As noted in a comment discussion to Is “spaced by 1 meter” correct English:
A: "[if] you are measuring in SI units and not using the size of your gas or electric meter as a unit of length, then the word is METRE [rather than METER]."
B: "Metre vs meter is British English vs American English"
C: "I don't see any evidence that metre is the "international standard""
The suggestion above, is that "Meter" is simply the AmE spelling and "Metre" is the BrE spelling. However, comment A and C conflict – about whether there is or is not an international standard which defines the SI term.
In what contexts should the spelling "Meter" be preferred, and in which contexts should "Metre" be preferred?
Best Answer
In UK English there is a distinct difference between metre & meter.
Metre is a unit of length.
Meter is a 'measuring device' such as a gas or electricity meter.
To torture the linked question somewhat:
Further example
In US English the two equate to the same thing. One is merely a 'foreign spelling' of the other.
You would have to take the meaning from context.