Online Stopwatch Full Screen – Setups, Laps and Splits

Q: Can I use it as a lap timer for karting or a track day?

From the fence, yes. Circuit laps from the fence takes one press for each pass of the line, marks the fastest lap and leaves the standing-start lap out of the mean. From the driving seat you need GPS or a trackside beacon.

How it works

Use this online stopwatch full screen or inside the page. Start and Stop, or the space bar, run the clock. Lap lists each lap beside the total, newest first, so it doubles as a lap timer.

Read the full guide

Start, lap, stop, reset

Press Start the stopwatch or the space bar. Press Lap, or L, as each lap ends. Time is that lap alone. Total (split) is the clock at that press. From three laps on, the fastest and slowest are marked. Stop ends the last lap; one under two seconds is listed but not ranked. Reset, or R, shows only while stopped. It clears the laps, and Undo brings them back. Copy laps pastes into a spreadsheet as columns.

Full screen and setups

Full screen, or F, gives the whole display to the stopwatch. Leave full screen or Esc brings the page back. More options holds 13 setups: the same stopwatch arranged for one job, such as track laps with pace per km or relay legs.

Press on what you see, not on a count: the chest on the line, the hand on the wall.
Stand level with the finish line. From an angle a runner seems to cross early or late.
Your screen may still dim. Set a longer screen timeout first. A dimmed screen never changes the time.

Questions and answers

What is the difference between a lap time and a split time?

A lap time is the time between two presses of Lap. A split is the total on the clock at that press. After laps of 95, 97 and 96 seconds, Time reads 1:35.00, 1:37.00 and 1:36.00, and Total (split) reads 1:35.00, 3:12.00 and 4:48.00.

How accurate is an online stopwatch?

The clock is better than the hand on the button. Most browsers report time in steps of a millisecond or finer, and this page stamps each press with the moment the browser received it. The limit is your reaction at the start and the stop.

Does it keep running if I switch tabs or lock my phone?

Yes. The page stores the moment you pressed Start and works the time out from that, so a hidden tab loses nothing. A reload carries on too: the run is kept in this browser. After a sleep, the page checks the ordinary clock.

Why will it not go full screen on my phone?

On an iPhone the browser does not offer full screen to web pages, although its tablet version does. There the button hides the rest of the page, so the stopwatch takes the whole window. Turn the phone sideways for the largest digits.

Can I use it as a lap timer for karting or a track day?

From the fence, yes. Circuit laps from the fence takes one press for each pass of the line, marks the fastest lap and leaves the standing-start lap out of the mean. From the driving seat you need GPS or a trackside beacon.

All 13 stopwatch setups

Everyday timing 4

Hours, minutes and seconds For anything over an hour: a study block, a long bake, a drive. Hundredths are hidden because they mean nothing at this scale. The time is worked out from the moment you pressed Start, so it stays right while the tab sits in the background.
Plain stopwatch Minutes, seconds and hundredths, with Start, Lap and Reset. Space starts and stops, L marks a lap, and R resets only while the clock is stopped, so a stray key cannot wipe a running time.
Tenths only, rounded up Athletics rules treat a hand time as accurate to a tenth of a second at best, and any hundredths beyond zero go up to the next tenth, so a hand-timed 12.31 is written down as 12.4. This setup does that rounding on every lap and on the stopped time.
Three, two, one, go A three-second lead-in before the clock starts, shown as large digits and with no sound. Press Start, put the phone down and get into position. It is the setup for timing yourself: a plank, a wall sit, a long note on a wind instrument.

Show all 13 stopwatch setups (9 more)

Track, pool and circuit 7

25 m pool lengths with pace per 100 m Press Mark length on every wall touch, and each length is turned into pace per 100 m. A 30-second length is 2:00 per 100 m, and 1,500 m is 60 lengths. In a 50 m pool, halve the pace shown.
400 m track laps with pace per km One press each time the runner crosses the finish line, with pace per kilometre beside every lap: a 96-second lap is 4:00 per km. A 5,000 m race is 12.5 laps and starts at the 200 m mark, so its first row is a half lap. Skip the pace on that row.
Circuit laps from the fence For karts, bikes, radio-controlled cars or a slot-car track. Start the clock as the vehicle crosses the line and press Lap on every pass. The first lap from a standing start is slow, so it is marked as an out lap and left out of fastest, slowest and the mean.
Finish times for a whole field One start, then one press for every runner across the line. The list becomes the finish order with a time for each: 1st, 2nd, 3rd. Have a second person write bib numbers in the same order, and match the two lists afterwards.
Relay legs, four runners Press Mark leg as the baton changes hands, and the fourth press stops the clock. Leg 1 starts from a standstill, while legs 2 to 4 take the baton already running, so compare a runner's leg with their own earlier legs and not with their flat time.
Rowing machine: every 500 m Indoor rowers measure speed as the time needed to cover 500 m. Press Mark 500 m each time the machine's monitor passes another 500 m, and every row is already in that unit. Holding 2:00 for four rows is a 2,000 m piece in 8:00.
Work and rest intervals Each press flips between Work and Rest, and the line under the table gives a mean for each. After 6 × 400 m you can see whether the last rep faded and whether the recoveries crept up.

Talks and exam papers 2

Exam paper by section Press Mark section when you move to the next section of a past paper, and the table shows where the time really went. To plan, divide minutes by marks: a 90-minute paper worth 75 marks allows 1.2 minutes a mark, so a 10-mark question earns 12 minutes.
Talk rehearsal by part Press Mark part each time you move to the next part of the talk. If a 10-minute slot comes out at 11:40 in rehearsal, the Time column shows which part holds the extra 1:40, so you cut there and leave the rest alone.

How this list was compiled: Setups and notes were designed and written for this page. Every worked example (paces, length counts, minutes per mark, the rounded hand time) was computed. Hand times being accurate only to a tenth of a second, with any hundredths beyond zero rounded to the next highest tenth: https://en.wikipedia.org/wiki/Fully_automatic_time. Indoor rowing speed measured as the time to travel 500 m: https://en.wikipedia.org/wiki/Indoor_rower. Browser behaviour described on the page: the monotonic clock and its failure to tick during sleep on some systems, https://developer.mozilla.org/en-US/docs/Web/API/Performance/now; timers cut back in inactive tabs, https://developer.mozilla.org/en-US/docs/Web/API/Window/setTimeout; the Screen Wake Lock API and when a lock is released or refused, https://developer.mozilla.org/en-US/docs/Web/API/Screen_Wake_Lock_API; full-screen mode needing a user action, https://developer.mozilla.org/en-US/docs/Web/API/Element/requestFullscreen, and being available on iPad but not on iPhone, from the api.Element.requestFullscreen entry of https://github.com/mdn/browser-compat-data. All checked 2026-09-19. The 5,000 m start at the 200 m mark follows from the arithmetic: 12.5 laps of a 400 m track that must end at the finish line. Licence: own work