Time Calculator

Calculate the duration between two clock times, adjust a clock time, or add and subtract multiple durations. Total durations can exceed 24 hours.

The calculator works in whole seconds and keeps the day offset separate from the displayed 24-hour clock time, so a result that crosses midnight is never hidden.

Calculate a time duration

Enter two 24-hour clock times to get the elapsed hours, minutes, and seconds. When an end time is earlier than the start, the overnight option treats it as a time on the following day.

Add or subtract time

Add or subtract any non-negative number of hours, minutes, and seconds. The displayed clock result wraps to a 24-hour day while a separate day offset preserves the complete answer.

Add multiple durations

Add a row for each duration and choose + or −. For example, 1:30 + 2:45 + 0:50 = 5:05:00. Totals can exceed 24 hours or be negative. Blank rows are ignored.

How to calculate time online

1. For elapsed time, choose Time duration and enter the start and end clock times.
2. Keep the next-day option selected when an earlier end time means the range continues past midnight.
3. To adjust a clock time, choose Add or subtract, select the operation, and enter whole hours, minutes, and seconds.
4. Read the full duration or result time together with Decimal hours and Day rollover, then copy the result if needed.
5. To total several durations, choose Add multiple durations, add or remove rows, and select + or − for each. Read the total and calculation below.

Time Calculator FAQ

How do I calculate a time range that crosses midnight?

Leave Treat an earlier end time as the next day selected when the range crosses midnight. Clear it only when you intentionally want the same-day subtraction shown as a negative duration.

What is the difference between Time duration and Add or subtract?

Time duration finds the difference between two clock times. Add or subtract adjusts one clock time. Add multiple durations totals a list of durations without a start time.

What happens when I add or subtract more than 24 hours?

The clock result wraps within 24 hours, while Day rollover reports how many days forward or backward the full calculation moved. This keeps additions such as 30 hours from looking like a simple 6-hour result.

Does the calculator account for dates, time zones, daylight saving, or breaks?

No. The tool calculates clock times and durations; it does not apply calendar dates, time zones, daylight saving changes, work schedules, or automatic break deductions.

How do I add several durations without a start time?

Choose Add multiple durations. Enter each duration as hours:minutes or hours:minutes:seconds and choose + or − for each row. The result is a total duration, not a clock time: 23:00 + 2:00 gives 25:00:00, not 01:00:00.

Related tools: Time Unit Converter · Stopwatch · Countdown Timer · Online Clock · Date Calculator