Hours Calculator
Find the duration between two clock times, add or subtract a duration from a time, or convert days, hours, minutes and seconds into decimal hours and total minutes.
Hours and duration formulas
Each time is converted to seconds after midnight:
Total seconds = hours × 3,600 + minutes × 60 + seconds.
For an interval, elapsed seconds equal end seconds minus start seconds. An overnight end receives an additional 86,400 seconds. Decimal hours equal total seconds divided by 3,600, and total minutes equal total seconds divided by 60.
For time addition or subtraction, the signed duration is added to the starting clock time. The result is split into a 24-hour clock value and a day offset.
Checked examples
| Calculation | Result | Decimal hours |
|---|---|---|
| 09:15 to 17:45 | 08:30:00 | 8.5 |
| 22:00 to 06:00 next day | 08:00:00 | 8 |
| 12:00 to 12:00 same day | 00:00:00 | 0 |
| 12:00 to 12:00 next day | 1 day, 00:00:00 | 24 |
| 23:30 + 2 hours | 01:30:00, day +1 | 2-hour duration |
| 1 day, 2 hours, 30 minutes | 1 day, 02:30:00 | 26.5 |
How to use the Hours Calculator
- Choose a clock-time interval, time addition/subtraction or duration conversion.
- Enter times using the 24-hour clock fields.
- For an overnight interval, select that the end is on the following day.
- Enter whole days, hours, minutes and seconds for a duration.
- Select Calculate hours and review the clock, duration and converted totals.
Limits and interpretation
- This calculator works with elapsed durations and clock times, not dates or time zones.
- It does not account for daylight-saving clock changes. Use actual dated timestamps when those changes matter.
- Hours in the duration fields are limited to 0–23; enter larger quantities as days plus hours.
- The “following day” option adds exactly 24 hours. It does not choose a calendar date.
- For payroll, unpaid breaks, overtime rules and estimated earnings, use the separate Time Card Calculator.
Frequently asked questions
How do I calculate hours overnight?
Enter the start and end clock times, then select “End time is on the following day.”
How do I convert 7 hours 45 minutes to decimal hours?
Choose “Convert a duration” and enter 7 hours and 45 minutes. The result is 7.75 hours.
Can the calculator subtract time?
Yes. Choose “Add or subtract a duration,” select subtraction and enter the duration components.
Does it calculate overtime or pay?
No. This tool performs general duration arithmetic. Time Card Calculator handles work periods, breaks, overtime thresholds and estimated pay.
Related calculators
Use the Time Card Calculator for shifts and payroll estimates, or the Date Calculator for calendar-day differences.