Sumvia

Time Calculator

Add or subtract two durations expressed in days, hours, minutes, and seconds. The result is normalized (60 seconds carry to a minute, 60 minutes to an hour, 24 hours to a day) and shown with exact single-unit totals. For time between two clock times, use the Hours Calculator; for calendar dates, the Date Calculator.

Add or subtract durations

Example: 2 h 45 min + 1 h 30 min = 4 h 15 min.

Duration A
Duration B

Enter durations to see the result. Empty fields count as zero.

Working in base 60

Durations mix bases — 60 seconds to a minute, 60 minutes to an hour, 24 hours to a day — which is why adding them by hand goes wrong so easily. The calculator converts everything to seconds, does exact integer arithmetic, and converts back, so 2 h 45 min plus 1 h 30 min is 4 h 15 min (4.25 hours, 15,300 seconds) with the carry handled correctly.

Common uses

Summing tracked work sessions, combining video or audio segment lengths, adding cooking or lab steps, computing flight or travel legs with layovers, and checking how much of a time budget remains (subtract mode, where a negative result means you are over).

Frequently asked questions

Why does 2 h 45 min + 1 h 30 min give 4 h 15 min and not 3 h 75 min?

Time carries at 60, not 100: 75 minutes is 1 hour 15 minutes, so the extra hour carries up. The calculator normalizes automatically, the same way 10 + 5 carries in ordinary arithmetic.

Can a result be negative?

Yes — subtracting a longer duration from a shorter one gives a negative duration, shown with a minus sign. That is useful for "how far short of the target am I" questions.

What are the totals for?

The same duration expressed as a single unit: total hours for payroll, total minutes for scheduling, total seconds for scripting and media work. 4 h 15 min is 4.25 hours, 255 minutes, or 15,300 seconds.

Can I add clock times like 9:30 + 2:45?

Clock times and durations are different things — 9:30 am is a point, 2 h 45 min is a length. For time-of-day spans use the Hours Calculator; this page adds and subtracts lengths of time.

Values are processed locally in your browser and never transmitted. See the methodology page.