Time Calculator
Add or subtract hours, minutes, and seconds. Calculate duration between two times. Convert time to decimal hours.
Add / Subtract Time
Time Between
About this calculator
The Time Calculator adds or subtracts hours, minutes and seconds, finds the duration between two clock times and converts a time to decimal hours. It is the tool for timesheets, shift lengths, recipes, video editing and any sum where 60 minutes make an hour.
Adding 1:45 and 2:30 is not 3:75. This calculator carries the minutes correctly into hours, so you get 4:15. The 'add row' option lets you add up a whole column of durations in one go.
How to use it
- For addition or subtraction, choose + or −, enter hours, minutes and seconds, and use + Add Row for more values, then press Calculate.
- For a gap between two clock times, enter the start time and end time and press Calculate Duration.
- Read the result in hours, minutes and seconds and as decimal hours.
How the arithmetic works
Everything is converted to seconds: Total seconds = H × 3,600 + M × 60 + S. The values are added or subtracted, then converted back: Hours = floor(Total ÷ 3,600), Minutes = floor((Total mod 3,600) ÷ 60). Decimal hours are Total seconds ÷ 3,600, so 2 hours 30 minutes is 2.5 hours.
Worked example
1 h 45 min + 2 h 30 min
| Sum | 4 h 15 min |
| Decimal hours | 4.25 |
| Difference (2 h 30 − 1 h 45) | 0 h 45 min |
For a shift from 09:15 to 17:50 the duration is 8 h 35 min, or 8.58 decimal hours.
Tips and common mistakes
- Convert to decimal hours for payroll. 8 h 35 min is 8.58 hours, not 8.35.
- Subtract unpaid breaks from the end-minus-start result.
- Times past midnight need the date. For overnight shifts, use the Date Duration Calculator.
- Use seconds for races, videos and lab work.
- Keep a column of durations and use Add Row to total them.
Frequently asked questions
How do I add hours and minutes?
Add the minutes first, carry every 60 minutes into the hours, then add the hours.
How do I convert minutes to decimal hours?
Divide the minutes by 60. Thirty minutes is 0.5 hours.
What is 8 hours 35 minutes in decimal?
8.58 hours.
How do I calculate the time between two times?
Subtract the start from the end. If the end is earlier, the span crosses midnight.
Can I subtract time?
Yes, switch the operator to minus.
Does it handle seconds?
Yes.