Contraction Timer
Log the start and end times of up to six contractions and instantly see how long each one lasts, how far apart they are, and whether they match the 5-1-1 labor pattern.
Track Contraction Length and Spacing
Contraction Timer Formula
- \(D_i\) — duration of contraction \(i\), in seconds
- \(E_i\) — end time of contraction \(i\), in seconds since midnight
- \(S_i\) — start time of contraction \(i\), in seconds since midnight
- \(I_i\) — interval between the starts of two consecutive contractions
Using these values, the calculator also runs a 5-1-1 check: contractions arriving about 5 minutes apart (interval \(\le 300\) seconds), lasting about 1 minute (duration \(\ge 45\) seconds). The check uses the last two to three contractions, because recent values show the current trend better than an average over the whole session.
Contraction Timer – Calculation Example
Example: six contractions timed between 20:04 and 20:45.
\[ D_1 = 20{:}04{:}45 - 20{:}04{:}00 = 45 \text{ s} \]
\[ I_1 = 20{:}12{:}30 - 20{:}04{:}00 = 510 \text{ s} = 8 \text{ m } 30 \text{ s} \]
Repeating this for all six contractions gives durations of 45 s, 50 s, 40 s, 60 s, 45 s and 60 s, and intervals of 8 m 30 s, 8 m 30 s, 8 m, 7 m 30 s and 7 m 30 s.
\[ \bar{D}_{\text{all}} = \frac{45+50+40+60+45+60}{6} = 50 \text{ s} \]
\[ \bar{I}_{\text{all}} = \frac{510+510+480+450+450}{5} = 480 \text{ s} = 8 \text{ m} \]
For the last three contractions (60 s, 45 s, 60 s) the average duration is 55 s, and the last two intervals (7 m 30 s each) give a recent average interval of 7 m 30 s.
Result: average duration 50 s, average interval 8 m (all contractions); recent averages 55 s and 7 m 30 s. The contractions are getting closer together but do not yet fit the 5-1-1 pattern — keep timing them.
How to Use the Contraction Timer
- Note the clock time when a contraction begins and when it eases off. A phone stopwatch or a notes app works well.
- Enter the start time in the Contraction 1 — start field and the finish time in Contraction 1 — end, using the 24-hour clock (hh:mm or hh:mm:ss).
- Repeat for each contraction in Contraction 2 through Contraction 6. Leave unused rows blank — the calculator ignores them.
- Check the Contraction log table for each contraction's duration and the gap since the previous one.
- Compare the averages of all contractions with the recent averages (last three), and read the Pattern check (5-1-1 rule) message for guidance.
What the Numbers Mean
A contraction is a wave of tightening in the uterus. Two measurements describe it: duration — how long each tightening lasts, measured from the moment it starts to the moment it fully eases — and interval — the time from the start of one contraction to the start of the next. The interval, not the gap between contractions, is what midwives and doctors usually ask for, because it shows how frequently they are coming.
In early labor, contractions are typically short (20–40 seconds) and irregular, often 10–20 minutes apart or more. As labor progresses they become longer, stronger and closer together. The classic 5-1-1 rule suggests calling your midwife or heading to your birth place when contractions have been coming about every 5 minutes, lasting about 1 minute each, for at least 1 hour. The calculator compares your recent intervals and durations against this pattern automatically.
The recent averages (last three contractions) matter more than the overall averages. If the recent interval is shorter than the overall one, contractions are speeding up — exactly what you want to track as labor advances. A session of six contractions spans roughly 40 minutes, which is why the 5-1-1 check here is a snapshot rather than proof that the pattern has held for a full hour.
Practical Tips and Limitations
- Timing method: count from the very first tightening, through the peak, to the moment the uterus fully relaxes. Ask your birth partner to do the timing so you can focus on breathing.
- Don't stop at six: if you have been timing for more than an hour, use the six most recent contractions to keep the averages current.
- Braxton Hicks: practice contractions are usually irregular, under 45 seconds, and stay the same or fade when you change position or drink water. True labor contractions keep coming regardless.
- Midnight crossing: the calculator handles sessions that span midnight, as long as each contraction's end time is later than its start time.
- Medical situations: contact your care provider right away — regardless of any pattern — if your water breaks, you notice bleeding, the pain is severe and constant, the baby moves noticeably less, or you are before 37 weeks. This tool offers information, not medical advice, and never replaces a phone call to your midwife or doctor.
- Other guidance: some providers use a 4-1-1 rule (4 minutes apart, 1 minute long, 1 hour), especially for first births or long distances to the hospital. Ask at a prenatal appointment which rule applies to you.
While you wait for labor, you may find our Pregnancy Due Date calculator and the Gestational Age (AOG) calculator useful for keeping track of where you are in the pregnancy. After the birth, the Infant Feeding Volume calculator and the Child Development Tracker can help with the next stage.
Frequently Asked Questions
How do I time contractions by hand without a calculator?
Write down the clock time at the very first hint of tightening and again when your belly fully softens — that difference is the duration. Then note the start time of the next contraction; the difference between the two start times is the interval. Do this for at least an hour. Many people mistakenly measure the rest period between contractions instead, which always looks shorter than the interval providers ask for.
What counts as the interval — the gap between contractions or the time from start to start?
The interval is measured from the start of one contraction to the start of the next. So if a contraction begins at 21:00, lasts 60 seconds, and the next begins at 21:05, the interval is 5 minutes even though the pain-free gap was only 4 minutes. Midwives and doctors almost always mean start-to-start, so report it that way. The calculator computes this automatically.
What pattern of contractions means labor is getting close?
Look for three trends at once: contractions getting longer (45–60+ seconds), stronger (harder to talk through), and closer together (moving from 10–15 minutes toward 5 minutes apart). The classic 5-1-1 rule — about 5 minutes apart, 1 minute long, for 1 hour — is the usual signal to call your provider or head to your birth place. Some use 4-1-1 instead; confirm your target at a prenatal visit.
How are Braxton Hicks contractions different from real labor contractions?
Practice contractions are usually irregular in timing, under about 45 seconds, and mild. The telltale test: they ease or disappear when you change position, walk, drink water, or rest. True labor contractions keep coming regardless of what you do, arrive at progressively shorter intervals, and grow in intensity. If your timed contractions jump around — 6 minutes, then 14, then 9 — you are likely still in practice territory.
Why do I get an error when the end time is earlier than the start time?
Each contraction must have an end time later than its start time. The tool handles a session that crosses midnight (for example, a contraction starting at 23:58 and ending at 00:01 counts as 3 minutes), but you cannot enter an end that lands before the start on the clock. Also check for typos like 20:65 or swapping the start and end fields — a contraction lasting several hours almost always means the fields were reversed.
How do I convert my times into minutes and seconds for a birth report?
Divide seconds by 60: 510 seconds is 8 minutes 30 seconds (8 × 60 + 30). For intervals, 5 minutes = 300 seconds and 1 minute = 60 seconds, which is exactly what the 5-1-1 thresholds use. If your notes only show hh:mm, remember the precision is limited to whole minutes — entering hh:mm:ss gives more accurate durations, since a typical contraction lasts well under two minutes.
Is it safe to rely only on the 5-1-1 pattern before calling my provider?
No — the 5-1-1 rule is a general guideline, not a diagnosis, and individual circumstances vary. Contact your midwife or doctor immediately, regardless of any pattern, if your water breaks, you have bleeding, the pain is severe and constant, the baby moves noticeably less, or you are under 37 weeks. Second or later births can progress much faster, so many providers advise calling earlier than 5-1-1. When in doubt, make the call.