Duration arithmetic
Add shifts, media segments, tasks, or exercise intervals beyond a 24-hour clock.
Duration and clock-time calculator
Add, subtract, and compare time precisely.
Calculate duration arithmetic and overnight elapsed time without converting everything to decimals by hand.
Use the free toolRuns in this browser
time calculator
Choose duration mode for quantities of time or clock mode for start/end times. Negative results and day rollover are shown explicitly.
Result
The jobs this tool completes
Built around the failure points.
Overnight elapsed time
Calculate across midnight deliberately instead of receiving a negative surprise.
Multiple useful formats
See normalized HH:MM:SS, total seconds, decimal hours, and a step audit.
Workflow
From input to an auditable output.
- Choose duration arithmetic or elapsed clock time.
- Enter values in HH:MM:SS and set the operation or overnight behavior.
- Review the normalized result, day rollover, decimal total, and calculation steps.
Learn the details
Use the result with fewer surprises.
Guide
How to add hours, minutes, and seconds
Add time durations reliably by normalizing seconds and minutes, including totals longer than 24 hours.
Read guide →GuideHow to calculate elapsed time across midnight
Work out elapsed clock time when an end time falls on the following day without confusing dates and durations.
Read guide →Common questions
What this tool does—and does not do.
Duration arithmetic
Add shifts, media segments, tasks, or exercise intervals beyond a 24-hour clock.
Overnight elapsed time
Calculate across midnight deliberately instead of receiving a negative surprise.
Multiple useful formats
See normalized HH:MM:SS, total seconds, decimal hours, and a step audit.
Does this guarantee the result will be accepted elsewhere?
No. The tool completes and explains its calculation or transformation, but another platform can apply different limits, rules, encoders, or policies. Verify consequential output in the destination.
Ready
Calculate time
Return to the tool with your inputs still in this tab.