Lay the dress flat on a smooth surface
Smooth out wrinkles without stretching the fabric
Measure the bust across the widest part of the chest
Measure the waist at the narrowest point
Measure the hips across the fullest part
Measure the shoulder width from seam to seam
Measure the sleeve length from shoulder seam to cuff
Measure the dress length from the highest shoulder point to the hem
Measure the neckline if needed
Measure the armhole if needed
Compare all measurements to a size chart
Repeat each measurement for accuracy