How to time laps and splits with a stopwatch

The short answer

Press Start (or the space bar) when the effort starts and press Lap (or L) every time you pass the end of a lap. Each lap appears in the table with its Lap time and the Total, which is the split. When you finish, press Stop, then copy the table or press Download CSV to open it in a spreadsheet.

From two laps on, the fastest lap is marked in green and the slowest in red, so you can see at a glance where you gained or lost time.

Lap time vs split time

The two terms are often mixed up, and runners in particular use splits loosely for both. Strictly, a lap time measures one segment and a split time is cumulative from the start. Adding up the lap times gives the split at that point, and the difference between two consecutive splits gives the lap time.

Take a 1600 m run on a 400 m track:

• Even pacing: all laps within a second or two of each other. Usually the most efficient way to run a distance.
• Negative split: the second half is faster than the first. In the example the first half took 3:00 and the second 3:04, so this was a positive split.
• Positive split: slowing down, often a sign of starting too fast.

Timing runs, swims and workouts

Running on a track: a standard outdoor track is 400 m in lane 1, so a mile is about four laps plus 9 meters. To run 5 km in 25:00 you need 2:00 per 400 m lap; for 20:00, 1:36 per lap. Press Lap as your chest passes the line you started from, and use the same line every time.

Running on roads: use kilometer or mile markers as lap points. The lap time is then your pace per kilometer or mile, and the total shows whether you are on schedule for a target time.

Swimming: in a 25 m pool, 100 m is four lengths; in a 50 m pool, two. Coaches usually take a split at every 50 m. Press Lap when the swimmer touches the wall, not when they push off.

Interval training: for a session such as 6 × 400 m with 90 seconds of rest, press Lap at the end of each fast interval and again at the end of each rest. Odd laps are your intervals, even laps your rest periods, and the table shows whether the intervals stayed consistent. For circuit workouts, press Lap at the end of each station.

How accurate is hand timing?

The stopwatch calculates time from the system clock and shows hundredths of a second, so the clock itself is not the weak point. The person pressing the button is. A typical simple reaction time to a visual signal is around 0.2 to 0.25 seconds, a little faster to a sound. When you start on a signal and stop on a finish, part of this delay cancels out, but hand times are still commonly off by about a tenth of a second or more, which is why official sprint results use electronic timing.

Where you stand matters too. Sound travels about 343 meters per second, so a timer 100 m from a starting pistol who starts on the bang is about 0.29 seconds late. Start on what you see (the flash, the arm dropping, the first movement) rather than what you hear.

• Use one person for start and stop on the same athlete, so their delay is similar at both ends.
• Anticipate the finish line: watch the athlete approach and press as the torso crosses, rather than reacting after it crosses.
• Practice your reaction: start the stopwatch and try to stop it at exactly 10.00 seconds without looking. Most people land within a tenth or two after some practice.
• Compare lap times from the same timer only. Mixing timers adds their differences to your data.

Exporting and analyzing your laps

After a session, press Copy to put the lap table on the clipboard and paste it into a spreadsheet, a training log or a message to your coach. Download CSV saves a file named laps.csv that opens correctly in Excel and Google Sheets, with the lap number, lap time and total for every lap.

In a spreadsheet you can chart lap times to see fatigue, calculate the average lap and the spread between fastest and slowest, or compare the same workout across weeks. A spread of under 2 percent of the lap time means very even pacing; over 5 percent usually means the start was too fast.

Practical tips

• Use the keyboard on a laptop: space starts and stops, L records a lap while running, R resets when stopped, F switches to full screen.
• Full screen makes the digits readable from a distance, for example on a laptop next to a treadmill or at the side of a pool.
• The stopwatch keeps running if the tab goes to the background or the page reloads, because the start time is saved on your device.
• Record a lap at the end even if the last segment is shorter; the total is still your finish time.
• For timing several athletes at once, one stopwatch per person is far more reliable than one timer pressing Lap for different runners.