How much yarn do I need? Count backwards from the project.
You’re standing in the shop holding three skeins of a heathered teal you’ll never see again, and the only honest question is: will it be enough? The answer isn’t grams. It’s metres — and the size, the gauge, and the thing you actually mean to make. Count backwards from the finished object.
Count backwards from the finished thing
The mistake is to start at the yarn. You see a colour, you fall for it, and then you ask what it could become. Reverse it. Start at the object — adult sweater, newborn blanket, one long scarf — then its size, then the gauge it’ll knit at. Each of those narrows the number. A garment is just surface area in disguise: the bigger the body, the slower the stitch, the more texture you pack in, the more metres it drinks.
So the real chain is: what you’re making, then how big, then how dense the fabric, then how much margin for swatching and second-guessing. Get those four and the metres fall out almost on their own.
Metres, not grams — the ball band’s most useful number
Two balls can both say 50g and behave nothing alike. One is a crisp fingering at 210m; the other a plump aran at 80m. Grams measure the weight of fibre in your hand; metres measure the distance it’ll travel through your needles. A pattern is written in distance, so you shop in distance. Always read the metres-per-ball line first — it’s usually printed right beside the grams, in a slightly smaller font, easy to skim past at 11pm.
This is exactly the figure YarnScope’s OCR lifts off the band when you scan it: brand, weight category, and the metres-per-ball, so the number that actually matters is the one stored against the skein — not a vague “about a ball’s worth” you’ll misremember by spring.
Rules of thumb by project (adult, stockinette, metric)
These are honest middle-of-the-road ranges for a standard adult size in plain stockinette. Treat the low end as fingering/4-ply territory and the high end as worsted-and-up, and read the notes underneath — texture and ease move these fast.
- Socks (a pair) — fingering: 350–420m. One 100g sock ball usually does an average adult pair, with a little left for darning later.
- Scarf — DK/worsted: 200–350m. A skinny 1.5m scarf sits low; a generous wrappable one sits high.
- Shawl — fingering/lace: 400–900m. A small triangle starts near 400m; a proper shoulder-swallowing lace shawl climbs to 800–900m.
- Baby blanket — DK: 700–1,100m. A pram square is near the bottom; a cot-sized blanket near the top.
- Adult sweater — DK/worsted: 1,000–1,800m. A cropped fitted pullover hovers around 1,000–1,200m; an oversize aran tunic with a shawl collar reaches 1,800m and keeps going.
Then adjust. Stranded colourwork can want 1.5×–2× the plain figure, because every round carries two yarns. Dense cables and full-coverage lace add roughly 15–25%. Oversize ease is sneaky — going up two sizes or adding 15cm of positive ease quietly adds a few hundred metres to a sweater. And whatever the project, budget 10% for the swatch and the inevitable frog.
Always buy one extra ball — same dye lot
This is the rule that saves the most heartbreak, so it gets its own heading. When you’re near the edge of “enough”, buy one more ball than the maths says — from the same dye lot. Dye lots drift; the teal you bought today and the teal you come back for in August can differ just enough to draw a faint tide-line across a yoke, visible only in daylight, only after blocking, only when it’s too late. An extra ball in the right lot is cheap insurance. A leftover ball is a future hat. A second sleeve in the wrong lot is a reknit.
YarnScope captures the dye lot at scan time precisely so this is answerable later — you can filter your stash to “fingering, teal, lot 4471” and know in seconds whether you already own a continuous block or a patchwork of near-matches.
Do I already own enough? Ask the stash, not your memory
Half the time the honest answer to “how much yarn do I need?” is “less than you think, because you already own most of it.” Human memory is terrible at metres. You’ll swear you’ve a sweater’s worth of that grey, and it’ll turn out to be three odd balls in three lots adding up to a generous hat. So don’t trust the recollection — query the stash.
In YarnScope you filter by weight category and colour, and the app totals the metres you hold in that one combination. If the pattern wants 1,400m of worsted and you’re holding 1,150m across matching skeins, you know the exact gap before you reach for your card — buy two balls, not a fresh sweater’s worth, and not nothing.
Reserve the skeins so you don’t spend them twice
The other half of the problem is double-allocation. You mentally earmark the same eight balls of DK for both the cardigan and the blanket, then cast on the cardigan and find the blanket’s been quietly robbed. When you start a project in YarnScope you reserve its skeins to it. Reserved balls drop out of your “available” totals, so the next time you’re costing a project the maths only counts yarn that’s genuinely free. Finish or frog the project and the reservation releases the skeins back into the pool — nothing’s deleted, it just stops pretending to be in two places at once.
If you’re arriving with years of stash already on Ravelry, the CSV export imports in one paste — metres, weight, and dye lot map straight across — so the totals are honest from day one rather than after a fortnight of re-typing.