How to Calculate How Much Yarn Is Left in a Skein
Divide the weight of the yarn you have left by the weight of a full skein, then multiply by the length printed on the ball band. With 37 g left of a 100 g skein labelled 220 yd: 37 ÷ 100 = 0.37, and 0.37 × 220 = 81.4 yd. This guide works that through by hand, in three unit combinations, and covers the two situations the formula cannot handle.
What You Need
Three numbers and a scale. Two of the numbers are printed; only one is measured.
| Input | Where to find it | Example | Why it matters |
|---|---|---|---|
| Original skein weight | Ball band | 100 g | The denominator. It sets what “a whole skein” means. |
| Original skein length | Ball band | 220 yd | The baseline length the proportion is applied to. |
| Remaining weight | Your kitchen scale | 37 g | The numerator. It is the only figure you measure yourself. |
A kitchen scale reading to 1 g is enough. If the ball band is gone, skip to the sample method, which needs no label at all.
The Remaining Yarn Formula
Remaining length = remaining weight ÷ original weight × original length.
It works because a skein is the same yarn all the way along, so the fraction of the weight that remains is the fraction of the length that remains.
Step-by-Step Method
Find the original skein weight
Read it from the ball band. It is the weight of a full skein as sold — 100 g in the example above. If you bought several sizes of the same yarn, make sure you have the band for the size in your hand.
Find the original skein yardage or meterage
Also from the band, and usually printed in both units: 220 yd and about 74 m for this skein. Either works. Whichever you use is the unit your answer comes out in.
Weigh your remaining yarn
Take off the band, the tie and any core, zero the scale, and weigh what is left: 37 g. This is the only figure you measure, and it is where most of the error enters.
Calculate the proportion
Divide the remaining weight by the original weight: 37 ÷ 100 = 0.37. That is the fraction of the skein still there, or 37%.
Convert to remaining length
Multiply the proportion by the original length: 0.37 × 220 = 81.4 yd, about 74 m. Subtract from the original to get what you used: 220 − 81.4 = 138.6 yd.
Worked Example in Grams and Yards
A skein labelled 100 g / 220 yd. The leftover weighs 37 g.
37 ÷ 100 = 0.37. Then 0.37 × 220 yd = 81.4 yd remaining, which is about 74 m. That leaves 138.6 yd used, and 37% of the skein still on the ball.
Worked Example in Grams and Meters
A skein labelled 150 g / 300 m. The leftover weighs 62 g.
62 ÷ 150 × 300 m = 124 m remaining, about 136 yd. That is 41.33% of the skein, with 176 m used.
The proportion here is 62 ÷ 150 = 0.4133…, which does not terminate. Work it in one chain rather than rounding it first: rounding to 0.4133 and then multiplying gives 123.99 m, which is close enough in practice but is not the same number. Note also that the answer arrives in metres because the label was in metres — the length unit passes straight through.
Worked Example in Ounces and Yards
A skein labelled 6 oz / 315 yd. The leftover weighs 2.2 oz.
2.2 ÷ 6 × 315 yd = 115.5 yd, about 106 m, with 199.5 yd used. The proportion is 36.67%, another one that does not terminate — so again, chain the sum rather than rounding partway.
Convert that skein to grams and run the sum again and it returns 115.5 yd once more. The weight unit cancels: it sits above and below the division line, so it disappears before the multiplication happens. Practically, that means an American ball band in ounces and a scale set to grams are not a problem — switch the scale, not the arithmetic.
How to Weigh Yarn Accurately
The scale's resolution sets a floor on how precise the answer can be. On the 100 g / 220 yd skein, a scale reading to 1 g means 37 g is really somewhere between 36.5 and 37.5 g — which is 80.3 to 82.5 yd, a band of 2.2 yd. That is not a fault in the method; it is the honest width of the answer.
What If the Label Is Missing?
Then you cannot use the formula above, because there is no original weight or length to divide by. There is a second method that needs no label, and it has one real advantage: it measures your actual yarn rather than the manufacturer's nominal figures.
Measure a known length of the leftover, weigh that sample, and divide. 10 yd weighing 4 g is 10 ÷ 4 = 2.5 yd per gram. Multiply by the whole remaining weight: 37 g × 2.5 = 92.5 yd.
The catch is that the sample now carries the scale error, and a short sample carries it badly. Here is the same 37 g estimate from three sample lengths, on a scale reading to 1 g.
| Sample measured | It weighs | Length per gram | Estimate for 37 g | Range this allows |
|---|---|---|---|---|
| 10 yd | 4 g | 2.5 yd/g | 92.50 yd | 82.22 – 105.71 yd (23.49 yd wide) |
| 20 yd | 8 g | 2.5 yd/g | 92.50 yd | 87.06 – 98.67 yd (11.61 yd wide) |
| 40 yd | 16 g | 2.5 yd/g | 92.50 yd | 89.70 – 95.48 yd (5.79 yd wide) |
Measure as long a sample as you can bear to. Ten yards leaves a band of 23.5 yd; forty yards narrows it to 5.8 yd from the same scale. Wind the sample around something of known circumference, or count arm-lengths against a tape, and keep the tension light.
If you also want to know what kind of yarn it is rather than just how much, that is a different measurement: wraps per inch identifies thickness from an unlabelled strand, and the WPI calculator matches a reading against the published weight ranges.
What If the Yarn Is on a Cone or Cardboard Core?
Everything on the scale is counted as yarn, so a core inflates the answer. The fix is arithmetic, not estimation: weigh an identical empty core and subtract it.
A gross reading of 61 g with a 24 g core is 37 g of yarn, giving 81.4 yd on our example skein. Leave the core on and the same yarn reads 134.2 yd — 52.8 yd of yarn that does not exist, which is the kind of error that has you starting a project you cannot finish.
Where no spare core exists, unwind the yarn onto a scrap of paper, weigh the empty core once it is free, and note the figure for next time. Cones from the same supplier are usually consistent.
Why Your Result Is an Estimate
The arithmetic is exact. The inputs are not, and there are three separate reasons.
Your scale has a resolution. It is the one source of error that can be quantified exactly, and the range above shows how.
The two label figures are specifications, not measurements. They tell you what that product is sold as. Your particular skein was wound by a machine to a target, and how close it landed is not something any manufacturer publishes, so no number is put on that here — it is a reason the answer is approximate, not a quantity to subtract.
Whatever else sits on the scale is counted as yarn. The core case above shows how far that can push a figure.
None of that makes the method useless. It makes it an estimate, which is exactly what it is for: deciding whether a leftover is worth keeping, and roughly what it might do.
How to Use the Remaining Yardage
A yardage on its own decides nothing. It becomes useful the moment you set it against a requirement, and there are two ways to get one.
A written pattern states its yardage per size, so the comparison is direct. Where there is no pattern — a scarf you are making up as you go, a border of your own — the requirement has to be derived from gauge and finished dimensions, which is what estimating yardage for a project does. Where the leftover is close but short, bringing in a second yarn is the usual route, and it changes drape and dye lot as well as quantity.
Whichever way you get the requirement, treat a near-miss as a no. This estimate carries a range, and a leftover that matches your need to within a few yards is inside that range rather than clear of it.
When This Formula Should Not Be Used
The proportion holds only while every gram on the scale is the same yarn the label describes. Six situations break that, and the first is the one people hit most.
| Situation | Why the formula breaks | What to do instead |
|---|---|---|
| Leftovers from two different yarns weighed together | One label cannot describe both. 44 yd of one plus 80 yd of another is 124 yd, but running the combined 40 g through a single label gives 88 yd — out by 36 yd. | Separate the yarns and calculate each against its own label. |
| The original product is unknown | There is no denominator and no baseline length to scale. | Use the sample method below, which needs no label at all. |
| A cone or core is still on the scale | Its weight is read as yarn. A 24 g core adds 52.8 yd that does not exist. | Remove it, or weigh an identical empty core and subtract. |
| The label is from a different skein size | The denominator has to be the size you actually bought; the same yarn in another put-up has different figures. | Find the figures for the size you actually bought. |
| Thick-and-thin, slub or deliberately uneven yarn | The yarn is not the same all the way along, so weight and length are not proportional. | Treat any figure as a rough guide, and measure directly if it matters. |
| Yarn that has been wet and is not fully dry | Water has weight and reads as extra length. | Let it dry to room conditions before weighing. |
Where the Arithmetic Goes Wrong
Rounding the proportion before multiplying. The second and third examples above both produce recurring decimals. Round to four places first and the answer shifts by a hundredth of a metre; round to two and it shifts further. Carry the division through in one chain.
Dividing the wrong way round. Remaining over original, not original over remaining. If your answer is longer than the full skein, this is why.
Multiplying by the weight instead of the length. The proportion is dimensionless; what it multiplies is the labelled length. Multiplying by the labelled weight gives a number in grams that means nothing.
Taking the sample measurement under tension. On the no-label method, stretching the sample as you measure it inflates the length and therefore the yards-per-gram figure. Keep it slack.
Reusing a yards-per-gram figure across different yarns. It is a property of one yarn, derived from one sample. It does not travel.
Use the Remaining Yarn Calculator
The same arithmetic, with unit handling, multiple skeins and the scale-resolution range worked out for you.
Frequently Asked Questions
Can I calculate yarn length from weight?
Yes, if the yarn is uniform and you know what a full skein of it weighs and measures. Divide the weight you have left by the original skein weight, then multiply by the original length. With 37 g left of a 100 g skein labelled 220 yd, that is 37 ÷ 100 = 0.37, and 0.37 × 220 = 81.4 yd.
Do I need a kitchen scale?
Yes, or something with comparable resolution. A kitchen scale reading to 1 g is enough for a typical leftover. A bathroom scale is not — its steps are far too coarse to distinguish a 40 g ball from a 45 g one, and the error carries straight through into the yardage.
Can I use ounces instead of grams?
Yes. The weight unit cancels, because it appears above and below the division line, so the answer is identical either way — provided both weights use the same unit. A 6 oz skein of 315 yd with 2.2 oz left gives 115.5 yd, and the same skein converted to grams gives the same figure.
What if I lost the label?
Use a sample instead. Measure a known length of the leftover, weigh it, and divide to get length per gram; then multiply by the whole remaining weight. 10 yd weighing 4 g is 2.5 yd per gram, so 37 g is about 92.5 yd. Measure as long a sample as you can — the longer it is, the less your scale's resolution matters.
Does fibre type change the formula?
No. The formula is a proportion, and proportions do not care what the yarn is made of. Fibre changes how many yards a gram gives you, but that relationship is already captured by the label figures or by your own sample. What fibre does affect is weighing: damp yarn is heavier than dry yarn of the same length.
Can the estimate be exact?
No. Two of the three inputs are specifications rather than measurements — the band tells you what the product is sold as, not what your particular skein weighed when it was wound — and the third carries whatever your scale can resolve. On the 100 g / 220 yd example, a scale reading to 1 g leaves the answer anywhere in a 2.2 yd span. Plan with the low end of that span, not the middle.
Sources & further reading
- What each figure on a ball band means — where the two label numbers come from.
- Identifying an unlabelled yarn by measurement — for leftovers whose band is long gone.
- Estimating yardage from gauge and dimensions — how to get a requirement when no pattern states one.
Every worked example here is computed and asserted by a script, then read back out of the finished page and checked a second time — none of the arithmetic on this page was typed by hand. That matters on a page whose whole purpose is showing the working. Conversions use the international yard (0.9144 m) and the avoirdupois ounce (28.349523125 g). Where a range is quoted it is derived from a scale resolution stated in that example, half a division either way; it describes that scale, not the reliability of the method. Two things are deliberately absent: any figure for how far a skein may sit from its printed weight or length, and any allowance for moisture. Neither is published by anyone, so both appear here as named reasons the result is approximate and nothing more. This calculation is ordinary proportional arithmetic; it is practitioner convention rather than a standard, and no body publishes a method for it.
Related tools
- Remaining yarn calculator — this method with the units and the range handled for you.
- Wraps per inch calculator — what an unlabelled yarn is, rather than how much of it you have.
- Yarn substitution calculator — topping a short leftover up with something else.