⏱ Stopwatch

A free online stopwatch with start, pause, resume, reset, and lap time tracking — accurate to the hundredth of a second.

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Guide

About the Online Stopwatch

Last updated: July 2026 · Reviewed by the NeftCal editorial team

This free online stopwatch runs entirely in your browser — click Start and it counts up in hours, minutes, seconds and hundredths of a second, with Pause, Resume, Lap, and Reset controls, no app download or signup required.

What This Stopwatch Does

Click Start to begin timing. The display updates continuously, showing elapsed time down to the hundredth of a second. Click Lap at any point to record a split without stopping the clock — each lap shows both its individual split time and the cumulative total. Click Pause to freeze the timer, Start again to resume exactly where you left off, or Reset to zero everything out and clear the lap list.

Who Should Use This Stopwatch

Runners and athletes timing intervals or laps, cooks and bakers timing steps in a recipe, students timing study sessions or presentations, teachers timing classroom activities, and anyone who just needs a quick, reliable stopwatch without installing an app.

Real-World Applications

  • Interval training and lap timing for running, swimming, or cycling
  • Timing cooking or baking steps precisely
  • Presentation and public-speaking practice timing
  • Board game or trivia turn timers
  • Pairing with NeftCal's Pace Calculator to convert lap times into running pace
How It Works

How the Stopwatch Keeps Accurate Time

The logic behind the running display and lap calculations

Elapsed Time
Elapsed = Current Timestamp − Start Timestamp + Previously Accumulated Time (if resumed after a pause)

Lap Split Time
Split Time = Current Elapsed Time − Previous Lap's Elapsed Time

Display Formatting
Hours = ⌊Elapsed ÷ 3,600,000⌋, Minutes = ⌊(Elapsed mod 3,600,000) ÷ 60,000⌋, Seconds = ⌊(Elapsed mod 60,000) ÷ 1,000⌋, Hundredths = ⌊(Elapsed mod 1,000) ÷ 10⌋
🎯

Timestamp-Based, Not Tick-Counted

Rather than incrementing a counter every interval (which can drift), the stopwatch recalculates elapsed time from a fixed start timestamp every frame, so brief delays from a busy tab don't cause the total to fall behind.

⏸️

Pause & Resume

Pausing stores the elapsed time so far. Resuming sets a new start timestamp offset by that stored value, so the display continues seamlessly rather than restarting from zero.

🏁

Fastest/Slowest Lap Highlighting

Once at least two laps are recorded, the calculator compares all split times and highlights the shortest in green and the longest in red for quick visual feedback.

⚙️ Why Timestamp-Based Timing

Using the browser's high-resolution clock and computing elapsed time as a difference (rather than counting "+10ms" on every tick) avoids compounding rounding errors and keeps the display accurate even if a tick is occasionally delayed by the browser.

🎯 When to Use Lap vs. Reset

  • Lap — record a split without stopping the overall clock
  • Pause — temporarily freeze the clock, then resume it later
  • Reset — clear everything and start completely over

📋 Assumptions

  • The browser tab stays open for the stopwatch to keep running
  • Your device's clock and browser timer are functioning normally

⚠️ Limitations

  • Closing or refreshing the tab resets the stopwatch and clears all laps
  • Not certified for official athletic competition timing
  • Extremely long-running sessions (many hours) are supported but uncommon
Walkthrough

Step-by-Step: How to Use the Stopwatch

From starting the clock to reviewing your laps

Click "Start"

Begin timing — the display starts counting up in hours, minutes, seconds and hundredths.

Click "Lap" to record splits

Record intermediate times without stopping the clock — each lap shows its split and cumulative total.

Click "Pause" to stop temporarily

Freeze the elapsed time without losing it.

Click "Start" again to resume

Continue timing from exactly where you paused.

Click "Reset" to clear everything

Zero out the timer and clear all recorded laps to start fresh.

Use Cases

Practical Use Cases for a Stopwatch

Where precise, lap-tracked timing comes in handy

🏃

Running & interval training

Time laps around a track or intervals during a workout, then compare splits.

🍳

Cooking & baking

Time individual steps in a recipe precisely, from proofing dough to searing a steak.

🎤

Presentation practice

Time a speech or presentation run-through to stay within a target length.

🎲

Board games & trivia

Time turns or rounds for games that use a time limit.

🧑‍🔬

Simple lab or classroom timing

Time reactions, experiments, or classroom activities without dedicated equipment.

🧘

Focus & study sessions

Track how long a focused work or study session actually lasted.

Pros & Cons

Advantages and Limitations

What this stopwatch does well, and where it has boundaries

✅ Advantages

  • Free, instant, and requires no signup or app download
  • Runs entirely in your browser — no data is sent to a server
  • Accurate to the hundredth of a second
  • Full lap tracking with split and cumulative total times
  • Automatically highlights your fastest and slowest lap
  • Works on desktop, tablet, and mobile browsers

⚠️ Limitations

  • Closing or refreshing the tab resets the stopwatch and clears laps
  • Not certified for official athletic competition timing
  • No cloud sync or history across devices or sessions
📝

Summary: This free online stopwatch offers start, pause, resume, reset, and full lap tracking accurate to the hundredth of a second — entirely client-side, with no signup. Pair it with the Pace Calculator to turn your lap times into a running pace.

FAQ

Frequently Asked Questions

Common questions about the online stopwatch

How accurate is this online stopwatch?
The stopwatch displays time to the hundredth of a second (centiseconds) and updates using your browser's high-resolution timer, which is accurate for casual timing purposes like workouts, cooking, or games. For scientific or competitive timing, use certified timing equipment.
How do lap times work?
Click Lap while the stopwatch is running to record the current elapsed time as a lap. Each lap entry shows both its split time (time since the previous lap) and its cumulative total time, with the most recent lap listed first.
Can I pause and resume the stopwatch?
Yes. Click Pause to stop the timer without losing the elapsed time, then click Start again to resume from exactly where you left off.
Does the stopwatch keep running if I switch browser tabs?
Yes. The stopwatch calculates elapsed time from a fixed start timestamp rather than counting up tick by tick, so switching tabs or briefly backgrounding the browser doesn't cause it to lose time — the display simply catches up when you return.
Will the stopwatch keep running if I close the tab or refresh the page?
No. Closing the tab or refreshing the page resets the stopwatch, since it runs entirely in your browser's memory with nothing saved to a server.
Can I see my fastest and slowest lap?
Yes. Once you've recorded at least two laps, the fastest split is highlighted in green and the slowest in red in the lap list, making it easy to spot your best and worst intervals at a glance.
Is my stopwatch data saved or sent to a server?
No. This stopwatch runs entirely in your browser — no timing data is transmitted to or stored on a server, and everything resets when you refresh the page.

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