# Time Calculator

> Add or subtract two durations given in days, hours, minutes and seconds, and see the answer in each unit and as decimal hours.

Category: Date, time & lifestyle · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/time-calculator

Enter two lengths of time and add or subtract them. The answer is normalised, so 90 minutes becomes 1 hour 30 minutes, and is also given in decimal hours.

Also called: Duration calculator, Hours and minutes calculator.

## Inputs
- First: days (default 1; optional)
- First: hours (default 2; optional)
- First: minutes (default 30; optional)
- First: seconds (default 0; optional)
- Operation (options: Add (+), Subtract (−); default add)
- Second: days (default 0; optional)
- Second: hours (default 23; optional)
- Second: minutes (default 45; optional)
- Second: seconds (default 30; optional)

## Results
- Result
- In decimal hours
- In minutes
- In seconds

## Formula

```
Seconds = 86,400 × days + 3,600 × hours + 60 × minutes + seconds for each duration; add or subtract, then split back into days, hours, minutes and seconds.
```

Where:
- 86,400: seconds in a day
- 3,600: seconds in an hour

## Worked example
1. First: 86,400 + 7,200 + 1,800 = 95,400 s.
2. Second: 82,800 + 2,700 + 30 = 85,530 s.
3. Sum: 180,930 s = 2 days (172,800 s) + 2 h (7,200 s) + 15 min (900 s) + 30 s.

**Result:** 1 day 2 h 30 min plus 23 h 45 min 30 s is 2 days 2 h 15 min 30 s, or about 50.26 hours.

## What the result means

Decimal hours are what timesheets and invoices usually need: 15 minutes is 0.25 h, 30 minutes 0.5 h and 45 minutes 0.75 h. A negative result means the second duration is longer than the first.

## Assumptions and limits
- A day is exactly 24 hours (durations, not calendar days across a daylight-saving change).
- To find the time between two clock times, use the Hours Calculator.

## Questions

### How do I convert minutes to decimal hours?

Divide by 60. For example 45 minutes ÷ 60 = 0.75 hours, so 7 h 45 min is 7.75 hours.

### Can I enter 90 minutes?

Yes. Any field can exceed its usual range; the result is normalised to 1 h 30 min.

## Related calculators
- [Hours Calculator](https://calculators.geekmidst.com/calculators/hours-calculator)
- [Time Card Calculator](https://calculators.geekmidst.com/calculators/time-card-calculator)
- [Date Calculator](https://calculators.geekmidst.com/calculators/date-calculator)

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/time-calculator