Time Calculator
Add or subtract two time durations in HH:MM:SS and see the result instantly.
Example
Adding 1:30:00 and 0:45:30: 1:30:00 = 5400 s and 0:45:30 = 2730 s. Total = 8130 s = 02:15:30 (2.2583 hours).
How it works
Each duration is converted to total seconds (h*3600 + m*60 + s), the two totals are added or subtracted, then the result is converted back to HH:MM:SS. Negative results are shown with a leading minus sign.
Good to know
This Time Calculator takes two durations entered as hours, minutes and seconds, then adds or subtracts them to give you a clean HH:MM:SS answer. It's built for anyone who works with stretches of time rather than clock times of day — editors trimming video, runners stacking lap splits, billers totting up logged sessions, or musicians and podcasters checking total runtime. Pick the Add or Subtract toggle, fill in Duration A and Duration B, and the result updates the moment you type.
Reach for it whenever mental math gets awkward because seconds roll over into minutes and minutes into hours. Adding 1:30:00 to 0:45:30 isn't hard on paper, but doing it across several durations, or subtracting one timestamp gap from another, is exactly where people slip a carry. Because every value is first converted to raw seconds before being combined, you can also type loose numbers like 90 minutes or 200 seconds and let the tool normalize them for you.
The output gives you four readings at once: the formatted HH:MM:SS figure plus the same span expressed as total hours, total minutes and total seconds. Use the HH:MM:SS line for a human-readable answer and the total-seconds figure when you need to paste a value into a spreadsheet or another calculation. The decimal hours reading (for example 2.2583) is handy for timesheets or anything billed by the hour.
One thing to watch in Subtract mode: if Duration B is larger than Duration A, the result goes negative and is shown with a leading minus, such as -00:15:00, along with negative totals. That's a feature for measuring overshoot, not an error — just swap the two durations if you only want the size of the gap as a positive number.
Frequently asked questions
What happens if the subtraction gives a negative time?
The result is shown with a leading minus sign, for example -00:15:00, so you can see how much Duration B exceeds Duration A. Total hours, minutes and seconds also display as negative values.
Can I enter minutes or seconds greater than 59?
Yes. The calculator simply converts everything to total seconds first, so entering 90 minutes is treated as 1 hour 30 minutes and is normalized correctly in the HH:MM:SS result.
Is my data uploaded anywhere?
No — this calculator runs entirely in your browser. Your inputs never leave your device, and it works offline once loaded.
Is this calculator free?
Yes, completely free with no sign-up and no limits.
People also ask
How do I add two times together in hours and minutes?
Enter the first span as Duration A and the second as Duration B, keep the toggle on Add, and the calculator converts both to seconds, sums them, and shows the combined HH:MM:SS result instantly. For example, 1:30:00 plus 0:45:30 gives 02:15:30.
How do I convert HH:MM:SS into decimal hours?
Type the duration into one of the inputs and read the Total hours figure, which expresses the same span as a decimal — 02:15:30 shows as roughly 2.2583 hours. This is the format most timesheets and hourly billing systems expect.
Can this calculator handle durations longer than 24 hours?
Yes. It treats every value as an elapsed duration rather than a time of day, so a result like 30 or 50 hours is displayed normally without wrapping around at 24.
What is the difference between a time calculator and a time duration between two clock times?
This tool adds or subtracts two lengths of time (durations) such as 1:30:00 and 0:45:30. Finding the gap between two clock times, like 9:15 AM and 5:40 PM, is a different operation that subtracts one timestamp from another.
How do I subtract one duration from another?
Switch the toggle to Subtract, put the larger span in Duration A and the amount to remove in Duration B, and the result shows the remaining time. If B is bigger than A the answer turns negative with a leading minus.
Does the time calculator work without an internet connection?
Yes. All the math runs in your browser with JavaScript, so once the page has loaded it keeps working offline and none of your inputs are sent anywhere.
Why does my result show a minus sign?
A leading minus appears in Subtract mode when Duration B is larger than Duration A, indicating by how much B exceeds A. To get a positive answer, simply swap the two durations.
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