Add and Subtract Time Without the Headache
Time is awkward to add by hand because it doesn’t use base 10: 60 minutes make an hour, 24 hours make a day, and months vary in length. Adding 7 hours 50 minutes to 5 hours 25 minutes in your head is surprisingly easy to get wrong. This calculator lets you add or subtract two durations made up of years, months, days, hours and minutes, and it carries over every unit correctly.
How to Use the Time Calculator
- Fill in Time 1 — the starting duration. Leave any unit you don’t need at zero.
- Click + to add or − to subtract.
- Fill in Time 2.
- The Final Result appears in normalised form (for example, 90 minutes is shown as 1 hour 30 minutes). Use Clear All to start again.
How the Carry-Over Works
| Unit | Equals |
|---|---|
| 1 hour | 60 minutes |
| 1 day | 24 hours = 1,440 minutes |
| 1 week | 7 days = 168 hours |
| 1 month (in this tool) | 30 days |
| 1 year | 12 months |
Using a fixed 30-day month keeps calculations predictable. If you need to work with actual calendar dates, where February has 28 or 29 days, use our Days Calculator.
Worked Examples
Adding durations
2 days 14 hours 45 minutes + 1 day 12 hours 30 minutes
- Minutes: 45 + 30 = 75 → 1 hour 15 minutes (carry 1 hour)
- Hours: 14 + 12 + 1 = 27 → 1 day 3 hours (carry 1 day)
- Days: 2 + 1 + 1 = 4
Result: 4 days, 3 hours, 15 minutes.
Subtracting durations
8 hours 10 minutes − 3 hours 45 minutes. You can’t take 45 from 10, so borrow 1 hour (60 minutes): 70 − 45 = 25 minutes, and 7 − 3 = 4 hours. Result: 4 hours, 25 minutes.
Weekly work hours
If you work 8 hours 45 minutes a day for 5 days, the total is 43 hours 45 minutes. In decimal hours (for timesheets and payroll) that is 43.75 hours.
Converting Minutes to Decimal Hours
Many timesheets and invoicing tools ask for hours as a decimal. Divide the minutes by 60:
| Minutes | Decimal hours |
|---|---|
| 15 min | 0.25 |
| 20 min | 0.33 |
| 30 min | 0.50 |
| 45 min | 0.75 |
A common mistake is writing 1 hour 30 minutes as “1.30 hours”. It is actually 1.5 hours; 1.30 hours is only 1 hour 18 minutes.
Who Uses a Time Calculator?
- Freelancers and employees totalling billable hours or overtime.
- Project managers adding up task estimates.
- Students planning study schedules or solving time-and-work problems.
- Video editors and podcasters adding clip lengths.
- Travellers adding flight and layover times.
Related Tools
- Days Calculator — days between two calendar dates.
- Age Calculator — exact age on any date.
- Unix Timestamp Converter — convert between dates and epoch time.