Years and days
A year here is the Gregorian average of 365.2425 days, which accounts for leap years. Ages, contracts, depreciation and long-term interest are counted in years.
A day here is 24 hours, or 86,400 seconds; it ignores the rare leap second. Deadlines, rental periods, shipping times and interest calculations are counted in days.
Worked example
Convert 2 yr: 2 × 365.2425 = 730.485, so 2 years is 730.485 days. Likewise 5 yr = 1,826.2125 d.
Estimating in your head
Multiply by 370 for a quick figure; it is off by about 1.3%. For 2 yr that gives 740 d, against 730.485 exactly.
Going the other way
To convert days to years, divide by 365.2425 (or multiply by 0.00273790700699).
How this works
d = yr × 365.2425
1 yr = 31,556,952 s and 1 d = 86,400 s, both by definition, so the factor is their ratio: 365.2425 exactly. Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.
Frequently asked
How many days are in a year?
1 year = 365.2425 days, exactly. The value follows from the unit definitions, so it never changes.
How do I convert years to days?
Multiply by 365.2425. For example, 5 yr × 365.2425 = 1,826.2125 d.
What is 10 yr in days?
10 yr = 3,652.425 d. The table next to the converter lists more common values.
Is the result rounded?
Only on screen. The page computes with the exact definitions and removes floating-point noise past 15 significant digits; pick 3 to 12 significant figures, or use Copy result for the full value.
Sources
- BIPM — The International System of Units (SI Brochure), 9th edition
- NIST SP 811 Appendix B.8 — Factors for units listed alphabetically
- Wikipedia — Gregorian calendar
Reviewed Oct 17, 2026 · test vectors fixtures/units/time/years-to-days/