Because I mostly knit baby stuff , I have the patterns written in baby sizes. To transform a baby blanket into an afgan or a big blanket, it is easy to calculate how many stitches to cast on to make a certain size. But then comes the question: how much yarn to buy???
Most of the skeins have the weight on them, so my calculations are based on this.
Well, my dears, this is when we need a bit of math … oh, no! don’t run away! I promise that is quite simple.
I am using the metric measurements, but even if you use the imperial, the logic is the same.
What do we need? A scale. An electronic one, is more accurate, so, it is better.
Don’t forget that the calculations are more for orientation, but this is what I use.
First knit your swatch. Mine was 15 x 8 cm and was weighing 8 grams.
The area of the swatch is: 15*8cm = 120 square cm
If 120 sq cm weighs 8 grams
Then 100 sq cm weigh…”z” grams
“z” = 100*8 / 120 = 6.66 grams per 100 square centimeters
This means that an area of 100sq cm will weigh about 6.7 grams. (Aproximatelly)
Let’s say I want to knit an 100cm x 150 cm afghan.
It will have an area of: 100*150 = 15000 sq cm.
Quantity of yarn: aprox 6.7 g * 150 = 1005 grams (We multiply with 150 because 6.7 grams are for 100 sq cm)
That will be 10 skeins of 100 grams each. OR 5 skeins of 200 grams each. or what ever yarn you decide to use.
Let’s say I want to knit a 75*110 cm crib blanket
Area: 110*75 = 8250 sq cm
Quantity of yarn: 6.7 g * 82.5 = 552.75 grams
That will be almost 6 skeins of 100 g each
Or 11 skeins of 50 grams each
I am so curious of what you think of this. Do you fond it helpful? What did you used it on (if you did)