Triple conversion

I'm writing a script about people playing a dumb game of trying to see how close they can get to closing a door while still keeping it ajar.

First I wrote "The door is ajar - but only by a couple of inches."

Then I realized I had to write, "The door is ajar - but only by a few centimeters."

Then I realized I had to write, "The door is ajar - but only by a few centimetres."

I overcame jetlag about a year ago. But culturelag is still hanging heavy.