Time Calculator
Add or subtract two durations given in hours, minutes and seconds.
- First Duration2h 30m 0s
- Second Duration1h 45m 0s
The two durations side by side before they're added — the result (4h 15m 0s) is their sum.
ƒShow your work
- 1First duration: 2h 30m 0s = 9000 total seconds
- 2Second duration: 1h 45m 0s = 6300 total seconds
- 39000s + 6300s = 15300s
- 4Converted back: 4h 15m 0s
About the Time Calculator
This tool adds or subtracts two spans of time given in hours, minutes and seconds — the kind of arithmetic that gets surprisingly fiddly by hand once minutes roll past 60 or a subtraction goes negative. Type in two durations, pick plus or minus, and it carries the borrowing and carrying for you.
It gets used for anything measured in stretches of time rather than clock times: totaling up two recorded video clips before you trim them together, figuring out how much longer a recipe needs after part of it has already cooked, working out the gap between two lap times, or tallying hours across a couple of work sessions.
Everything runs in your browser — there's nothing to sign in for and nothing saved, so it's just as quick for a one-off kitchen timer question as it is for something you'd use daily.
How it’s calculated
Both durations are first converted to a single number of seconds (hours × 3600 + minutes × 60 + seconds), which sidesteps the awkward base-60 carrying that trips up manual addition. The two totals are then added or subtracted as plain numbers.
The result is converted back into hours, minutes and seconds for display. If a subtraction produces a negative total, the calculator flags it and shows the magnitude of the difference with a minus sign rather than wrapping around a clock.
Frequently asked questions
How do I add two times that total more than 24 hours?
Just enter them — this calculator works with durations, not clock times, so there's no 24-hour wraparound. Adding 20 hours and 10 hours correctly returns 30 hours rather than looping back to 6.
What does a negative result mean when subtracting?
It means the second duration was longer than the first, so the difference is shown as a negative value — for example subtracting 3h from 1h30m gives −1h 30m.
Can I use this for adding up work hours across a week?
You can add two durations at a time, so it works for combining a couple of shifts. For a full week of daily hours with overtime pay calculated automatically, the Time Card Calculator is the better fit.
Does this account for time zones or daylight saving?
No — this treats both entries as plain durations (like a stopwatch reading), not clock times tied to a specific zone or date, so there's nothing to adjust for.
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