Add or subtract durations, find the time between two clock readings, or convert decimal hours. See the result in days, hours, minutes and seconds, with the working shown.
Approximate totals use ≈ and are rounded to 6 decimal places.
A duration is a length of time, such as 30 hours or 2 days. Enter its parts, choose addition or subtraction, and calculate. Values need not be normalized first: 75 seconds is accepted as 1 minute 15 seconds. All visible numeric fields must be filled; use 0 for a unit you do not need.
For a daytime interval, select Same day. For 22:30 to 01:15, select Next day. An earlier end on the same day produces an error instead of silently assuming an overnight interval. Equal readings mean zero elapsed time on the same day, or 24 hours when Next day is selected.
Convert each duration with total seconds = days × 86,400 + hours × 3,600 + minutes × 60 + seconds. Then add or subtract. For 2 h 45 min + 1 h 30 min, the totals are 9,900 and 5,400 seconds. Their sum is 15,300 seconds, or 4 h 15 min.
For 1 h − 2 h 30 min, calculate 3,600 − 9,000 = −5,400 seconds. This is −1 h 30 min. The negative sign applies to the entire duration, not just its first displayed unit. This represents a difference or shortfall, not a clock reading.
Elapsed seconds = end clock seconds + day offset × 86,400 − start clock seconds. For 22:30 to 01:15 next day: 4,500 + 86,400 − 81,000 = 9,900 seconds, or 2 h 45 min.
Multiply decimal hours by 3,600 to obtain seconds. For 1.75 hours, 1.75 × 3,600 = 6,300 seconds, or 1 h 45 min. Decimal hours are not hours-and-minutes notation: 1.30 hours is 1 h 18 min, not 1 h 30 min.
No. Every day here is exactly 24 hours. This tool compares durations or clock readings without dates, locations, daylight-saving changes or leap seconds. Actual elapsed time between dated events may differ. Do not use clock mode to measure travel across time zones.
You can find the difference between start and end clock times, then use duration subtraction to remove an unpaid break. This is arithmetic only; the calculator does not apply payroll rounding, overtime rules or employment policies.
Duration fields accept nonnegative integers up to 9 digits each. Integer-second calculations use BigInt, preserving exact results. Decimal hours accept up to 12 whole digits and 9 decimal places. They are rounded to the nearest second, with half-second ties away from zero. Rounded decimal totals are labeled with ≈.
Calculation inputs remain in this browser tab and are not sent to a calculation server or stored in a history. Reloading restores the example values. The web server may log ordinary page and asset requests.
We use the standard definitions: 1 minute = 60 seconds, 1 hour = 3,600 seconds, and a duration day = 86,400 seconds. The BIPM SI Brochure documents these time units. Report reproducible errors to infos@web-calculator.net with the inputs, selected mode and expected result.
Related tools: Fraction calculator and Scientific calculator.
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