# Time Calculator – Add and Subtract Durations

URL: https://speedycalculator.com/calculators/everyday-life/time-calculator/
Last updated: 2026-10-25

> The time calculator adds or subtracts two durations given in days, hours, minutes and seconds, and shows the result broken into days, hours, minutes and seconds and as a total in hours, minutes or seconds.

## Inputs

- Duration 1 – days
- Duration 1 – hours
- Duration 1 – minutes
- Duration 1 – seconds
- Operation
- Duration 2 – days
- Duration 2 – hours
- Duration 2 – minutes
- Duration 2 – seconds

## Results

- Total seconds
- Days
- Hours
- Minutes
- Seconds
- Total hours
- Total minutes

## Formula

```
Total seconds = (d₁ × 86,400 + h₁ × 3,600 + m₁ × 60 + s₁) ± (d₂ × 86,400 + h₂ × 3,600 + m₂ × 60 + s₂)
Then split back into days, hours, minutes and seconds
```

## Explanation

Durations use a mixed base – 60 seconds, 60 minutes, 24 hours – so adding them by hand needs carrying at each step. Converting both to seconds, adding, then splitting back avoids errors.

### How to use the Time Calculator – Add and Subtract Durations

- **Duration 1 – days**
- **Duration 1 – hours**
- **Duration 1 – minutes**
- **Duration 1 – seconds**
- **Operation**
- **Duration 2 – days**
- **Duration 2 – hours**
- **Duration 2 – minutes**
- **Duration 2 – seconds**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter the two durations and choose add or subtract.

### Tips

- Check whether the end date should be included – event durations usually include it, elapsed time does not.
- Months have 28–31 days, so "one month" is counted by calendar date, not as 30 days.
- Use 24-hour time or set AM/PM carefully when entering clock times.
- Time zones and daylight-saving changes are not applied unless the calculator says so.

### Common mistakes to avoid

- Counting a 30-day month when a calendar month is meant (or the reverse).
- Forgetting leap years when counting days across February.
- Mixing decimal hours (7.5 h) with clock time (7:30).

### Inputs explained

FieldWhat to enterDuration 1 – daysA numberDuration 1 – hoursA numberDuration 1 – minutesA numberDuration 1 – secondsA numberOperationChoose one: Add (+), Subtract (−)Duration 2 – daysA numberDuration 2 – hoursA numberDuration 2 – minutesA numberDuration 2 – secondsA number

### What each result means

- **Total seconds** = ([Duration 1 – days]×86400 + [Duration 1 – hours]×3600 + [Duration 1 – minutes]×60 + [Duration 1 – seconds]) + [Operation]×([Duration 2 – days]×86400 + [Duration 2 – hours]×3600 + [Duration 2 – minutes]×60 + [Duration 2 – seconds])
- **Days** = sign([Total seconds])×floor([Absolute seconds]÷86400)
- **Hours** = sign([Total seconds])×floor(mod([Absolute seconds], 86400)÷3600)
- **Minutes** = sign([Total seconds])×floor(mod([Absolute seconds], 3600)÷60)
- **Seconds** = sign([Total seconds])×mod([Absolute seconds], 60)
- **Total hours** = [Total seconds]÷3600
- **Total minutes** = [Total seconds]÷60

### Example values

How the main result changes when **Duration 1 – days** changes and everything else stays at the example values above:

Duration 1 – daysDays0.510.751121.2521.5223

## Worked example

Inputs — Duration 1 – days: 1; Duration 1 – hours: 14; Duration 1 – minutes: 35; Duration 1 – seconds: 50; Operation: Add (+); Duration 2 – days: 0; Duration 2 – hours: 10; Duration 2 – minutes: 40; Duration 2 – seconds: 25.

Results — Total seconds = 177,375; **Days = 2**; Hours = 1; Minutes = 16; Seconds = 15; Total hours = 49.271; Total minutes = 2,956.25.

## FAQ

**How do I add times together?**
Add seconds, minutes, hours and days separately, carrying 60 seconds to a minute, 60 minutes to an hour and 24 hours to a day.

**What is 1 d 14:35:50 + 10:40:25?**
2 days 1 h 16 min 15 s.

**How many seconds in a day?**
86,400.

**What formula does the Time Calculator – Add and Subtract Durations use?**
Total seconds = (d₁ × 86,400 + h₁ × 3,600 + m₁ × 60 + s₁) ± (d₂ × 86,400 + h₂ × 3,600 + m₂ × 60 + s₂).