How Much Yarn Do I Need

Every page that answers this question with one number is guessing on your behalf. The honest version takes two minutes longer and does not leave you three skeins short in a discontinued dye lot.

The method, in three steps

1. Work out the finished area. Width in inches, times length in inches. A 50 x 60in throw is 3,000 square inches. The table below has the common sizes already multiplied out.
2. Measure your own yards per square inch. Make a swatch at the gauge and stitch you will actually use, at least 4 x 4in. Note the yardage you used - either measure the yarn before you start, or weigh the swatch and convert using the skein's published yards per gram. Divide yards used by swatch area in square inches.
3. Multiply, then add a margin. Area times yards per square inch gives the working figure. Add 10 percent for a plain piece, 15 to 20 percent if there is a border, seaming, colorwork or fringe.

Finished area for common blanket sizes

Blanket sizes are conventionally set from the mattress they cover, plus overhang. The mattress dimensions below are the standard US sizes; the blanket dimensions are the mattress plus a typical drop, and the area column is simply width times length.

The jump matters. A king coverlet is 3.2 times the area of a 50 x 60in throw. If a pattern's yardage was written for a throw and you are sizing up to a king, you need more than three times the yarn - not a skein or two extra.

Yards per skein for the yarns people actually use

Once you have a yardage figure, this converts it into a shopping list. All figures are the manufacturers' published yardage.

Look at the two chenille yarns. Bernat Blanket gives you 108 yards a ball. A 50 x 60in throw in super bulky needs a lot of balls, and the yarn is bulky enough that the ball count surprises people every time. This is the single most common cause of a half-finished chenille blanket in a cupboard.

Worked example

Say you are making a 50 x 60in throw in worsted weight, single crochet, and your 4 x 4in swatch used 22 yards.

1. Swatch area = 4 x 4 = 16 square inches. Yards per square inch = 22 / 16 = 1.375.
2. Blanket area = 50 x 60 = 3,000 square inches.
3. Yarn needed = 3,000 x 1.375 = 4,125 yards.
4. Add 10 percent for the border and ends = about 4,540 yards.
5. In Red Heart Super Saver at 364 yards a skein: 4,540 / 364 = 12.5 skeins, so buy 13.

Change one input and watch it move: the same blanket in double crochet rather than single crochet typically uses noticeably less yarn for the same area, because taller stitches cover more ground per yard. That is exactly why one published number cannot serve everybody.

Rules of thumb that are actually safe

• Buy all your yarn at once, in one dye lot. Running short mid-project is the expensive failure, not over-buying by one skein.
• Round up to a whole skein, always. A partial skein is a swatch, a repair, or the start of the next thing.
• Weigh, do not guess, when you are close. A kitchen scale plus the skein's published yards-per-gram turns any remnant into an exact yardage.
• Yardage scales with area, not with the longest side. Doubling both dimensions quadruples the yarn.

If you are substituting a different yarn from the one in the pattern, run the numbers through how to substitute yarn first - the yardage changes as soon as the weight or the fiber does. And if you have not chosen the yarn yet, best yarn for a blanket and best yarn for a baby blanket are the places to start.