Average internal door width – Single door – Arch door – Double door
How to Measure a Door? What is standard door width? : Average Internal Door Width Single Door Arch Door Double Door
Quote from Article entitled How to Measure a Door? What is standard door width?:
This is done at the top and bottom edges. For the standard rectangular door, the width and height edges should be at perfect right angles to each other.
The full version of the article can be found here.