How to Measure Your Doors
The best and easiest way to measure your door is to
Open the door
Then place your tape on one edge making sure it stays in place (you could get someone to help with this)
Carry the other end of the tape to the other edge of the door
Finally take a reading from the tape
Taking a reading is easy, you can either take the reading in..
Inches
Centimetres
Millimetres
As you can see in the picture it reads 30 inches, 76.2 centimetres and 762 milimetres.
If you can't measure the door you can measure the frame, its the same principle but you just measure where the door sits in the frame. From where the hinges are to the keep plate for the latch is.