Time Calculator
Time Calculator
Choose a calculation type below. Results update automatically as you change the times.
Full Breakdown
Time Calculator UK
Our Time Calculator combines two tools in one: an add/subtract calculator that finds a new clock time after adding or removing hours, minutes and seconds, and a duration calculator that works out exactly how much time falls between two clock times — including shifts that run past midnight.
How to Use the Time Calculator
- Choose a calculation type using the buttons at the top: “Add/Subtract Time” or “Duration Between Two Times”.
- For add/subtract: enter a start time, then the hours, minutes and seconds to add or subtract, and choose a direction. Quick presets are available for common amounts.
- For duration: enter a start time and an end time. If the end time is earlier than the start time, the calculator automatically assumes it falls on the next day — or you can force this manually with the overnight toggle.
- Results update automatically as you change the times, or click Calculate to refresh manually.
- Use Copy Results to copy a plain-text summary, or Print for a printable version.
How Overnight and Midnight-Spanning Times Are Handled
Working out a duration is straightforward when the end time is later in the same day, but many real situations — night shifts, overnight flights, sleep tracking — span midnight. If you enter an end time that’s earlier than the start time, this calculator assumes the end time falls on the following day rather than showing a negative duration. You can also tick “End time is next day” to force this manually, which is useful for a full 24-hour-plus shift where the start and end time happen to be the same clock time.
| Start Time | End Time | Result |
|---|---|---|
| 09:00 | 17:30 | 8h 30m (same day) |
| 22:00 | 06:00 | 8h 0m (assumed next day) |
| 23:45 | 00:15 | 0h 30m (assumed next day) |
Decimal Hours for Timesheets
Payroll and timesheet systems often need a duration expressed as a single decimal number rather than hours and minutes separately. This calculator converts every duration into decimal hours automatically — for example, 7 hours 30 minutes is shown as 7.50 decimal hours, and 45 minutes is shown as 0.75 decimal hours.
Common Uses for a Time Calculator
- Work shifts and timesheets: Find the exact length of a shift, including overnight shifts, and convert it to decimal hours for payroll.
- Meeting and appointment scheduling: Add a duration to a start time to find the finish time, or check how much time you have between two appointments.
- Cooking and recipes: Add preparation and cooking time to a start time to know when a dish will be ready.
- Travel and flights: Work out arrival times after a flight duration, or the total time elapsed for an overnight journey.
Important Assumptions
- The calculator works with times of day rather than specific calendar dates. If an end time is earlier than the start time, it assumes the end time is on the following day.
- If an end time is earlier than the start time, the calculator assumes the end time is on the following day rather than returning a negative duration.
- Decimal hours are rounded to 2 decimal places for display.
- The add/subtract calculator can wrap across more than one day if the amount added is large enough (for example, adding 30 hours), and this is shown as a day change in the results.
Frequently Asked Questions
How do I add or subtract time from a clock time?
Enter a start time, then the number of hours, minutes and seconds to add or subtract, and choose a direction. The calculator gives you the resulting time, and flags if the result falls on a different day.
How is the duration between two times calculated?
The calculator subtracts the start time from the end time to find the total elapsed time in hours, minutes and seconds. If the end time is earlier than the start time, it automatically assumes the end time falls on the next day.
What does decimal hours mean?
Decimal hours express a duration as a single number rather than hours and minutes separately, for example 7 hours 30 minutes becomes 7.50 decimal hours. This is commonly used for timesheets and payroll.
How does the calculator handle times that span midnight?
If the end time is earlier than the start time, the calculator automatically treats the end time as falling on the following day. You can also force this manually using the “End time is next day” toggle, which is useful for night shifts.
Can I calculate time with seconds, not just hours and minutes?
Yes. All time fields accept hours, minutes and seconds, so you can work with precise durations down to the second if needed.