How to Check the Measurement
Find a jacket to measure, which suit you well. NOT MEASURE YOUR BODY.
1. Measure the CHEST.
Put the jacket on the table. Make it flat, now you can measure the it. From armpit to armpit.
Tight your tape ruler, to make the measurement correct.
2. To measure the sleeve. The sleeve isn't straight. It's curve. So, please measure it like below drawing.
3. To measure the shoulder.
Don't measure in straight. It's also curve. Please measure like drawing.