Add, Subtract & Combine Durations

This tool works with pure durations (no calendar dates required). It's useful for adding up video clip lengths, calculating total work time from a list of sessions, or figuring out what remains after subtracting elapsed time from a total.

Supported Formats

The parser accepts many common formats so you can paste durations from different sources without reformatting them first. Supported: 1:30:00, 1:30, 1h 30m, 1h30m, 90m, 5400s, 1.5h, or plain numbers (treated as seconds). Negative values are also accepted.

Operations

Add sums all durations. Subtract starts from the first duration and subtracts the rest. Multiply multiplies the total by a factor: useful for estimating repeated tasks. Divide splits the total: useful for calculating per-unit time. Average divides the total by the count of items.

Worked examples

Adding video clip durations: four clips of 1:32:10, 0:45:20, 2:10:05, and 0:55:30 - add them to get the total raw footage duration before editing.
Subtracting a lunch break: total shift 8:30:00 minus break 0:45:00 = 7:45:00 of billable time.
Estimating a repeated task: one task takes 0:08:30 - multiply by 24 to estimate the time for a batch job.

Edge cases

Durations greater than 24 hours: results display as 25:30:00 (not rolling over to the next day). Durations are elapsed time, not clock readings.
Negative results: subtracting more time than is available produces a negative duration, displayed with a minus prefix.

ISO 8601 duration format

The ISO 8601 standard defines a compact duration format used in APIs, databases, and programming languages:

P1DT2H30M    (1 day, 2 hours, 30 minutes)
PT45S        (45 seconds)
P0Y2M10DT0H0M30S  (2 months, 10 days, 30 seconds)

The P prefix stands for "period"; T separates date components (Y, M, D) from time components (H, M, S). Many calendar and scheduling APIs accept durations in this format. This tool's results can be transcribed to ISO 8601 format for use in code.