Yarn Calculator

How much yarn a project takes depends on the project, the size, and how many yards are on the ball you are buying. This calculator works from the yardage table below, adds a buffer, and divides by your skein length.

Yards needed by project (worsted weight, medium/adult size):

Small is three quarters of the medium figure and large is 1.35 times it. Every number then gets a 10% buffer on top before the skein count is worked out, which is not padding: dye lots differ, and running out with two rows to go means either a visible colour change or unravelling a sleeve. Buy the extra ball at the start.

Yarn weight matters more than the table suggests. Those figures assume worsted, CYC #4. Working the same garment in fingering can take half as much again in yardage, because thinner yarn means more stitches to cover the same area. Bulky goes the other way. If your pattern gives a yardage, use the pattern’s number; this table is for when you are working without one.

Substituting one yarn for another: Skeins needed = Total pattern yardage ÷ yards per skein of the new yarn

That is the arithmetic this calculator does. What it cannot do is tell you the fabric will behave the same, which is the actual risk in a substitution.

Gauge, and why it decides everything: Stitches per 4 inches = stitches per inch × 4

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:

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