Time Calculator

Free Online Time Calculator

This time calculator handles every common time-math task in one tool. Use Time between to find the duration between any two date-times. Use Add / subtract to add or subtract hours, minutes, and seconds from a starting time. Use Sum durations to total a list of times — perfect for timesheets, workouts, video lengths, or any time-tracking task. Everything runs live in your browser.

How to Use Each Mode

1. Time between two date-times

Pick a start date and time and an end date and time. The tool shows the difference in days, hours, minutes, and seconds, plus the total in plain seconds, minutes, and hours. Useful for project hours, age between two dates, event durations, and shift lengths.

2. Add or subtract from a time

Enter a starting time, choose add or subtract, and specify how many hours, minutes, and seconds to apply. The result is the new time on the 24-hour clock — wraps around midnight automatically if it crosses.

3. Sum a list of durations

Paste one duration per line in HH:MM:SS or HH:MM format. The tool totals them and shows the grand total in hours and minutes. Ideal for adding up a week of timesheet entries, a playlist of video lengths, or training session times.

Where a Time Calculator Helps

• Timesheets and payroll — total a week of clock-in/clock-out times
• Project planning — work out how long a sprint or milestone took
• Workout tracking — sum interval, lap, and total session times
• Video editing — total clip lengths to plan a final cut
• Scheduling — find what time a meeting will end after a given duration
• Cooking — work out start time for a recipe with several timed stages
• Studying — track total time spent on each subject across the week

Format Tips

• Times use the 24-hour clock (00:00 to 23:59) for unambiguous input
• Durations accept both HH:MM:SS and HH:MM — the calculator handles both
• Negative durations are shown when the end time is earlier than the start (with a − sign)
• The total in the sum mode caps at hundreds of hours, so weekly and monthly logs are no problem

Frequently Asked Questions

Does the calculator handle overnight shifts?

Yes. In the "Time between" mode, pick the next-day date for the end. In the "Add / subtract" mode, results that cross midnight wrap to the next day's time automatically.

Can I paste times in 12-hour format with AM/PM?

The input fields use the 24-hour clock to avoid ambiguity. Convert any AM/PM time to 24-hour first (1 PM = 13:00, 11 PM = 23:00, midnight = 00:00).

Is anything sent to a server?

No. All calculations happen in your browser. Times and dates you enter never leave your device — the tool is 100% private and free.

What is the maximum duration I can sum?

Effectively unlimited within any practical use case. The tool handles thousands of entries totalling thousands of hours without precision loss.