Contraction Timing

If you have had Braxton Hicks or real labor, are the contractions on the dot as far as timing? For example, would consistent contractions every 7-12 minutes be considered timed if they are off by a few minutes each time? (FTM here). I'm just not sure if they were 10 mins exactly if that is an indication of real labor rather than Braxton Hicks. 
Thanks!