Jacket
Measure around the fullest part of the chest with the tape level. The jacket shoulder seam should sit near the edge of your shoulder. Check that you can button the jacket without pulling across the front.
Trousers
Measure around the waist where you usually wear dress trousers. To check the inseam, lay a well-fitting pair flat and measure along the inside seam from the crotch to the hem.
Shirt
Measure around the base of the neck and compare it with the shirt size guide. Check sleeve length against a shirt that fits you.
Use the measurements listed for the specific garment. If you are between sizes, contact Sina with the item name and your measurements.