Free Time Duration Calculator

The Duration Calculator is a free online tool that adds and subtracts time durations in hours, minutes, and seconds for time tracking and scheduling.

Yes, it is completely free with no registration required. All calculations happen client-side in your browser.

Yes, the Duration Calculator lets you add and subtract multiple time durations to get a total, useful for project tracking and scheduling.

Absolutely. The Time Duration Calculator processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the Time Duration Calculator is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the Time Duration Calculator in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

The Time Duration Calculator uses industry-standard formulas and algorithms to ensure accurate results. However, for critical financial or medical decisions, always consult a qualified professional.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The Time Duration Calculator works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

Decimal hours express a duration as a single number with the minutes written as a fraction of an hour, rather than in hours-and-minutes form. To convert, divide the minutes by 60 and add them to the whole hours: 90 minutes becomes 1.5 hours, 15 minutes becomes 0.25, and 45 minutes becomes 0.75. The format matters because most payroll, billing, and invoicing systems expect decimal hours, not a 1:30 clock value, and entering 1.30 instead of 1.5 is a common timesheet error. This calculator shows every total in decimal hours automatically alongside the regular HH:MM:SS view, so you never have to do the division by hand. Enter your time spans above, then copy the decimal-hours figure straight into your timesheet or invoice.

There are 60 seconds in a minute, 3,600 seconds in an hour, and 86,400 seconds in a day. A week works out to 604,800 seconds. These large multipliers are why a duration can look surprising once it is converted to a single unit: a span that reads as a tidy few hours and minutes turns into thousands of seconds, and a couple of days becomes a six-figure number. Converting in your head is easy to get wrong because each unit uses a different base, 60 for minutes and seconds but 24 for hours. The Convert Units mode in this tool translates any value between milliseconds, seconds, minutes, hours, days, weeks, months, and years instantly. Type a number, choose the units, and read off every equivalent without touching a calculator app.

Real calendar months vary between 28 and 31 days, so there is no single exact number of days in a month. For unit conversions this tool uses an average month of about 30.44 days and a year of 365.25 days, which accounts for leap years by averaging the extra day across four years. That average gives sensible results when you convert a duration measured in seconds or hours into approximate months or years, but it will not match a specific calendar span exactly. If you need the precise number of days between two real dates, including the actual length of each month and any leap day, use the Timestamps mode instead, which calculates from the dates you enter. Switch to that tab whenever exact calendar accuracy matters.

Two time periods overlap during the window that starts at the later of the two start times and ends at the earlier of the two end times. If a meeting runs 9:00 to 11:00 and another runs 10:30 to 12:00, the overlap begins at 10:30 and ends at 11:00, giving 30 minutes of shared time. When the later start falls after the earlier end, the periods do not touch at all and there is no overlap. Working this out by eye is error-prone once the times cross noon or the periods are long. The Overlap mode in this calculator does it for you: enter the two start and end times and it returns whether they intersect and exactly how long the shared window lasts. Open the Overlap tab to compare any two schedules.

Elapsed time is the gap between a start moment and an end moment, found by subtracting the start from the end. The tricky part is spans that cross midnight: if something runs from 22:00 to 06:00, a plain subtraction gives a negative result, so you add a full day to the end before subtracting, giving eight hours. The Timestamps mode handles this automatically, including an optional break you can deduct from the total, and works from actual calendar dates so month lengths and leap years are respected. For recurring weekday schedules with breaks and a weekly target, the Work Hours mode totals your hours and flags overtime. Enter your start and end in the Timestamps tab and the elapsed duration appears instantly in several formats to copy.