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Time Duration Calculator

A free online time duration calculator that finds the exact hours, minutes, and seconds between two times of day, or adds/subtracts a duration from a starting time - including automatic handling of times that span midnight.

How the duration between two times is calculated

The calculator subtracts the start time from the end time. If the end time is earlier in the clock than the start time, it assumes the end time falls on the next day and adds 24 hours automatically, rather than returning a negative result.

How add/subtract mode works

Add/subtract mode takes a starting time and a duration in hours, minutes, and seconds, then adds or subtracts that duration to find the resulting time - automatically noting if the result lands on a different day.

Why there's no date field

This calculator works purely in clock time (hours, minutes, seconds), not calendar dates - for finding the number of days, weeks, or months between two calendar dates, use the Date Difference Calculator instead.

Common Mistakes to Avoid

Forgetting a shift can cross midnight

Solution:

A shift from 10:00 PM to 6:00 AM is 8 hours, not a negative number - the calculator automatically assumes the end time is on the next day when it's earlier than the start time.

Confusing total minutes with hours and minutes format

Solution:

150 total minutes is the same as 2 hours 30 minutes - use whichever format matches what you need, both are shown in the result.

Mixing up add and subtract direction

Solution:

Double-check the Direction dropdown in add/subtract mode - subtracting a duration when you meant to add it (or vice versa) will land on the wrong time.

Expecting calendar date handling

Solution:

This tool only works with times of day, not calendar dates - a duration or result that crosses midnight is noted, but no specific calendar date is tracked.

Rounding seconds away for precise timing needs

Solution:

If exact timing matters (e.g. lap times, billing increments), make sure seconds are entered - by default fields may be left at 0 if not filled in.

Not double-checking AM/PM equivalent when reading native time inputs

Solution:

The time fields use your browser's native time picker, which may display in 12-hour or 24-hour format depending on your system settings - the calculated result is shown in 12-hour format with AM/PM for clarity.

Frequently Asked Questions

Choose 'Duration between two times', enter a start and end time, and press Calculate - the result shows hours, minutes, and seconds between them.
The calculator assumes the end time is on the next day and adds 24 hours before calculating the duration, rather than returning a negative number.
Yes - switch to 'Add or subtract a duration', enter a starting time, choose Add or Subtract, and enter the hours, minutes, and seconds to apply.
No - it works with time-of-day values only. For counting days, weeks, or months between two calendar dates, use the Date Difference Calculator instead.
Yes - both modes support seconds for precise timing.
In add/subtract mode, the calculator notes how many days forward or backward the result lands compared to the starting time.
No - every calculation runs locally in your browser. Nothing you enter is uploaded, logged, or stored on any server.

Free Online Time Duration Calculator

Find out exactly how much time is between two clock times, or add or subtract hours, minutes, and seconds from a starting time. Handles times that cross midnight automatically.

What You Get

  • The exact duration between two times, in hours, minutes, and seconds
  • Total minutes and total seconds for the same duration
  • An add/subtract mode for finding a resulting time from a duration
  • Automatic handling of durations and results that cross midnight

Who Uses This Calculator

Anyone tracking work hours, calculating shift lengths, timing a task, or figuring out what time something will end or started.