About the Time Calculator
A time calculator converts between hours, minutes, and seconds, and totals a duration in each unit. It handles the sexagesimal arithmetic — base 60 — that makes time calculations more error-prone than decimal ones.
The formula
Total seconds = hours · 3600 + minutes · 60 + secondsThere are 60 seconds in a minute, 60 minutes in an hour, and 3,600 seconds in an hour. Converting everything to seconds first makes any subsequent arithmetic straightforward.
How to use this calculator
- 1Enter your Hours. The field starts at
2, which you can overwrite. - 2Enter your Minutes. The field starts at
30, which you can overwrite. - 3Enter your Seconds. The field starts at
0, which you can overwrite. - 4Read the result straight away — it recalculates as you type, so there is no button to press. Use Share to copy a link that reopens the page with your exact numbers filled in.
Worked example
| Input | Value |
|---|---|
| Hours | 2 |
| Minutes | 30 |
| Seconds | 0 |
Result
Total Time:
9,000 Seconds
150.00 Minutes
Those are the values the page loads with, so you can reproduce this result yourself and then change one field at a time to see what drives the outcome.
Understanding your result
The base-60 system comes from ancient Babylonian mathematics, chosen because 60 has many divisors — it divides evenly by 2, 3, 4, 5, 6, 10, 12, 15, 20, and 30. That made fractions convenient before decimals existed, and the convention has survived for both time and angular measurement.
The reliable method for any time arithmetic is to convert to a single unit, calculate, then convert back. Adding 2 hours 45 minutes to 3 hours 30 minutes by carrying in base 60 invites error; converting both to minutes, adding to 375, and converting back to 6 hours 15 minutes does not.
Things worth knowing
- Convert everything to one unit before calculating, then convert the result back.
- Payroll usually needs decimal hours: 90 minutes is 1.5 hours, not 1.30.
- 2.5 hours is 2 hours 30 minutes. Reading it as 2 hours 50 minutes is a common and costly error.
- A day is 86,400 seconds, except when a leap second is added — which has happened 27 times since 1972.
- Daylight saving transitions make one day 23 hours and another 25, which matters for shift calculations.
Frequently asked questions
How do I convert minutes to hours?+
Divide by 60. 150 minutes is 2.5 hours, which is 2 hours 30 minutes. The decimal and the hours-minutes forms are different notations for the same duration.
Why is time measured in base 60?+
It comes from Babylonian mathematics. Sixty has an unusually large number of divisors, which made fractions easy to express before decimal notation existed. The convention persists for time and angles.
How do I add times together?+
Convert both to seconds or minutes, add them, then convert back. Carrying in base 60 directly is where mistakes happen.
What is a decimal hour?+
An hour expressed with a decimal fraction rather than minutes. 1.75 hours is 1 hour 45 minutes. Payroll systems use decimal hours, which is why 1.45 hours is not 1 hour 45 minutes.