Free Online Time Duration Calculator
Calculate the exact duration between two clock times.
Leave both dates empty to measure a time of day. If the end time is earlier than the start time, it is treated as the next day. Fill both dates to anchor the interval to real calendar days.
About the Time Duration Calculator
A duration is the amount of time between two instants. Calculating it by hand is error-prone because hours and minutes use base sixty rather than base ten. If a shift starts at 22:45 and ends at 06:15 the next morning, a simple subtraction gives a negative number unless you remember to add a full day. This calculator handles the arithmetic for you, reports the interval in several useful formats, and makes overnight periods explicit rather than silently wrapping around midnight.
Time-only mode
Leave the two date fields empty when you only care about the clock difference. Enter a start time and an end time, then the tool subtracts the start from the end. If the end is later than the start, the result is the same-day interval. If the end is earlier, the calculator assumes the end belongs to the following day and adds twenty-four hours. That convention matches overnight shifts, flights, and maintenance windows. A start and end time that are identical are treated as a full twenty-four hour period.
Date-anchored mode
Fill in both dates when you need an interval that spans a known calendar period, such as 23:00 on Friday to 07:00 on Monday. The calculator combines each date with its time and subtracts the two instants, so weekends and multi-day gaps are included naturally. If the end is earlier than the start while both dates are provided, the tool reports an error instead of guessing, because an explicit date range should not silently wrap. The summary line repeats the interpreted start and end so you can confirm the result.
Reading the four outputs
The readable duration shows whole hours and minutes, plus seconds when they are present. Decimal hours divide total minutes by sixty and are the format most payroll and billing systems expect: 7 hours 30 minutes becomes 7.5. Total minutes is useful for scheduling blocks and rounding rules, while total seconds gives the exact interval for technical or scientific work. All four values describe the same span, so choose the one that fits the system you are entering it into.
Frequently asked questions
What happens if the end time is earlier than the start time?
Without dates, the end is treated as the next day. With both dates filled, the tool shows an error because the explicit range ends before it begins.
Why is 1 hour 30 minutes shown as 1.5 decimal hours?
Thirty minutes is half of sixty, so the decimal fraction is 0.5. Decimal hours divide the total minutes by sixty.
Does the result include breaks?
No. This tool measures the raw interval. Subtract unpaid breaks separately or use the work hours calculator for a shift with a break.