What this calculator does
This calculator converts seconds to years or years to seconds, both directions. It is the largest step in the site’s chain of time-unit converters, going straight from the smallest common unit most people convert to the largest, without needing to pass through minutes, hours, days, weeks or months along the way.
The conversion uses a 365.25-day year, which averages in the leap year that occurs roughly every four years, giving 31,557,600 seconds per year (365.25 × 86,400 seconds in a day). It is the same year length used elsewhere on the site for conversions such as days to years.
The formula
Divide seconds by 31,557,600 to get years, or multiply years by 31,557,600 to get seconds. The result also shows the equivalent in days for a more intuitive sense of scale.
| Term | Meaning |
|---|---|
| Year (average) | 365.25 days, or exactly 31,557,600 seconds, averaging in the leap-year day. |
| Seconds | Years multiplied by 31,557,600. |
| Years | Seconds divided by 31,557,600. |
The inputs explained
| Field | What to enter |
|---|---|
| Value | The number to convert, in whichever unit you selected below. |
| Convert | Choose whether you are converting seconds into years, or years into seconds. |
When to use it
Making sense of a large seconds figure
Software, logs and scientific data often report durations in raw seconds; a number like 100,000,000 seconds is far easier to picture once converted to about 3.17 years.
Estimating how many seconds have passed
A quick way to sanity-check a claim like "a billion seconds ago", by converting a chosen number of years into seconds and comparing.
Working with astronomical or scientific time spans
Fields that measure time in seconds at very large scales benefit from a direct seconds-to-years conversion rather than stacking several smaller unit conversions.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Common second values converted to years
A range of large second values and their year equivalents.
| Seconds | Years |
|---|---|
| 1,000,000 s | 0.0317 yr |
| 10,000,000 s | 0.3169 yr |
| 31,557,600 s | 1.000 yr |
| 100,000,000 s | 3.169 yr |
| 500,000,000 s | 15.844 yr |
| 1,000,000,000 s | 31.688 yr |
Common year values converted to seconds
A range of year values and their second equivalents.
| Years | Seconds |
|---|---|
| 1 yr | 31,557,600 s |
| 5 yr | 157,788,000 s |
| 10 yr | 315,576,000 s |
| 18 yr | 568,036,800 s |
| 50 yr | 1,577,880,000 s |
| 100 yr | 3,155,760,000 s |
Questions
How many seconds are in a year?
Using an average 365.25-day year, there are exactly 31,557,600 seconds in a year. A non-leap 365-day year has 31,536,000 seconds instead, so the figure differs slightly depending on which specific year is meant.
How many years is a billion seconds?
One billion seconds is approximately 31.7 years, using the 365.25-day average year.
Why use 365.25 days instead of exactly 365?
Using 365.25 days averages in the extra day added roughly every four years in a leap year, which keeps the conversion accurate over long spans rather than drifting if only 365-day years were assumed.
Is there a smaller time unit converter for weeks or months instead?
Yes. See the site’s weeks to years converter for a smaller step, or the months-to-years and days-to-years converters for other unit pairs in between.
For a smaller step up the same ladder of time units, see the weeks to years converter. For everyday-length durations, see the minutes to hours converter.