Guide for absolute measurement.
The Perfect Fit
Lot of men suffer a problem to find the perfect fir for their body type. So here's all you need to know about the perfect fir, no matter what your body type is, just follow the guide and get that perfect fit for yourself.
While your blazer is buttoned, make sure you should be able to place your hand flat between your blazer by the buttons. The blazer should be tight when you clench your hand. The length of the arms should be enough so that your shirt is visible by 1 inch approximately while standing by your arms downside.The shirt length should be till your wrist bone, which means your blazer's arm length should end 4 cm from your wrist. The blazer's length should be covering your rear or bottom. The blazer should reach the mid section of your thumb when standing straight while arms facing downwards by your side. The shoulders should be not too big and not too tight.
You don't necessarily need a belt to keep your pants up, it should fit just right. But, make sure your pants aren't too tight. It should cover the heel of your formal oxford shoes.
How exactly you should button you suit:
I've mentioned how to button your blazer while standing in my previous article. Basically it makes your waist look slimmer with broad shoulder, apparently a more masculine look with good physique.
Now the reason why you should always unbutton your blazer while sitting down is that the blazer should be tight at the waist to make your shoulders look wide and waist slim. While sitting it would exert pressure on the buttons and over the time they'll get loose and also might fall off or tear the blazer.
I hope this article helps you to find that perfect fit for your suit.