How to Calculate Time Duration
Learn how to calculate elapsed hours and minutes between two clock times.
Key idea
Learn how to calculate elapsed hours and minutes between two clock times.
Formula or method
Worked example
Start with the values in your question, substitute them into the formula, and keep the units consistent. For example, if a rate is given as 15%, use 0.15 when a formula requires a decimal.
Common mistakes
- Mixing percentage points with percentage change.
- Using different units for the same calculation.
- Rounding too early when several steps are involved.
Why the result can differ
Real-world calculations can include assumptions, rounding, fees, tax rules, calendar conventions, or other details. Treat simple calculator results as estimates when the underlying situation is more complex.
Intervals that cross midnight
A time interval from 22:30 to 01:00 cannot be interpreted correctly without knowing that the end occurs on the following day. The elapsed duration is 2 hours and 30 minutes under that assumption.
Clock time versus calendar time
Clock times describe positions within a day; dates establish which day those positions belong to. When schedules cross midnight or daylight-saving changes, include the date and relevant time-zone rules.
Practical planning
For ordinary same-day tasks, a duration calculator is usually sufficient. For multi-day schedules, combine date and time information explicitly.