When you knit a blanket from a pattern, every instruction is given to you: the pattern stitches, the size of the needles and especially the amount of yarn needed to complete the project. When knitters advance in their skills, they often want to forge out on their own and design projects without the aid of printed patterns. This can create some satisfactory results, but working out the details may be confusing. Make sure you have enough yarn to finish your project, but not so much that you have skeins left over.
Write down the length and width of your desired finished blanket size. Multiply the two figures. The result is the amount of square inches in your finished knitted blanket.
Knit a sample swatch that measures 3 by 3 inches. Use the same yarn, needles and stitch that you will use in your blanket pattern. Using the formula above, you know that this swatch is 9 square inches.
Unravel the swatch and measure how many yards of yarn you used to complete it. Divide the number of yards by 9. This will tell you how many yards of yarn you need for 1 square inch of knitted fabric. If the total has a fraction, round up to the nearest whole number. For instance, if you used 30 yards, the answer would be 3.33. Round it up and consider the total 4 yards per square inch.
Multiply the square inches in your finished blanket size by the number of yards per square inch you need. This will give you the total number of yards of yarn needed for your finished project.
Look on the label of your yarn skein. You will see how many yards of yarn are in each skein. Divide the number of total yards needed by the number of yards in a skein. If the number results in a fraction, round up to the nearest whole number. This final number is the amount of skeins of yarn you need to complete your project.
Always buy all the yarn needed to finish a project at the same time. Dye lots are meant to be uniform, but variations do occur. If you buy the same yarn at two different times, you may get a batch that's lighter or darker.