Years to Days Converter
Convert years to days — using the average Gregorian year of 365.2425 days. Results update as you type; exact factors shown.
One year (365.2425 days) is 365.2425 days — see the exact factor, not a rounded rule of thumb.
How the years to days converter works
Time converts through the second. Minutes, hours, days and weeks are exact multiples. A month is taken as the Gregorian average (30.436875 days) and a year as the Gregorian average (365.2425 days = 31,556,952 s); calendar months and leap years vary from these averages.
The UK is metric for most trade and science but keeps miles, pints, stone and mpg (with the imperial gallon) in daily life.
Common time conversions
| From | To | Units |
|---|---|---|
| 0.25 yr | 91.3106 d | year (365.2425 days) to days |
| 0.5 yr | 182.6213 d | year (365.2425 days) to days |
| 1 yr | 365.2425 d | year (365.2425 days) to days |
| 2 yr | 730.485 d | year (365.2425 days) to days |
| 3 yr | 1,095.7275 d | year (365.2425 days) to days |
| 5 yr | 1,826.2125 d | year (365.2425 days) to days |
| 10 yr | 3,652.425 d | year (365.2425 days) to days |
| 18 yr | 6,574.365 d | year (365.2425 days) to days |
| 21 yr | 7,670.0925 d | year (365.2425 days) to days |
| 50 yr | 18,262.125 d | year (365.2425 days) to days |
| 100 yr | 36,524.25 d | year (365.2425 days) to days |
| 1,000 yr | 365,242.5 d | year (365.2425 days) to days |
Units in this converter and their exact factors
| Unit | Symbol | One unit in seconds |
|---|---|---|
| millisecond | ms | 0.001 second |
| second | s | 1 second |
| minute | min | 60 second |
| hour | h | 3,600 second |
| day | d | 86,400 second |
| week | wk | 604,800 second |
| month (average, 30.4369 days) | mo | 2,629,746 second |
| year (365.2425 days) | yr | 31,556,952 second |
FAQFrequently asked questions about time conversion
How many days in a year?
365 in a common year, 366 in a leap year; the long-run average is 365.2425.
Why the decimal?
Because the Gregorian calendar adds a leap day nearly every four years, skipping three century years in four.
How many days is 18 years?
About 6,574.
Which should I use for an exact age?
Neither — count the actual calendar days with the age calculator.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Physical Laboratory (NPL) — United Kingdom's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.