Stopwatch
Use this online stopwatch to measure elapsed time and save lap records. Track study sessions, workout intervals, task time, or experiment timing directly in your browser.
Lap records
No lap records yet.
Press the lap button while running or paused to save a segment time.
Usage Tips
Use lap times when you need to record each segment
Press the lap button when you need to measure total time and segment times together, such as running laps, workout sets, study problem solving, or work steps. You can save each segment without stopping the stopwatch, making it easier to compare pace changes and repeated task times.
What is Stopwatch?
The Stopwatch is a high-precision online timer designed to measure elapsed time down to hundredths of a second (milliseconds). Ideal for physical training, exam preparation, productivity tracking, scientific experiments, and cooking, it enables users to record unlimited lap and split times in real-time. This tool guarantees reliable performance, allowing users to export timing datasets directly to other text-based tools for deep performance analysis.
How to Use
- 1Click the 'Start' button to initiate the real-time stopwatch elapsed counter.
- 2While running, click the 'Lap' button to capture intermediate intervals; this appends segment and split times to a real-time list below the timer.
- 3Click the 'Stop' button to temporarily freeze time measurements and review current interval records.
- 4Click 'Resume' to continue counting from the frozen point, or click 'Reset' to clear the counter to zero and wipe all captured lap history.
- 5Use the copy function to extract your complete lap table dataset directly into spreadsheets, journals, or text editors.
Track elapsed time and segment time together
Last reviewed: July 11, 2026Timestamp-based measurement
elapsed = current timestamp − start timestamp + prior paused time; lap = current split − previous split
The timer uses actual time differences rather than relying only on screen refresh events, so delayed background callbacks do not erase elapsed time.
Recording two segments
- • First split 12.345 seconds
- • Second split 20.000 seconds
- • Compare lap and cumulative split
- 1. First lap = 12.345 seconds
- 2. Second lap = 20.000 − 12.345 = 7.655 seconds
- 3. Split is cumulative from start; lap is the interval since the previous record
The first lap is about 12.35 seconds, the second about 7.66 seconds, and the second split is 20.00 seconds.
How to read the result
- Splits show overall progress, while laps compare the most recent segment or pace change.
- Pause and resume preserve accumulated time for workouts, study sessions, and work tracking.
Conditions that change the result
- Display milliseconds can differ slightly from physical timing hardware because of rendering and operating-system scheduling.
- Official races and sub-millisecond experiments require dedicated timing equipment.
Common input mistakes
- Without a lap record there is no previous segment to compare.
- Confusing pause with reset can make a new measurement start from zero.
Reference Knowledge
- ●Timing Accuracy Architecture: Depending solely on JavaScript's setInterval functions can lead to cumulative timing drift due to CPU cycles. This tool relies on absolute system timestamps, calculating the exact delta between the start event and the render clock to ensure absolute timing integrity.
- ●Background Browser Optimization: Modern browsers systematically throttle background processes to save battery. This stopwatch counter bypasses background lag by evaluating absolute timestamp differences as soon as you refocus the tab, preventing any timing discrepancies.
- ●Lap Time vs. Split Time Concepts: 'Lap Time' measures the elapsed interval since the last lap capture, whereas 'Split Time' measures the total cumulative time from the starting point of the stopwatch. Tracking both is key for analyzing cyclical paces or endurance performance.
- ●Sports-Grade Timing Limits: Web browser runtimes are subject to minor scheduling delays from operating systems and monitor refresh frames. For Olympic-level official competitions or nanosecond scientific calibrations, dedicated hardware timing equipment is recommended.
FAQ
Q.Does timing pause if I navigate to a different browser tab or minimize the window?
No, the stopwatch does not pause. Visual updates might slow down due to background power-saving policies, but as soon as you return to the page, the timer syncs with the system timestamp to calculate the exact elapsed duration. You can safely switch apps without losing track of your workout or study session.
Q.Is there a limit to how many lap records I can store, and do they persist?
You can record a virtually unlimited number of laps. However, because lap data is held temporarily in the browser's memory, refreshing the page or closing the tab will clear all entries. We recommend using the built-in copy function to save your dataset before closing the page.
Q.Why does the millisecond (1/100s) counter sometimes look like it skips numbers?
The internal calculations are processed smoothly in milliseconds, but your display is limited by the monitor's refresh rate (typically 60Hz or 144Hz). The browser skips rendering frames it cannot display in real-time, resulting in minor visual jumps, but this does not affect the mathematical accuracy of your recorded laps.
Q.How does a stopwatch differ from a timer or Pomodoro tool?
A stopwatch is a count-up tool starting at zero, used to measure how long an event takes with sub-interval splits. A timer is a count-down tool starting from a pre-set limit (e.g., a 3-minute egg timer) and triggers an alarm when done. Choose a stopwatch for tracking progress, and a timer or Pomodoro tool for managing fixed-duration constraints.
