Contraction Calculator

Contraction timing tracks two numbers: how long each contraction lasts and how often they come. Labor contractions tend to get longer, stronger and closer together as labor goes on¹. This tool records the start and end of each contraction, so you can see that pattern without doing the math.

What Contraction Timing Measures

• Duration: how long one contraction lasts, from when the tightening starts to when it fully eases.

• Frequency: how far apart contractions are, counted from the start of one contraction to the start of the next² ³.

Timing shows the pattern of your contractions. It cannot show how far your cervix has opened or confirm labor. Only a check by your midwife or doctor can.

The Formula

Duration = end time of a contraction - its start time

Frequency = start time of a contraction - start time of the one before it

Last-hour average = total of the values from the past 60 minutes ÷ how many there are

Measuring from the end of one contraction to the start of the next is a common mistake. It counts only the rest between them, so contractions look further apart than they are.

How This Calculator Computes Your Result

Start timing once you have had a few contractions in a row². Tap Start contraction when a tightening begins and Stop contraction when it has fully eased. The tool logs the clock time, length and frequency of each one in minutes and seconds. It also shows your last 60 minutes: the number of contractions, average length, average frequency, and the shortest and longest gap. Older contractions stay in your log but drop out of the averages.

A 5-1-1 checklist shows which parts of the rule your last hour meets. You can also enter your weeks of pregnancy (optional). Your times are saved only in this browser on this device, with no account, and Clear all deletes them. Copy summary gives you a short text to read out or send to your midwife or labor unit.

What Your Result Means

The 5-1-1 rule means contractions about 5 minutes apart, each lasting about 1 minute, for 1 hour². Many hospitals use it to tell you when to call or come in, but advice differs. Here is how the tool's messages line up with published guidance:

The NHS suggests calling for guidance once regular contractions come every 5 minutes or more often¹. Your own hospital may give you a different rule, and their instructions come first.

True Labor or Braxton Hicks?

Many people feel mild, practice contractions before labor starts. These are called Braxton Hicks contractions⁴. They tend to be irregular, do not build up, and may stop when you walk, rest or change position¹ ³. True labor contractions keep coming no matter what you do, come at regular times, and get longer and stronger over time³ ⁴. In true labor they are often about 5 to 10 minutes apart and last 30 to 70 seconds⁴. In active labor they are usually 2 to 5 minutes apart and last about 60 to 90 seconds³.

An hour of timing helps you see which pattern you have. If you are still not sure, it is fine to call your care team³.

When to Call Right Away, Whatever the Timing

NHS and NIH guidance says to contact your midwife, doctor or labor unit straight away if¹ ⁴:

• Your waters break or you are leaking fluid.

• You have vaginal bleeding.

• Your baby is moving less than usual.

• You are under 37 weeks and think you might be in labor.

The NHS adds that you should not wait until the next day, even in the middle of the night¹. Before 37 weeks, labor is called preterm labor. Signs include contractions every 10 minutes or more often, and NIH notes that frequent contractions, such as six or more in an hour, are not normal⁵. The 5-1-1 rule is for labor at full term, so this tool does not use it if you enter fewer than 37 weeks.