Time & Date · Durations
Duration Converter
Convert any length of time between milliseconds, seconds, minutes, hours, days, weeks, months and years, or from and to HH:MM:SS — with a days-hours-minutes-seconds breakdown.
Your inputs
Quick start — try a typical case
Your result Live
HH:MM:SS
01:01:01
1h 1m 1s
- Milliseconds
- 3,661,000
- Seconds
- 3,661
- Minutes
- 61.01666667
- Hours
- 1.016944444
- Days
- 0.04237268519
- Weeks
- 0.006053240741
- Months (average)
- 0.00139214966
- Years (average)
- 0.0001160124717
How this is calculated
Seconds = Value × seconds per unit; HH = ⌊seconds ÷ 3600⌋, MM = ⌊(seconds mod 3600) ÷ 60⌋, SS = seconds mod 60
- Month / year
- Average Gregorian lengths: 30.436875 and 365.2425 days
- HH
- Total hours, not limited to 24
Durations convert by fixed factors — 60 seconds a minute, 3,600 an hour, 86,400 a day. Months and years are different: they vary in length, so they're converted using the long-run average of the Gregorian calendar and marked as averages. To count exact months between two dates, use the Date Difference Calculator instead.
Assumptions & sources
- A day is 86,400 seconds (no leap seconds); months and years are calendar averages.
- Results are shown to 10 significant figures; HH:MM:SS shows milliseconds when present.
- 1The International System of Units (SI Brochure) — the second — BIPM
- 2ISO 8601 — Date and time format (week numbering, calendar dates) — International Organization for Standardization
- 3Calendrical Calculations (Reingold & Dershowitz) — Cambridge University Press
Calculator ID TIME-DURATION-001 · version 2.0.0
Common questions
How many seconds are in a day?
86,400 (24 × 60 × 60). A week has 604,800 seconds.
How do I convert HH:MM:SS to seconds?
Hours × 3,600 + minutes × 60 + seconds. Switch the input to HH:MM:SS and the converter does it — 1:01:01 is 3,661 seconds.
Why are months and years marked 'average'?
Because a month can be 28 to 31 days and a year 365 or 366. The converter uses the Gregorian average (a year of 365.2425 days).