5.5mm) | I/9–K/10.5 |
| 5 | Bulky | 12–15 sts | 9–11 (5.5–8mm) | K/10.5–M/13 |
| 6 | Super Bulky | 7–11 sts | 11–17 (8–12.75mm) | M/13–Q |
| 7 | Jumbo | 6 or fewer sts | 17+ (12.75mm+) | Q+ |
Worked example: Pattern calls for worsted weight (CYC #4), 18 sts per 4 inches on US 8 (5mm) needles. You want to substitute with a DK weight yarn you already own.
- DK (CYC #3) has 21–24 sts per 4 inches
- Going down in weight means more stitches per inch → smaller fabric
- Recommended: swatch DK on US 6 (4mm) needles first; you may need to increase needle size to US 7–8 to match gauge; the fabric will be slightly drapier and lighter than the pattern intends