The past tense of fit can cause some confusion between whether it is right to use 'fit' or 'fitted'.
First it is important to understand the meaning of fit as a verb because it has three principle uses.
What you use for the past tense of fit depends on whether you are using the general American English derived version or the British English one.
In American English, the standardised usage is fit. However, in British English, there is more division over the use of fit or fitted, though fitted tends to be the version that is preferred or used more often. So this is how it may vary:
"The business suit that I tried on yesterday fit perfectly"
"The business suit that I tried on yesterday fitted perfectly"
It's important though to remember that these are not fixed rules and you may get different people making different choices for the past simple of fit, irrespective of the words history.
These guidelines for the past tense of fit also apply to the past participle used in the perfect tense. So, in American English, there is a preference for fit:
Or in British English:
When you are thinking about the past simple of fit, don't get it mixed up with adjectives where the words can have a different meaning:
But fitted as an adjective is also possible, but this is to indicate something that is designed to fit:
So the general differences between fit and fitted in the past tense are: