Living here in Turkey you have to learn to substitute many things, lol, and here is guide that hopefully will be of some help when you need to substitute yarn in a knitting pattern.
There is a bit of homework involved but, its not difficult and it enables you to make any project your own.
Fisrt of all you need to note the gauge (the number of stitches and rows per inch), that the designer of the pattern you are going to use got when they worked out the pattern. It's necessary if you want your finished project to be the same size as in the pattern. Therefore you will need to find a yarn that allows you to knit at the same gauge.
Most yarn bands will have the information of how many stitches and rows work up on a certain size needle over 4inches (10cm) in either a picture or in words.
Picking the perfect substitute yarn has a lot to do with personal choice as well and once you've chosen your yarn the next question is:
How much should i buy?
On the original pattern you will find the number of balls or skeins , yardage and weight used to complete the project. If you know the yardage you can work it out based on how much yardage is in each ball. If you don't get an exact number buy an extra ball to be on the safe side.
Once you've bought your yarn and before you start your project, take time to knit a gauge swatch. Every knitter is different and even a small variation in the number of stitches can make a big difference in the sizing.
There are lots of new and fun yarns on the market,
DON'T BE AFRAID! EXPLORE.
Here's a joke for you............ Why did the knitter join a dating service?
Because she wanted to get en-gauge-d !
Oh well! i tried lol