Everyday

Time Calculator

Add or subtract hours, minutes and seconds, and days if you need them. See the total in hours and minutes, in decimal hours, or as the time on the clock when it is done.

Enter two or more amounts of time to add or subtract them.

Exact calculation. Given your inputs, this is the answer — no estimation involved.

How this calculator works

Times are added by converting everything to seconds, adding or subtracting, and converting back. That carries every 60 minutes into an hour and every 24 hours into a day, which is where adding times by hand usually goes wrong: 45 minutes plus 30 minutes is 1 hour 15 minutes, not 75 minutes or 0.75 hours.

Enter up to ten amounts, choosing add or subtract for each one after the first. Decimals work too: 1.5 hours is 1 hour 30 minutes, and 0.1 hours is exactly 6 minutes.

The total is shown in words, as hours:minutes:seconds, and in decimal hours, minutes and seconds. Timesheets and payroll usually want decimal hours: 6 hours 15 minutes is 6.25 hours.

Add a start time to see what time it will be after the total — 9:30 PM plus 7 hours 45 minutes is 5:15 AM the next day — or subtract to count backward.

The formula

Exactly what happens to your numbers, step by step.

Everything in seconds

total = days × 86,400 + hours × 3,600 + minutes × 60 + seconds

Decimal hours

decimal hours = hours + minutes ÷ 60 + seconds ÷ 3,600

A worked example

Two stretches of work, 2 hours 45 minutes and 3 hours 30 minutes, starting at 8:30 AM.

What you enter

Start with: 2 hours 45 minutes
Add: 3 hours 30 minutes
Starting at: 8:30 AM

Step by step

Minutes: 45 + 30 = 75 minutes, which is 1 hour 15 minutes
Hours: 2 + 3 + 1 = 6 hours
Total: 6 hours 15 minutes
In decimal hours: 6 + 15 ÷ 60 = 6.25
From 8:30 AM: 2:45 PM

6 hours 15 minutes, or 6.25 hours, ending at 2:45 PM

Assumptions

Every result here rests on these. Change your inputs and the result changes with them.

A day is 24 hours, an hour 60 minutes and a minute 60 seconds.
Clock times follow a 24-hour day. On the two nights a year when the clocks change for daylight saving time, a wall clock will be an hour off from the result.
Each amount is entered as a positive number; the add or subtract switch decides its direction.

What this cannot tell you

For the time between two clock times, such as 9:00 AM to 5:30 PM, the hours between times calculator is quicker. For spans between dates, use the date difference calculator.

Questions people ask

How do I add hours and minutes?

Add the minutes, carry every 60 into an hour, then add the hours. For 1 hour 50 minutes plus 2 hours 25 minutes: 50 + 25 = 75 minutes, which is 1 hour 15 minutes, so the total is 4 hours 15 minutes.

How do I convert hours and minutes to decimal hours?

Divide the minutes by 60 and add them to the hours. 7 hours 45 minutes is 7 + 45 ÷ 60 = 7.75 hours, and 20 minutes is 0.33 hours to two places.

What time will it be in 8 hours?

Add 8 hours to the time now. If that passes midnight, take off 24 hours and it is the next day: from 7:00 PM, 8 hours later is 3:00 AM. Enter the hours and a start time above for any other case.

Can the total be negative?

Yes. Subtract more than you add — 1 hour minus 90 minutes — and the result is −30 minutes.

Sources and review

This calculator uses standard arithmetic with no external rules or published rates, so there is nothing to cite beyond the formulas shown above.

Methodology version 1.0.0 · Last reviewed October 1, 2026

Cite this calculator

For coursework, a resource list or your own site. How every calculator is built and checked is set out on the methodology page.

Citation

Chalk Calculator. (2026, October 1). Time Calculator (Methodology version 1.0.0). https://chalkcalculator.com/time-calculator/

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