Planning basics

Should I buy extra yarn? When one spare ball is worth it

Buy one spare ball of the main colour, from the same dye lot, when your pattern’s quantity is tight. If the designer’s figure is already a whole number of balls, you don’t need anything extra. The spare is there because a ball bought later may come from a different dye lot and look slightly different. The UK shops we checked take unopened balls back within 28 days to three months.

HazelLoop planning guide · Updated 12 October 2026 · Figures from cited sources

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Is the quantity ‘to buy’ or ‘used’?

Look at how the designer writes it. A whole number of balls of a named yarn is a buying figure. Attic24’s Cosy Stripe says 15 × 100 g balls of Stylecraft Special DK, and that ‘these 15 balls are enough’ for about 120 × 180 cm. Sarah Maker’s granny-square blanket lists 7 skeins, about 1,750 yards. Whatever is left in the last ball of each colour is already your margin.

A length in metres or yards is different. B.Hooked’s classic granny blanket gives 400, 500, 400 and 260 yards per colour for the baby size, and about 70 yards per square. You turn that into balls yourself, and the rounding decides how much is left over.

How to tell if the quantity is tight

Divide the pattern length by the metres in one ball and look at what’s after the decimal point. A pattern needing 1,200 m of Stylecraft Special Aran (196 m a ball) works out at 6.12 balls. You buy 7 and have 172 m to spare, more than 14% over. That’s plenty, so skip the extra ball.

Now take 1,150 m. That’s 5.87 balls, so you buy 6 and have only 26 m spare, about 2%. A slightly looser tension or a bigger border would use that up. This is when one more ball of the main colour is worth buying. As a rule of thumb, we buy a spare when the rounding leaves less than a quarter of a ball.

Dye lots: why a later ball can look different

A dye lot is a batch of yarn dyed together. Wool Warehouse puts it simply: ‘batches of yarn that are dyed in the same vat at the same time’. Variations can come from the amount of dye, the water temperature and the fibre itself, so two balls of the same shade from different lots can differ slightly.

Many labels print the dye lot number as well as the shade code. Wool Warehouse shows which lots it has in stock in a drop-down on the product page. Buy all of one colour in one order, and check that the lot numbers match when the parcel arrives. A different lot matters most in large blocks of colour. In a scrappy or striped blanket you may never notice.

Returning a spare ball you didn’t use

Unopened balls can usually go back. On 1 October 2026, Wool Warehouse accepted returns up to 60 days after receipt, for unopened balls in resaleable condition. LoveCrafts took back new, unused products within 30 days of delivery, but not yarn wound into a ball or part of a colour pack. Hobbycraft allowed 28 days for unused items in original packaging, with free returns. Hobbii allowed three months, but you pay postage back to Denmark.

Keep the band on and the ball in its bag. Posting one ball back can cost nearly as much as the ball, so a spare is often more useful kept for the next project in the same yarn.

Adding a percentage in our planner

The planner starts at 0% extra, so it never adds a margin you didn’t ask for. If you add one, it goes on the full pattern length first, then your stash is taken off, then the rest is rounded up to whole balls. For a 600 m pattern with 10% extra and 180 m already in your stash, the new yarn has to cover 480 m. At 196 m a ball, that’s 3 balls.

A percentage doesn’t always change the list. Ten per cent on 1,200 m makes 1,320 m, which still rounds to 7 balls of 196 m. A spare ball fixes a tight figure more simply than a percentage does.

Do you need a spare ball? Stylecraft Special Aran, 196 m per ball
Pattern says	Balls to buy	Left over after rounding	Spare ball?
15 × 100 g balls (whole balls, as Attic24 lists)	15	Already in the designer’s figure	No
1,200 m	7 (6.12 rounded up)	172 m, about 14%	No
1,150 m	6 (5.87 rounded up)	26 m, about 2%	Yes, one of the main colour
980 m	5 (exactly 5.00)	0 m	Yes, one of the main colour

Download this table (CSV) · free to reuse with a link to HazelLoop

Check before you move on

Pattern quantity read as balls to buy or as a length
Length divided by metres per ball, with the decimal checked
One spare of the main colour if less than a quarter of a ball is left over
All balls of each colour bought in one order
Dye lot numbers checked against each other when the parcel arrives
Spare kept unopened, with its band, until the project is finished

Try it with your own numbers.

Calculate whole balls or packs for every colour. Subtract your stash and add UK delivery.

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Common questions

Should I add 10% extra yarn?

Not by default. Check how much the whole-ball rounding already leaves over. If it’s less than a quarter of a ball, buy one more ball of the main colour instead of adding a percentage.

Does the spare need to be the same dye lot?

Yes, that’s the point of buying it now. A ball from a later batch can be a slightly different shade, which shows most in large areas of one colour.

Can I return unopened yarn?

At the shops we checked on 1 October 2026, yes: Wool Warehouse within 60 days, LoveCrafts within 30 days of delivery, Hobbycraft within 28 days and Hobbii within three months. Each has conditions, so read the policy before you order.

Do I need a spare for every colour?

Usually only for the main colour or any colour that covers a large area. Small accent colours rarely run out, and a different dye lot is hard to spot in a small patch.

Sources and scope

Sources checked 1 October 2026. Label facts come from the linked references; worked purchase examples and arithmetic are our own illustrations. Original pattern and product names retain their source spelling.

How much yarn do I need? All UK wool quantity guides

Keep planning

These are planning estimates, not claims of projects we have made. Read our method and editorial approach.