When the interval stays at or near 5 minites, and they stay near a minute long. Its may not be a constant 5 minutes, because it can be off by minute give or take. Same with the length of contractions. If you have contractions, feels like your bum is falling of, and you start feelinf pressure galore. Then it will be time.

When you have 5 contractions that each last a minute, in one hour.

5min