MasterTool

Time Calculator

Add or subtract time durations in hours, minutes and seconds — for shift totals, editing timelines, workout splits and elapsed-time math.

Loading calculator…

What this tool does

Add or subtract time durations in hours, minutes and seconds — for shift totals, editing timelines, workout splits and elapsed-time math. Durations are elapsed time, not clock times: hours may exceed 24 and minutes/seconds must be under 60. H:MM (without seconds) is also accepted. A subtraction that goes below zero returns a negative duration.

How to use the Time Calculator

  1. Enter or select operation.
  2. Enter or select first duration (h:mm:ss).
  3. Enter or select second duration (h:mm:ss).
  4. Read the calculated result; change any measurement to compare alternatives.

Formula

convert each H:MM:SS duration to total seconds (hours×3600 + minutes×60 + seconds), add or subtract, then split the result back into hours, minutes and seconds
operation
Operation
first
First duration (H:MM:SS)
second
Second duration (H:MM:SS)

Durations are elapsed time, not clock times: hours may exceed 24 and minutes/seconds must be under 60. H:MM (without seconds) is also accepted. A subtraction that goes below zero returns a negative duration.

Worked example

For time calculator, the following measurements illustrate the exact method: Operation: add; First duration (H:MM:SS): 02:30:00; Second duration (H:MM:SS): 01:15:30.

Inputs

  • OperationAdd (+)
  • First duration (H:MM:SS)02:30:00
  • Second duration (H:MM:SS)01:15:30

Result

  • Result duration (H:MM:SS)3:45:30
  • Result in decimal hours3.76
  • Result in total minutes225.5
  • Result in total seconds13,530

Results explained

Result duration (H:MM:SS)
Result duration (H:MM:SS) from the formula above. Durations are elapsed time, not clock times: hours may exceed 24 and minutes/seconds must be under 60. H:MM (without seconds) is also accepted. A subtraction that goes below zero returns a negative duration.
Result in decimal hours
Result in decimal hours from the formula above. Durations are elapsed time, not clock times: hours may exceed 24 and minutes/seconds must be under 60. H:MM (without seconds) is also accepted. A subtraction that goes below zero returns a negative duration.
Result in total minutes
Result in total minutes from the formula above. Durations are elapsed time, not clock times: hours may exceed 24 and minutes/seconds must be under 60. H:MM (without seconds) is also accepted. A subtraction that goes below zero returns a negative duration.
Result in total seconds
Result in total seconds from the formula above. Durations are elapsed time, not clock times: hours may exceed 24 and minutes/seconds must be under 60. H:MM (without seconds) is also accepted. A subtraction that goes below zero returns a negative duration.

Frequently asked questions

Enter both durations and choose Add. Each is converted to seconds first, so the minutes and seconds carry correctly — 2:30:00 + 1:15:30 = 3:45:30, never 3:45:60 or a decimal mix-up.

Yes. Choose Subtract to take the second duration from the first. If the second is larger, the result is shown as a negative duration (for example −0:15:00) and the totals are negative too.

Yes. These are elapsed durations, not times of day, so 30:00:00 is thirty hours. There is no wrap-around at midnight like there is with clock times.

No. H:MM is accepted and treated as zero seconds. Minutes and seconds must each be below 60; write 90 minutes as 1:30:00.

That tool finds the duration between two clock times on the same (or an overnight) day. This one does arithmetic on durations themselves — adding up several shifts, laps or task times, or subtracting one from another.