Use a flexible measuring tape
Measure over a thin shirt
Keep the tape snug, not tight
Stand naturally with arms relaxed
Record all measurements in inches or centimeters
Measure neck around the base where a collar sits
Measure chest around the fullest part, under the arms
Measure waist around the natural waistline
Measure hips around the fullest part of the seat
Measure shoulder width from shoulder point to shoulder point across the back
Measure sleeve length from shoulder point to wrist bone
Measure inseam from crotch to desired trouser length
Measure outseam from waist to ankle if needed
Measure rise from crotch to waistband if needed
Measure thigh around the fullest part of the upper leg
Measure knee around the knee area if needed
Measure cuff opening if needed
Measure jacket length from the base of the neck to the desired hem
Double-check every measurement
Keep the tape level all the way around
Have someone help for more accurate results