Online stopwatch
Press Start, then Lap at each split: every lap and the total show to the hundredth. 1:30.50 = 90.5 seconds.
- Checked on thousands of cases
- Updated November 6, 2026
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Test yourself: every answer is computed by the tool, and the wrong choices are the most common traps.
How it works
Formula: Lap = split − previous split
The stopwatch notes the moment it starts and shows the gap with your device's clock, to the hundredth of a second (cut off, so it never runs ahead). Each press on Lap records a split time; a lap time is the difference between two splits. The best and slowest laps are marked from two laps on.
Worked examples
1:30.50
1 minute, 30 seconds and 50 hundredths = 90.5 s.
0:09.58
9.58 seconds.
Splits at 1:02.40 and 2:04.10
The 2nd lap took 1:01.70.
Common mistakes
Reading 1:30.50 as 130.5 seconds.
A minute is 60 seconds: 90.5 s.
Reading 0:01.05 as 1.5 seconds.
The two digits after the point are hundredths: 1.05 s.
Adding up the Total column to get the total time.
Total is already cumulative: it is the lap times that add up.
What the calculation leaves out
- Starting and stopping by hand adds your reaction time: the hundredths shown are finer than the tap.
- The time comes from your device's clock: if it is reset during the timing, the result can be off.
Reading a stopwatch time
| Display | In seconds |
|---|---|
| 0:09.58 | 9.58 s |
| 0:59.99 | 59.99 s |
| 1:30.50 | 90.5 s |
| 12:05.00 | 725 s |
| 1:02:03.40 | 3,723.4 s |
Frequently asked questions
Does the stopwatch keep going if I switch tabs?
Yes: the time is worked out from your device's clock, not counted second by second.
How do I read 1:30.50?
1 minute, 30 seconds and 50 hundredths, or 90.5 seconds.
Can I use it for an official race?
No: starting and stopping by hand adds the person's reaction time. Races use electronic timing.