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.
Australia is fully metric under the National Measurement Act 1960; imperial units appear only in trade with the US and in older documents.
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 Measurement Institute (NMI) — Australia's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.