Time Calculator
Adjust the inputs below. Results update as you type.
How it works
Time arithmetic works in base 60 for minutes and seconds. To add times: add minutes, carry 60-minute groups to hours. Duration calculation crosses midnight if the end is earlier than start (add 24 hours to the end time). Convert decimal hours to H:MM by multiplying the decimal by 60. Time zones: UTC offsets range from UTC−12 to UTC+14. Daylight saving transitions add/remove one hour.
Input guidance
- Confirm date/time/unit settings before comparing outputs.
- If a task has optional fields, run both with and without them to understand impact.
- Save scenario variants when making practical decisions.
The formula
Add or subtract hours, minutes, and seconds by converting everything to a common unit (seconds), performing the arithmetic, then converting back.
Worked example
2h 45m plus 1h 30m = 4h 15m, found by adding 165 + 90 = 255 minutes = 4 hours 15 minutes.
More examples to test
- Quick-pass example: run default assumptions for a first estimate.
- Refined example: update one assumption at a time to isolate impact.
How to interpret results
Use outputs as operational estimates and pair them with local constraints, business rules, or provider requirements.
When this can be inaccurate
Utilities can miss local policy details, special-case rules, and environment-specific constraints.
Change history
- July 2026: Quality-reviewed for publication with formula checks and explanatory copy updates.
Site-wide corrections also appear on the corrections log.
Find productivity tools for everyday workflows
General recommendation, not professional advice.
Frequently asked questions
How do I add times that cross an hour?+
Convert to minutes or seconds, add, then convert back, carrying 60 minutes into an hour or 60 seconds into a minute.
How do I subtract a later time from an earlier one?+
If the result is negative, it crossed midnight; add 24 hours to get the elapsed time across the day boundary.
What about 12- vs 24-hour format?+
Both represent the same instant. 24-hour (military) time avoids AM/PM confusion, especially for durations that span noon or midnight.
Why are outputs slightly different from another tool?+
Different tools can use different rounding rules, default assumptions, and treatment of edge cases.
How can I improve estimate reliability?+
Use verified inputs from real records and re-run calculations after major assumption changes.