Time
Time Duration Calculator
Calculate the exact duration between two times, including across midnight.
Time Duration Calculator
8h 0m 0s
Two clock times, one straightforward-looking subtraction — except when the end time is earlier in the day than the start time, which almost always means the span crosses midnight rather than being a negative duration, and getting that distinction right is the whole job of this tool.
Meeting length calculations, video and audio editing timestamps, and simple day-to-day time-tracking are all common real uses for this tool, and in each case, the overnight-crossing edge case is the single most common source of an incorrect result if it isn't handled explicitly.
How the Time Duration Calculator works
Both times are converted to minutes since midnight and subtracted. If the result would be negative and the span is meant to cross into the next day, the tool adds a full 24 hours' worth of minutes before subtracting — correctly turning what would look like a negative number into the real overnight duration.
This tool's overnight-crossing logic is the same core routine the Work Hours Calculator builds on for shift calculations — the difference is that the Work Hours Calculator additionally subtracts break periods and totals multiple shifts, while this tool answers the single-duration question on its own.
Worked example
From 22:15 to 06:45 the next morning: a naive subtraction (06:45 minus 22:15) gives −930 minutes, which is wrong for an overnight span; adding 24 hours (1,440 minutes) gives 1,440 − 930 = 510 minutes, or 8 hours 30 minutes — the correct duration.
Edge cases this tool handles correctly
- Same-day vs. overnight ambiguity
- A start of 09:00 and end of 17:00 versus a start of 17:00 and end of 09:00 both "look" plausible as either an 8-hour same-day span or a 16-hour overnight span depending on direction — the tool requires you to specify which, rather than guessing.
- Daylight Saving Time transitions
- This tool works in pure clock time with no date or time zone attached, so it can't detect a Daylight Saving Time changeover — a duration spanning a "spring forward" night will read one hour longer than the clock actually experienced, and a "fall back" night one hour shorter, the same phenomenon explained in more depth on the site's DST blog post.
- Exact-hour durations
- A duration landing precisely on the hour still displays minutes and seconds correctly (as zero) rather than dropping to a bare hour figure.
- Durations shorter than a minute
- Very short spans (a handful of seconds or a few minutes) are computed with the same minutes-since-midnight subtraction as a multi-hour span — there's no separate rounding rule applied just because the duration happens to be brief.
- Durations longer than 24 hours
- This tool is built for a single day/overnight span; a duration meant to span multiple full days is better handled with the Days Between Dates tool for the day portion and this tool for any partial-day remainder.
- Twelve-hour vs. twenty-four-hour input formats
- Entering a 12-hour clock time requires an unambiguous AM/PM marker, since "7:00" alone is genuinely ambiguous between morning and evening — the tool also accepts 24-hour format directly, which sidesteps the AM/PM question entirely for users more comfortable with that format.
- Video and audio timestamp durations
- Editors trimming a clip between two timestamps are really asking this same question in disguise — a scene from 01:12:30 to 01:47:05 in a long recording is exactly a duration calculation between two clock-format times, just labeled as elapsed footage instead of elapsed hours in a day.
Frequently asked questions
Does it handle overnight shifts automatically?
Yes — when the end time is earlier than the start time and you indicate an overnight span, it adds 24 hours before subtracting instead of returning a negative number.
Can I enter times in 24-hour format instead of AM/PM?
Yes — 24-hour format is accepted directly and avoids any AM/PM ambiguity altogether.
Can it show the duration as a decimal figure instead of hours and minutes?
Yes — alongside the hours-and-minutes result, a decimal-hours figure (like 8.5 instead of 8h 30m) is available, useful for anyone feeding the result into a spreadsheet or billing calculation.
Does it adjust for Daylight Saving Time?
No — it works in pure clock time without a date or time zone attached, so a span crossing a DST changeover night will be off by an hour from the real elapsed time.
What units does the result show?
Hours and minutes by default, with a decimal-hours option useful for payroll.
How is this different from the Work Hours Calculator?
This tool does a single duration between two clock times; the Work Hours Calculator adds break deductions and totals multiple shifts for time-card purposes.
Does it handle very short durations accurately, like just a few minutes?
Yes — the same exact-minute subtraction method applies regardless of how short or long the duration is.
Can it show the result in total minutes instead of hours and minutes?
Yes — a total-minutes figure is available alongside the hours-and-minutes breakdown.