In the US, doors are sold in inches. If you are measuring the door in order to bring in some furniture, any measurement of length - inches or centimeters - will work. It is in centimeters. That is more appropriate
The "correct unit of measure" is the one you choose. See the list below for suggestions:cupspintsquartsgallonsmilliliterscentilitersdeciliterslitersThe list is not comprehensive, but should serve.
Miles
After you measure the width of the door, you can use any unit of length you like to describe it. No unit is 'correct' or incorrect, but there's always one that produces the most convenient number ... the number that's easiest to write down, remember, and tell other people about. For the width of a door, I think inches would be a bit more convenient than feet.
meters If you want to be precise in your measurements, you would probably use centimeters. 1 centimeter equals approximately .3937 inches.
A door is about 2 meters, but most likely you'd measure in centimeters.
inch
The unit you should use to measure the thin edge of a dime would be millimeters.
foot
foot
Newtons.
If the mailbox is in front of your house you probably want to use feet (assuming you are in the USA) If it is at the post office you should probably use miles, lol :)
Meters if you're using the metric system. Otherwise use feet.
inches or centimeters
kilograms
millimetres or centimetres.
Centimetre.