Do not GUESS on measuring for a kilt. Once you measure, DO NOT add sizes to your measurement. Order the size you measure. That way you know you will get the right one to fit you.
How to measure for a kilt with out measuring the waist.
Use this when giving a gift or other situation where you are not able to measure their waist.
When you are measuring a pair of pants to determine sizing, it should be around 3-4 inches bigger than what the jeans size says (some sizes closer to 30 are only 2 inches bigger). You should only use this option as a last resort if personally measuring the person is not possible. DO NOT USE THIS OPTION IF YOU CAN MEASURE YOURSELF. Save yourself the time and just do it right the first time!
If for some reason you are just not able to measure anything, you can make a good guess at which size they would need. I would go up two sizes if guessing, i.e. 40 will go to a 44 size kilt. This is only a guess and does not replace at least trying to measure if possible.