Chronometer

Free online tool. All processing is client-side. No signup needed.

How to Use the Chronometer

1. Enter your input values above
2. Results update automatically
3. Copy or download the output

What is a Chronometer?

A Chronometer (precision timer) measures elapsed time with high precision, similar to a stopwatch but designed for longer-duration tracking with session persistence and export capabilities. While a simple stopwatch works for a single event, a chronometer tracks accumulated time across multiple sessions — perfect for tracking billable project hours, study time over weeks, workout minutes per month, or total time spent on any recurring activity. It saves sessions locally so you can stop and resume hours or days later.

How Does It Work?

Start the chronometer to begin tracking. Unlike a stopwatch that resets when stopped, the chronometer accumulates time — each start/stop adds to the running total. Sessions are stored locally (localStorage), so closing the browser doesn't lose your accumulated time. Features: project/task labels for each session, category tagging (work, study, exercise), daily/weekly/monthly summaries, and CSV export for invoicing or reporting. The running display shows total accumulated time this session, today, and all time.

Formula

Session Duration = Stop Time − Start Time\nAccumulated Total = Σ all session durations\nDaily Total = Σ sessions with same calendar date\n\nDisplay Format: HH:MM:SS (hours, minutes, seconds)\n\nBreakdown:\n• Current Session: time since last Start\n• Today: Σ sessions today\n• This Week: Σ sessions Mon-Sun\n• All Time: Σ all recorded sessions\n\nExport: Session, Start, End, Duration, Label, Date\nCSV format for spreadsheet analysis and invoicing

Who Uses This Tool?

• Freelancers tracking billable hours across multiple projects and clients
• Students logging total study hours for exam preparation
• Programmers measuring time spent on different tasks for productivity analysis
• Gym-goers tracking total workout minutes per week
• Anyone wanting to know 'how much time do I actually spend on X?'

Pro Tips

• Label each session as you start (e.g., 'Client X - Landing Page Design'). It takes 3 seconds and makes invoice/analysis much easier later
• Export monthly CSV files for backup and analysis. Cross-reference with project management tools or invoices
• The chronometer accumulates time across browser sessions via localStorage. Clearing browser data will lose the saved time — export regularly
• Combine with the Pomodoro Timer: use the chronometer to track total productive time, and pomodoros to structure individual work sessions

Frequently Asked Questions about Chronometer

Will I lose my time if I close the browser?

No — sessions are saved in localStorage and persist across browser restarts. Current session time is also preserved. However, clearing browser data will delete saved sessions. Export regularly.

How is this different from a stopwatch?

A stopwatch measures one continuous interval and resets when stopped. A chronometer accumulates time across multiple start/stop cycles, days, and sessions — like an odometer for time. Use a stopwatch for a single race; use a chronometer for tracking work hours over weeks.

Free online Chronometer — no signup, 100% client-side processing. All data stays in your browser.