Tools
Crochet Yarn Calculator: How Many Balls Do I Need?
Choose a project or enter your own size, pick the main stitch and your yarn, and get the total length, weight and number of balls, with a safety margin.
Free · No sign-up · Runs in your browser
Quick reference: how much yarn each project needs
| Project | Size | 2 – Fine · 300 m/100 g | 3 – Light · 230 m/100 g | 4 – Medium · 170 m/100 g | 5 – Bulky · 110 m/100 g |
|---|---|---|---|---|---|
| Baby blanket | 75 × 90 cm | 1,050 m (1,150 yd) · 350 g | 920 m (1,010 yd) · 400 g | 790 m (870 yd) · 465 g | 640 m (700 yd) · 580 g |
| Bed blanket | 150 × 200 cm | 4,690 m (5,130 yd) · 1,560 g | 4,100 m (4,490 yd) · 1,785 g | 3,530 m (3,860 yd) · 2,075 g | 2,840 m (3,100 yd) · 2,580 g |
| Sweater size M | 100 × 62 cm | 1,600 m (1,750 yd) · 535 g | 1,400 m (1,530 yd) · 610 g | 1,200 m (1,320 yd) · 710 g | 970 m (1,060 yd) · 880 g |
| Scarf | 20 × 180 cm | 560 m (620 yd) · 185 g | 490 m (540 yd) · 215 g | 420 m (460 yd) · 250 g | 340 m (370 yd) · 310 g |
| Hat | 54 × 21 cm | 160 m (170 yd) · 55 g | 140 m (150 yd) · 60 g | 120 m (130 yd) · 70 g | 100 m (110 yd) · 90 g |
| Amigurumi (~20 cm) | 30 × 30 cm | 140 m (150 yd) · 45 g | 120 m (130 yd) · 55 g | 110 m (120 yd) · 60 g | 90 m (90 yd) · 75 g |
How it works: the math behind the tool
The estimate starts from the surface you will crochet: width × height × a project factor (1.65 for a sweater with sleeves and neckband, 2 for a two-sided bag, 0.9 for a hat).
Thinner yarns have more meters per 100 g and cover less surface per meter. Yarn thickness is proportional to 1/√density, so the length needed grows with the square root of the density. The 0.82 constant calibrates the model to about 10.7 m per 10 × 10 cm of double crochet in worsted yarn (about 170 m per 100 g).
Length (m) = surface (cm²) ÷ 100 × 0.82 × √(m per 100 g) × Ks × (1 + margin)
Ks is the stitch consumption factor relative to double crochet (1.00): mesh 0.75, half double 1.15, moss 1.20, single crochet 1.30, waffle 1.85, puff 2.40, jasmine 3.10. Weight is length ÷ density × 100, and the number of balls is always rounded up.
Tension can change real consumption by around ±15 %, so the default safety margin is 10 %.
The calibration constant and the square root of density
The formula metres = (area ÷ 100) × C × √ρ × Ks × (1 + margin) uses an empirical constant C of 0.82, the value that brings the model in line with swatches measured in double crochet. The square root of the density ρ (metres per 100 g) expresses that a thinner yarn has more metres per gram but also needs more, smaller stitches to cover the same area. Doubling the density therefore increases the length by about 41 %, not 100 %.
Project presets and surface factors
Each preset starts from real measurements: a baby blanket of 75 × 90 cm, a bed blanket of 150 × 200 cm, a scarf of 20 × 180 cm and sweaters from size S to XXL. A surface factor adds what a flat rectangle does not cover: 1.65 for the sleeves and collar of a sweater, 0.9 for the decreasing crown of a hat and 2.0 for the two faces of a bag. You can overwrite any measurement and the result updates at once.
From metres to balls
The length is converted to grams with the density of your yarn and then divided by the length of one ball, using the ball data of the yarn you pick or the typical ball of its Craft Yarn Council weight. The calculator shows the exact figure and rounds it up to whole balls. The safety margin, adjustable from 0 to 25 %, covers tension changes, the swatch and weaving in ends. Buy every ball from the same dye lot, because a second lot can show a visible line in the fabric.
Last updated: November 3, 2026
Frequently asked questions
How many balls of yarn do I need for a baby blanket?
A 75 × 90 cm baby blanket in double crochet with worsted yarn (about 170 m per 100 g) needs around 790 m with a 10 % margin, which is 5 balls of 100 g. The same blanket in single crochet uses about 30 % more yarn.
Which crochet stitch uses the most yarn?
Textured stitches: puff, bobble and jasmine stitches use two to three times more yarn than double crochet for the same surface. Mesh (filet) stitches use the least.
Why does single crochet use more yarn than double crochet?
Single crochet is short and dense, so you need more stitches and rows to cover the same surface, and every stitch adds loops. Double crochet covers more height with each stitch.
Can I calculate in yards and ounces?
Yes. Switch to imperial units and every field is converted to inches, yards and ounces. Results always show both meters and yards.