This the methods you should use when taking measurements for garments.
Collar size / A measuring tape around the base of your neck with your index finger just inside the tape. This measurement will allow for sizing ( shrinkage after three to four warm washings ) of a collar.
Yoke / The length of the shoulder panel from seam to seam.
Sleeve length / Half the yoke measurement plus the length of the sleeve. A good measurement would be measured to about one inch above the fist knuckle of the pinky finger.
Tail length / From the front of the yolk where it meets the collar to the bottom of the shirt. Some measure from the back of the collar where it meets the yolk to the bottom of the shirt
Chest measurement / Measured flat from pit to pit or measured across from the third button from the top collar button.
Waist measurement / Measured flat across at the seventh button from the top collar button.
Underarm Measurement / A measuring tape around your chest over the highest part of your chest should give you a chest size,
Jacket length / From the bottom of the collar to the bottom of the coat. 29 1/2" = Short, 30 1/2" = Regular, 31 1/2" = Long. Note: Not all jacket lengths are equal due to fashion statements.
Sleeve length / Inseam measurement from where sleeve joins jacket to end of sleeve. End of sleeve usually is 4 1/4" from tip of thumb.
Chest measurement / Measured flat from Pit seam to Pit seam.
Sleeve measurement / Measured from Pit seam to end of sleeve. End of sleeve usually is 3 3/4" from tip of thumb.
I won't go into trouser fitting for it gets complicated with various rises ( Crotch to top of waist band )
This should act as a guide to help you understand your size requirements and to read other web site size guides. It wouldn't be a bad idea to go to your local Menswear shop and ask them to take your measurements, write them down and keep them with you when you shop in store or online.
If anyone needs any more information, please feel free to contact me.
Happy New Year!