Calculate Time Durations | Sum and Subtract Time

Instantly find the elapsed time between two points or total up multiple work sessions.

💡 Use Cases

Skip the mental math. Whether you are tracking billable hours, planning a workout, or organizing a travel itinerary, this tool handles the base-60 conversions for you.

• Track Billable Hours: Calculate exactly how long you spent on a client project.
• Log Workouts: Sum up intervals and rest periods.
• Plan Itineraries: Map out travel legs across different time zones or days.

📘 Pro Tips

• Calculate the Gap: Use the Time Difference tab to find the duration between two specific times of day.
• Manage Overnight Shifts: Toggle the "Ends next day" box to calculate durations that cross midnight (e.g., 10:00 PM to 6:00 AM).
• Total Multiple Blocks: Use the Sum Durations tab to aggregate various time intervals into a single grand total.
• Simplify Billing: Results automatically display in decimal format (e.g., 2.5 hours), making payroll and invoicing seamless.

🧐 FAQ

Which input formats are supported? You can use "HH:mm" (e.g., 1:30) or enter total minutes (e.g., 90). The tool recognizes both automatically.

Is there a limit to how many hours I can sum? No. Unlike a standard clock that resets every 24 hours, this calculator sums your input indefinitely.

Is my data private? Yes. All calculations are performed locally in your browser. No data is sent to a server or stored externally.

📚 Why do we use Base-60?

We measure time in units of 60 thanks to the ancient Sumerians and Babylonians. They used a sexagesimal (base-60) system because 60 is a "highly composite number." With 12 factors, it is incredibly easy to divide into halves, thirds, quarters, and fifths without resulting in messy fractions—a logic that has survived for over 5,000 years.