Yarn calculator

The yarn calculator above works out how many skeins (the wound bundles yarn is sold in) to buy for a knitting or crochet project. It starts from your swatch, the small test square you knit or crochet before a project, and from your yarn label’s yards and grams per skein. The same swatch gives your gauge (how many stitches fit in 4"), and the gauge calculator turns that into stitch counts.

How to use the yarn calculator

1. Your swatch: its width and height, then what it weighs or, with no scale, the yarn it used.
2. Your project: the finished width and length. For a garment, run each piece as its own rectangle, and put identical pieces in “How many pieces this size”. Leave the shape factor (a multiplier for shaping) at 1: we found no checkable source for other values.
3. Planning margin and yarn label: keep the 10% or change it, then type the label’s yards and grams per skein (skein sizes differ: see how many yards in a skein).
4. Read the skein count, then check each line of “Show the math” against your numbers.

Why a swatch, not a yardage chart

Yardage charts disagree. Jason Ramirez of FiberTools, whose method this calculator follows, says as much: “Two charts can give very different answers for the same 50-by-60-inch throw, and neither one is necessarily careless.” Charts rest on different stitches, hooks, yarns and tension, he notes.

The pages we read don’t name the gauges or sources behind their figures. Lion Brand’s chart page puts an afghan (a blanket or throw) in its Yarn Weight 4 column (yarn weight here means thickness, not grams; see the yarn weight chart) at “2250-3125 Yards”, with no size or stitch for the row. AriYARN, a yarn shop that also teaches swatch math, says its ranges assume “normal human variation” in gauge, stitch choice, and how the piece is finished. Briana K, a crochet designer, says her project-type numbers “come from published yardage charts”, without naming them.

Gauge doesn’t settle it either, Ramirez writes: “Gauge alone does not tell you how much yarn those stitches consume.” Two squares the same size can hold very different lengths of yarn, and your swatch’s weight measures that. Haven’t chosen a yarn or stitch yet? A chart is useful at that stage, he says. After that: “A weighed swatch becomes more useful once the actual project decisions have been made.”

How to weigh or measure your swatch

Work it in the project’s yarn, needle or hook size, and stitch pattern, and make it, Ramirez says, “at least four inches square; six inches gives you more interior fabric and makes the result less dependent on edge stitches.”

Use grams. Ramirez’s reason: “Small gram measurements are easier to work with than rounded ounces.” A digital kitchen scale that reads grams in 1 g steps ad is one option.

Measuring the yarn instead works, but Briana K names the trade-off: “Weighing is faster and more precise than measuring a long tangle of unraveled yarn against a tape measure.”

The 10% margin, and when to raise it

The 10% in the margin field is Ramirez’s own habit, not a rule or a guarantee.

AriYARN, a yarn shop, gives a range rather than one number: “A smart buffer is usually 10–15%—more for cables, textured stitches, and blankets.” (Cables are stitches crossed over each other to make twisted ropes.) The 15% row in the worked example shows what a bigger margin changes.

If the total looks high, Ramirez says not to trim it: “Do not cut the number down because it seems high.” Check the inputs and make a second swatch instead.

Then buy every skein at the start. Doing so, Ramirez says, “also protects you from color differences and unavailable stock later.”

What one swatch can’t measure

The box above lists what one swatch misses; Ramirez’s notes say what to do:

• Swatch each stitch pattern: “Make a swatch for each major stitch pattern and estimate its section separately.” Run the calculator once per section.
• Work out each color yourself: the total “does not tell you how much of each color to buy unless you calculate the color proportions.”
• Finish the swatch like the project: blocking (wetting or steaming a finished piece and drying it to shape) matters, because “Fiber behavior can change the dimensions.”
• Re-measure as you go: your tension (how tightly you work the yarn) can drift over a long project. “Periodically compare the blanket to the swatch and measure again.”

Worked example: a 36" × 36" baby blanket

Say you knit or crochet a 4" × 4" swatch that weighs 9 g, for a 36" × 36" baby blanket, in a yarn whose label gives 220 yd per 100 g. These figures are made up. The blanket is 81 swatches’ worth of fabric:

The 0% row is the bare swatch math, shown so you can see what the margin adds; we wouldn’t buy to it. The margin always adds yardage, but the skein count changes only when the total crosses a whole skein. Type these figures above to see each step in “Show the math”. Making a scarf, hat or sweater instead? See how much yarn for a scarf, hat or sweater.

FAQs

Does crochet use more yarn than knitting?

It can, says AriYARN: “Crochet stitches often build a thicker fabric for the same surface area, which can increase yardage.”

Can I use a project I’ve already started as the swatch?

Briana K suggests it when you’re running short: measure what you’ve made, weigh or measure the yarn it took, and “treat that as your swatch.” A piece still on the needles or hook hasn’t been washed or blocked, though, so in our view its size and weight may change once it is.

How accurate is a yarn calculator?

Ramirez on his own method: “The important word is estimated. This is much more personal to the project than a broad yardage chart, but it is not a promise from the yarn universe.”