HOW TO MEASURE A KILT
Measure Around the 'Waist': The simple, but little known technique is to measure 1-2 inches ABOVE THE NAVEL.
Order smaller: If you're 36.5 inches around your waist order a 36 Size Kilt But If Your Waist Is Measure Around 37 So You Order 38 Waist Kilt This is Perfect For You. As kilts sit at your belly, your belly has a tendency towards elasticity and you're best ordering a tighter fit than a looser one.
Not the same size as your trousers: The kilt is meant to trim your middle and enhance your shape by cinching your midsection. Often, your waist will be larger or smaller than your trousers.