Time duration calculator
Duration between two times, or a time shifted by a duration.
Fill in the fields and the result will appear here automatically.
Works out how long it is between two times, or what time it becomes after adding or subtracting a duration. Times that cross midnight are handled as a normal case rather than an error.
How it works
Formula and logic
Difference mode calculates end minus start around a 1440-minute clock: identical times give 0; an earlier end crosses midnight. There are no dates, so two clock times cannot identify several elapsed days. Add and subtract modes accept a duration beyond one day but display the resulting 24-hour clock time. All parts must be whole numbers within their field bounds: time 0–23/0–59, duration 0–999 hours and 0–59 minutes. Invalid entries are rejected rather than silently clamped. Seconds, time zones and daylight-saving changes are not included.
Example
From 22:15 to 06:45 is 8 hours 30 minutes.
Fields and units
- What to calculate — list option
- Start hour — h. Whole numbers within the displayed range; invalid entries are not clamped to a boundary.
- Start minute — min. Whole numbers within the displayed range; invalid entries are not clamped to a boundary.
- End hour — h. Whole numbers within the displayed range; invalid entries are not clamped to a boundary.
- End minute — min. Whole numbers within the displayed range; invalid entries are not clamped to a boundary.
- Duration hours — h. Whole numbers within the displayed range; invalid entries are not clamped to a boundary.
- Duration minutes — min. Whole numbers within the displayed range; invalid entries are not clamped to a boundary.
How to use
- — Choose what to calculate.
- — Enter the times in hours and minutes.
- — Read the duration or the resulting time.
Method and limitations
- Calculation method
- Formula and logic
- Limitation
- There are no dates, so two clock times cannot identify several elapsed days. Seconds, time zones and daylight-saving changes are not included.
FAQ
What if the end time is earlier than the start?
It is treated as crossing midnight, which is what an overnight shift needs. The result is flagged on its own line.
Can the duration be longer than a day?
Durations you add or subtract can exceed 24 hours; the resulting time wraps around the clock.
Are seconds supported?
No. The calculator works in whole minutes, which is what shift and schedule arithmetic needs.
What happens to out-of-range values?
Out-of-range or fractional clock parts are rejected. Hours are not replaced with a boundary and minutes are not truncated; correct the entry before calculating.