MathIsimple
Time Duration Calculator

Time Duration Calculator

Find exactly how long it is between two times — same day, overnight, or spanning several dates — in hours and minutes, total minutes, and decimal hours.

100% FreeOvernight Ranges HandledMulti-Day Durations
Duration Between Two Clock Times
If the end time is earlier than the start time, the duration rolls past midnight automatically

How Time Duration Is Calculated

Duration is the difference between two points on the clock, and the reliable way to find it is to convert both times to minutes since midnight and subtract. Worked example — 8:45 AM to 5:15 PM: the start is 8×60 + 45 = 525 minutes; the end is 17×60 + 15 = 1,035 minutes; the difference is 510 minutes = 8 h 30 min. Subtracting the written times digit-by-digit (17:15 − 8:45) forces you to borrow 60 minutes, which is where most hand-calculation errors happen — the minutes-since-midnight method never needs borrowing.

Common Shift Durations Chart

Time rangeDurationDecimal hours
9:00 AM – 5:00 PM8 h 00 min8.00 h
8:30 AM – 4:15 PM7 h 45 min7.75 h
7:00 AM – 3:30 PM8 h 30 min8.50 h
11:00 PM – 7:00 AM (overnight)8 h 00 min8.00 h
10:15 PM – 6:45 AM (overnight)8 h 30 min8.50 h
12:00 PM – 12:00 AM12 h 00 min12.00 h

Overnight rows use the +24 h rule: when the end time is earlier than the start time, the range continues into the next day.

Durations That Span Multiple Days

For anything longer than 24 hours — a trip, an assignment deadline, a rental window — the clock times on both ends matter. Worked example: a car rented Friday 3:00 PM and returned Monday 10:00 AM is out for 2 days 19 hours, not “3 days”: Friday 3 PM → Sunday 3 PM is exactly 2 days, and Sunday 3 PM → Monday 10 AM adds 19 hours. Rental companies bill in 24-hour blocks from pickup time, so that return is charged as 3 days only because 2 days 19 h exceeds the 2-day mark — knowing the exact duration tells you whether returning 5 hours earlier saves a full day’s charge.

Duration vs. the Other Time Tools

This page answers one question: how long between two moments? If you need to add or subtract several durations (2 h 45 min + 1 h 30 min − a 45-minute break), use the time calculator. If you track a whole week of shifts with breaks and pay, the hours calculator is built for timesheets. And for whole-day counts between calendar dates (deadlines, ages, countdowns), the date calculator counts days, weeks, and business days without clock times.

Frequently Asked Questions

How do I calculate the duration between two times?
Convert both times to minutes since midnight, then subtract. From 8:45 AM to 5:15 PM: (17×60+15) − (8×60+45) = 1035 − 525 = 510 minutes = 8 h 30 min. If the result is negative, the range crosses midnight — add 24 hours (1,440 minutes).
How does the calculator handle overnight durations?
If the end time is earlier than the start time, the calculator adds 24 hours, following time-card convention. A 9:30 PM to 5:45 AM shift is 5:45 + 24:00 − 21:30 = 8 h 15 min.
What is the duration between two dates and times?
The calculator subtracts the full timestamps, so it accounts for the clock time on both days. From Mar 3, 9:00 AM to Mar 6, 5:00 PM is 3 days 8 hours — not 3 days — because the end clock time is 8 hours later than the start clock time.
How do I convert a duration to decimal hours?
Divide the minute part by 60 and add it to the hours: 8 h 30 min = 8 + 30/60 = 8.50 decimal hours. Payroll systems multiply decimal hours by the hourly rate, so 8 h 30 min at $20/hour pays 8.5 × 20 = $170.
What's the difference between elapsed time and duration?
They're the same quantity — the length of the interval between a start and an end point. "Elapsed time" is more common for something already finished (a race, a shift); "duration" is used for planned intervals (a flight, an exam). Both are measured the same way.
How many minutes are in a full day?
24 hours × 60 = 1,440 minutes, or 86,400 seconds. That constant is what the calculator adds when a time range wraps past midnight, and it's why parking garages and billing systems often price in fractions of 1,440.
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