Time Converter: Seconds, Minutes, Hours, Days and Years

The time converter changes a value between ten units: nanosecond (ns), microsecond (μs), millisecond (ms), second (s), minute (min), hour (h), day (d), week (wk), month (mo) and year (yr). Every one converts by a single fixed multiple of the second.

Updated 2026-09-30Reviewed by CalcX Editorial Team5 sources4 min read

How to use it

Pick the source unit on the left card and the target on the right; both dropdowns list the same ten units.
Type on either side and the other converts as you type; the middle button swaps the units.
The focused field takes expressions: 60+30 shows a quiet = 90 hint; Enter or = settles it.
An unfinished 3 + shows = ? and keeps the last settled value.
The All Units list repeats the duration in every unit; click a row to move it to the focused side.

Worked examples

Every readout below comes from this converter.

Input (left card)	Row shown	Readout
1 min	Second	60 s
1 d	Minute	1,440 min
1 wk	Hour	168 h
1 mo	Second	2,592,000 s
1 yr	Week	52.1428571429 wk
1 yr	Month (30 days)	12.1666666667 mo
12 mo	Year (365 days)	0.9863013699 yr

More readouts: a 90-minute programme is 1.5 h; 1 yr is 8,760 h and 31,536,000 s; twelve fixed months total 360 d; a million seconds is 11.5740740741 d.

The second and its fixed factors

The second is the base this converter stores, defined since 1967 by a fixed atomic frequency — caesium-133's hyperfine transition at 9,192,631,770 Hz — not by the Earth's rotation. The sub-second rows are decimal fractions of it: 1 ns = 10⁻⁹ s, 1 μs = 10⁻⁶ s, 1 ms = 10⁻³ s.

Every larger unit is a fixed multiple. NIST SP 811 lists the minute, hour, day and 365-day year as exact factors, so 1 min = 60 s, 1 h = 3,600 s, 1 d = 86,400 s and 1 yr = 31,536,000 s; the week and fixed month complete the set at 604,800 s and 2,592,000 s.

Reading results and limits

Results carry up to 12 significant digits. Between 10⁻¹⁰ and 10¹⁵ they print with comma grouping and up to 10 decimal places; outside that band, exponential form with six decimals. Stored values keep more digits than the screen.

Input (left card)	Row shown	Readout
1 wk	Nanosecond	604,800,000,000,000 ns
1 mo	Nanosecond	2.592000e+15 ns
0.0000000001 s	Second	0.0000000001 s
0.00000000001 s	Second	1.000000e-11 s
250 ms	Second	0.25 s
1 ms	Nanosecond	1,000,000 ns
-120 s	Minute	-2 min

The nanosecond rows sit either side of the 10¹⁵ boundary: a week prints in full, a month switches to 2.592000e+15. Likewise 10⁻¹⁰ s reads 0.0000000001 s and one power of ten lower 1.000000e-11 s; negatives convert normally.

The tool does not do calendar arithmetic: adding a month to a date, counting weekdays or shifting between time zones needs a calendar, not a fixed factor — the date calculator handles those. This page converts durations only.

The fixed month and year

The trap sits in the two calendar-looking rows. This month is 30 days and this year is 365 days, pinned so every conversion stays checkable by hand. Twelve months therefore equal 360 d and convert to 0.9863013699 yr, five days short; read the other way, 1 yr is 12.1666666667 mo.

Calendar lengths refuse to settle: a Gregorian month runs 28 to 31 days (mean 30.436875), a calendar year 365 or 366, and a UTC day can stretch to 86,401 s with a leap second — none has one conversion factor. The week alone still matches the calendar.

Where it fits

Schedules and work plans

A 90-minute programme is 1.5 h; a 40-hour week reads 1.6666666667 d, and 2,880 minutes is 48 h.

Timing and logs

The sub-second rows come into their own here: 250 ms is 0.25 s, 1 ms is 1,000,000 ns, and a week reads 604,800,000 ms. The speed converter divides by the same 3,600-second hour.

Longer sums

A million seconds is 11.5740740741 d — 277.777777778 h — past a week, short of a fortnight. Durations that feed rates and offsets continue on the scientific calculator.

References

BIPM, The International System of Units (SI Brochure), 9th edition — the second as the SI base unit, defined by the caesium-133 hyperfine frequency 9,192,631,770 Hz. bipm.org （访问日期：2026-09-30）
NIST Special Publication 811, Appendix B.9 — exact factors for the minute (60 s), hour (3,600 s), day (86,400 s) and 365-day year (31,536,000 s). nist.gov （访问日期：2026-09-30）
Wikipedia, Day — the SI day of exactly 86,400 s, and leap seconds that stretch a civil day to 86,401 s. en.wikipedia.org （访问日期：2026-09-30）
Wikipedia, Month — Gregorian months of 28 to 31 days, a mean Gregorian month of 30.436875 days and the synodic month of about 29.53 days. en.wikipedia.org （访问日期：2026-09-30）
Wikipedia, Week — 1 week = 7 days = 168 hours = 10,080 minutes = 604,800 seconds. en.wikipedia.org （访问日期：2026-09-30）