Take your actual body measurements as it is more accurate than measuring over your clothes
Measure around the fullest part of your bust and across your shoulder blades
Measure around the natural waist, keeping the tape measure taut.
Stand with your feet together, find the widest part of the hips, usually about 7”/18cm below natural waist, measure around the fullest part of your hips
Stand with your feet together, measure from your natural waist down the side of your legs to your desired length. For floor length, please keep in mide that the accurate measurement depends on whether you are going to wear heels or flats with it. The hem should hit at the middle of the heel shaft or should hit slightly above the flat shoe.