Last updated: 2026-05-14

Time unit

A time unit is a standardized duration used to measure intervals. While the second is the SI base unit, everyday and scientific work involves a wide range of units — from milliseconds in computing to years in history and astronomy.

The units covered

Milliseconds (ms) — one thousandth of a second. The standard unit for computer response times, network latency, and audio processing. A human blink takes roughly 100–400 ms.

Seconds (s) — the SI base unit, defined since 1967 by the hyperfine transition frequency of caesium-133 (9,192,631,770 cycles per second). All other time units in this converter are exact multiples of the second.

Minutes (min) — exactly 60 seconds. A historical convenience unit whose 60-base also dates to Babylonian mathematics.

Hours (h) — exactly 3,600 seconds (60 × 60). The division of the day into 24 hours comes from ancient Egypt and Mesopotamia.

Days (d) — exactly 86,400 seconds. One mean solar day — the average time for the Earth to complete one rotation relative to the Sun.

Weeks (wk) — exactly 604,800 seconds (7 × 86,400). The 7-day week is found across many ancient cultures and is now the global standard.

Months (mo) — this converter uses the average Gregorian month: 365.2425 ÷ 12 ≈ 30.4369 days (2,629,746 seconds). Calendar months vary from 28 to 31 days; the average is the only single value that works for a unit converter.

Years (yr) — this converter uses the average Gregorian year: 365.2425 days (31,556,952 seconds). The Gregorian calendar's leap-year rule (÷4 yes, ÷100 no, ÷400 yes) produces this average.

Conversion table

From	To seconds
1 ms	0.001
1 min	60
1 h	3,600
1 day	86,400
1 week	604,800
1 month	2,629,746
1 year	31,556,952

How to use this calculator

Enter any value in any field — the remaining units update immediately. For example, entering 1 in the Years field shows that one year contains approximately 365.24 days, 8,765.8 hours, 525,949 minutes, and 31,556,952 seconds.

Frequently Asked Questions (FAQ)

How many seconds are in a day?

There are exactly 86,400 seconds in a standard day (24 hours × 60 minutes × 60 seconds). However, on days when a leap second is inserted by the International Earth Rotation Service, the day has 86,401 seconds. For everyday calculations, 86,400 is the correct figure.

Why is a year not exactly 365 days in this converter?

This converter uses the average Gregorian year of 365.2425 days (31,556,952 seconds). The Gregorian calendar adds a leap day every 4 years, skips it every 100 years, but adds it back every 400 years, producing that average. For precise astronomical work, the Julian year (365.25 days) or the tropical year (365.2422 days) may be more appropriate.

Why does the month value differ from 30 days?

Calendar months vary from 28 to 31 days. This converter uses the average Gregorian month of 365.2425 ÷ 12 ≈ 30.436875 days (2,629,746 seconds). If you need exactly 30 days, multiply the day value by 30 directly.

How many seconds are in a year?

Using the Gregorian average: 365.2425 × 24 × 60 × 60 = 31,556,952 seconds. The more commonly cited figure of 31,536,000 seconds assumes exactly 365 days.