A quick way to ballpark the amount of fabric you need is to measure your hips, and divide by 2. Take that number in inches and count out that many repeats of your sett. Then add 3 times that number and add it to the end.
For example; if your hips are 44". 1/2 of that is 22". Count out 22 repeats of your sett.
If your sett is 8" then 8 X 22" = 176".
Then add 3 X 22" = 66"
For a total of 243".
This will be the approxamate amount of fabric for a kilt with each pleat 1" wide at the hips.
It's only a ballpark figure to find out how much fabric you need.
Hope this helps.