Time Calculator
Add & subtract time
To add or subtract time, combine hours, minutes and seconds on a 24-hour clock. Enter a start time and a duration to add or subtract — or add two durations together — and this calculator returns the result, noting any day change when the answer crosses midnight.
Time Calculator
Add or subtract h:m:s
Add and subtract time
The time calculator does two kinds of time arithmetic. It can add or subtract a duration from a clock time — for example, what time is it 3 hours 45 minutes after 21:30 — and it can add or subtract two durations to give a total in hours, minutes and seconds. When a clock-time result crosses midnight, it tells you how many days forward or back it lands.
It's the tool for shift planning, cooking and interval timing, working out finish times, or totalling several stretches of time without reaching for a spreadsheet.
Clock time versus duration
A clock time is a point in the day (like 14:00); a duration is a length of time (like 2h 30m). This calculator keeps the two separate: use the first mode when you're moving a time of day, and the second when you're totalling lengths of time.
Related tools
For time spanning specific dates, the hours & duration calculator measures the gap between two date-times. For whole-day maths, use the date difference and date ± days calculators.
Common questions
How do I add hours and minutes to a time?
Can it add two durations together?
What happens when the result passes midnight?
Does it handle seconds?
- Method: hours-minutes-seconds arithmetic on a 24-hour clock, with a day carry when a result crosses midnight.
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