Tools To India

Time Calculator

Enter two durations to add or subtract them, and get the result in clock format and as decimal hours.

Last updated

First duration
Second duration
Operation

The result updates as you type. Nothing you enter is saved, sent to a server or shared.

Result

10:15:00

hours : minutes : seconds

The same result in other units

Decimal hoursUse this for timesheets and hourly billing.
10.25
Total minutes
615
Total seconds
36,900

How this calculator works

Adding durations trips people up because time is base-60 rather than base-10. Adding 45 minutes to 45 minutes gives 1 hour 30 minutes, not 90 of anything decimal.

The reliable method is to convert everything to a single unit, do the arithmetic there, and convert back. This calculator converts both durations to seconds, adds or subtracts, then splits the total back into hours, minutes and seconds.

Decimal hours are shown alongside because that is what timesheets, hourly billing and payroll systems usually want. 8 hours 45 minutes is 8.75 hours, not 8.45 — a conversion that costs people money surprisingly often.

Negative results are supported and clearly marked, which matters when subtracting a longer duration from a shorter one.

The formula

Converting to seconds and back

total seconds = (hours × 3600) + (minutes × 60) + seconds hours = total ÷ 3600, rounded down minutes = (total mod 3600) ÷ 60, rounded down seconds = total mod 60

Decimal hours

decimal hours = total seconds ÷ 3600

45 minutes is 0.75 hours, not 0.45. This is the single most common time-conversion error on timesheets.

Worked example: 8 hours 45 minutes plus 1 hour 30 minutes

Adding a normal working day to overtime.

Step-by-step calculation for the worked example
First duration in seconds31,500
Second duration in seconds5,400
Total seconds36,900
Hours (36,900 ÷ 3600)10
Remaining seconds900
Minutes (900 ÷ 60)15
Result10:15:00
Decimal hours10.25

The result is 10 hours 15 minutes, or 10.25 decimal hours. Billing 10.15 hours instead of 10.25 would understate the time by six minutes.

Things worth knowing

  • Decimal hours and clock time are different. 8 hours 45 minutes is 8.75 decimal hours. Entering 8.45 into a payroll system understates the time.
  • Minutes and seconds must each be below 60. If you have 90 minutes, enter it as 1 hour 30 minutes.
  • This adds and subtracts durations, not clock times across a date boundary. For that, use the date calculator.
  • For payroll, confirm whether your employer rounds time to the nearest five, ten or fifteen minutes before relying on an exact figure.

Frequently asked questions

How do I convert 45 minutes to decimal hours?
Divide by 60: 45 ÷ 60 = 0.75. So 8 hours 45 minutes is 8.75 hours. Writing 8.45 is a different and smaller number, and it is the most common mistake on manually filled timesheets.
Can I add more than 24 hours?
Yes. Durations are not clock times, so there is no wrap-around at 24. Entering 30 hours is perfectly valid and the result will show more than 24 hours where appropriate.
What does a negative result mean?
That the duration you subtracted was longer than the one you started with. The result is shown with a minus sign — useful when tracking a shortfall against a target, such as hours still owed in a month.

Sources

Every figure on this page is traceable to the official source below. If a source has changed since the date shown, please tell us and we will correct it.