Our Kilts are a Standard/Average 24inch Drop, (about 61cm), we use gradient standards to match this size appropriately for all sizes.
For the vast majority of sizes/heights, this is an appropriate average length. For example, I am 6ft3, and I find this length is fine, during our recent photo-shoot we had models around 5.5ft and this length was still without issue (obviously this may vary as everybody is different and has different length bodies, even those who are the same height), you may also have your own preferences.
If it is of concern, measuring up for drop length is super easy! Simply just measure from your Waist (or if you wear your kilt on your belly measure from here), then measure to the middle of your knee. Alternatively, you might find it easier to kneel on the floor, and measure from your Waist/Belly to the floor, this is your drop length.
Generally speaking, in several years of selling kilts, we have not had a single customer with an issue with our standard drop length, so lets hope that trend continues!