Time Calculator adds or subtracts hours, minutes and seconds from a base time, or totals a whole list of durations into one running sum. Switch between the two modes: in Add/Subtract, enter a base time plus a duration to add or take away, and the tool carries minutes into hours (and borrows back the other way) so a result like 95 minutes always normalizes to 1 hour 35 minutes. In Sum mode, add as many duration rows as you need — shift lengths, task times, workout splits — and get one combined H:MM:SS total, plus decimal hours for timesheets. Negative results, such as subtracting a longer duration from a shorter one, are shown clearly with a leading minus sign instead of wrapping around a 24-hour clock. Everything is calculated locally on your device as you type.
Features
Add or subtract hours, minutes and seconds from a base time in one step
Sum an unlimited list of durations into a single H:MM:SS total
Automatic carry and borrow — 95 minutes normalizes to 1h 35m without manual math
Negative results are shown with a clear leading minus sign, not a wrapped clock
Decimal-hours output alongside H:MM:SS, handy for timesheets and payroll
Total seconds and total minutes shown for quick reference
Add or remove duration rows on the fly when summing a list
Copy the resulting time or the full breakdown with one click
How to use the Time Calculator
Choose Add/Subtract two times, or Sum a list of durations
Enter hours, minutes and seconds for the base time and the duration
Pick Add or Subtract, or add more rows to sum
Read the resulting time, decimal hours and total seconds, then copy
Example
Input
2:30 + 1:45
Output
4:15:00
Common errors & troubleshooting
Adding 1h and 90m gives an unexpected hour count. — Time Calculator carries overflowing minutes into hours automatically, so 1:00:00 + 0:90:00 correctly becomes 2:30:00 — no need to pre-convert 90 minutes yourself.
Subtracting a longer duration produces a confusing result. — When the duration being subtracted is larger than the base time, the result is negative and shown with a leading minus sign (e.g. -0:30:00) instead of wrapping to the next day.
Summed durations don't match a manual add-up. — Double-check each row's seconds field — a blank field counts as 0, but a stray non-numeric character (like a colon) makes that row invalid and is flagged in red.
Decimal hours look off compared to H:MM:SS. — Decimal hours convert minutes and seconds to a fraction of an hour (e.g. 30 minutes = 0.5), which is expected for timesheet totals and differs from the H:MM:SS view.
Frequently asked questions
What can the Time Calculator add or subtract?
It works with hours, minutes and seconds for both a base time and a duration. Use Add to move a time forward or Subtract to move it back, with automatic carry and borrow across the h/m/s fields.
How does the Time Calculator handle a negative result?
If the duration you subtract is larger than the base time, the result is negative. Time Calculator shows this with a single leading minus sign, like -1:15:00, rather than wrapping around a 24-hour clock.
Can the Time Calculator sum more than two durations at once?
Yes. Switch to Sum a list of durations, add as many rows as you need, and the tool totals every h/m/s row into one combined H:MM:SS and decimal-hours result.
Does the Time Calculator show decimal hours for timesheets?
Yes. Alongside the H:MM:SS result, Time Calculator shows the same duration as decimal hours (e.g. 1:30:00 becomes 1.5), which is the format most timesheet and payroll tools expect.
Does the Time Calculator upload the times I enter?
No. Time Calculator runs entirely in your browser — the hours, minutes and seconds you enter never leave your device and are not sent to ArrayKit.
What happens if I leave an hours, minutes or seconds field blank?
A blank field is treated as 0, so you can enter just minutes (e.g. only 45 in the minutes box) without filling in hours and seconds.
Related tools
Time Card Calculator — Total daily and weekly work hours from clock-in/out times minus breaks.
Time Duration Calculator — Calculate the hours and minutes between two times of day, even across midnight.
Duration Converter — Convert a duration between seconds, minutes, hours, days, HH:MM:SS and human formats.
Date Calculator — Add or subtract years, months, weeks and days from a date to find the resulting date.