Scale & split
Multiply the exact result by a factor or divide it into equal millisecond-precise parts. Useful for pacing, production, editing, workouts and allocation.
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OneFreePlace · Tool #125
Add, subtract, scale and split time durations like real quantities.
Work with days, hours, minutes, seconds and milliseconds using natural duration notation, clock notation or ISO 8601. Audit each term, normalize the result, convert to decimal units, scale or divide it, build repeated-session totals and compare rounding without altering the exact answer.
✓ 1 ms precision✓ Flexible duration expressions
✓ ISO 8601 input/output✓ Scale + split
✓ Repeat + gap planner
Time Duration Calculator
Arithmetic · ISO 8601 · scale · split · repeat
Duration expression
Enter one duration—or calculate with several.
Examples: 2d 3h 15m · 01:30:00 · 1.5h + 20m · PT45M · 2h - 30m. In clock notation, 1:30 means 1h 30m. Bare numbers are rejected so the unit is never guessed.
Quick duration builderCreates a normalized positive duration term.
Expression auditEvery parsed term is shown before it contributes to the result.
Exact duration
1 ms precision—
normalized duration
Enter a valid duration expression.
Clock notation—total hours do not wrap at 24
ISO 8601—day/time subset: PnDTnHnMnS
Total hours—decimal hours
Total minutes—decimal minutes
Total seconds—decimal seconds
Total milliseconds—signed integer milliseconds
Normalized absolute parts—
—days
—hours
—minutes
—seconds
—milliseconds
Repeat + gap planner
Turn one duration into a full session: repeat it several times and optionally insert a gap between repetitions.
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Rounding comparison
The exact result remains untouched. These cards show what common rounding increments would do to the same duration.
Unit conversion snapshot
Signed conversions from the exact millisecond result.
Days—÷ 86,400,000 ms
Hours—÷ 3,600,000 ms
Minutes—÷ 60,000 ms
Seconds—÷ 1,000 ms
Supported input grammar
Units: d, h, m, s, ms, including decimals such as 1.5h or 2,25m. Clock: H:MM or H:MM:SS(.mmm). ISO: PnDTnHnMnS such as PT1H30M or P2DT45S. Join terms with + or −.
Each parsed value is rounded to the nearest millisecond. Months and years are intentionally excluded because they are calendar-dependent rather than fixed durations.
Why this is different from clock-time subtraction
A duration such as 30 hours is a quantity; it does not have a date, timezone or midnight by itself. That makes it safe to add, subtract, multiply and divide directly. For “09:00 to 17:30” or overnight clock spans, Tool #124 is the appropriate calculator.
i
Fixed-duration units only.One day here is exactly 24 hours, one hour is 60 minutes, and so on. Calendar months, years and daylight-saving transitions are not fixed-duration units, so they are deliberately not accepted in this calculator.