Finding a comfortable suit jacket
For a proper fit, your suit jacket should cover your rear and sit flat on your back. Make sure it isn't puckering or pulling.
The jacket’s sleeves should end at your wrist, and your shirt sleeves should stick out another half an inch to quarter inch.
The jacket’s shoulders should fit your shoulders rather than squeeze too tightly or, alternatively, stick out.
Make sure you can move comfortably in your jacket and that your arms have a wide range of motion.