To convert femtoseconds to years, multiply by 3.168808781e-23. That factor is the whole relationship: both units measure time, so the conversion is a proportion with no offset and no substance-specific constant.
The Julian year of 365.25 days used in astronomy and engineering. One quadrillionth of a second, the timescale of chemical bonds breaking.
Months and years are not fixed. This page uses the average Gregorian month of 30.44 days and the Julian year of 365.25 days, which is right for durations and wrong for calendars: three months from 31 January is not 91.31 days in any useful sense. Use a date calculator for calendar arithmetic. Below the calculator there is a step table for the values people look up most, and a second table putting real time figures into years so the number you get has something to be compared against.
The formula
femtoseconds- The amount you are converting, in femtoseconds
3.16880878140e-23- The exact number of years in one femtosecond
years- The converted result
How it works, step by step
- Enter the value in femtoseconds.
- It is multiplied by 3.16880878140e-23, the exact factor between the two units.
- The answer is shown in years, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A larger figure: 100 fs in years
At 100 fs (a larger figure), the same quantity in years is 100 × 3.16881e-23 = 3.16881e-21 yr. One femtosecond is 3.16881e-23 years, so the numbers shrink as expected.
A round figure: 1 fs in years
A round figure comes to about 1 fs. Multiplying by the factor: 1 × 3.16881e-23 = 3.16881e-23 yr. Dividing the answer back by 3.16881e-23 returns the figure you started with, which is the quickest way to check you have the factor the right way up.
How to read your score
Frequently asked questions
How many years are in one femtosecond?
Exactly 3.16880878140e-23. Every figure on this page is that one number multiplied by your input, so the only rounding is at the display step.
What is the formula to convert femtoseconds to years?
years = femtoseconds × 3.16880878140e-23. Reversed, femtoseconds = years ÷ 3.16880878140e-23, which is the same as multiplying by 3.15576000000e+22.
Which is the bigger unit, the femtosecond or the year?
The year. One femtosecond is only 3.16881e-23 of a year, so it takes 3.15576e+22 femtoseconds to make one year.
What does this quantity actually measure?
Both units measure time. That is why a single factor is enough: there is no temperature offset and no material property involved, unlike conversions that cross between different quantities.
What is a femtosecond?
One quadrillionth of a second, the timescale of chemical bonds breaking.
What is a year?
The Julian year of 365.25 days used in astronomy and engineering.
Why does my answer differ from another converter?
Almost always because the other tool rounded the factor before multiplying. This page keeps full double precision through the calculation and rounds only for display, and it prints the factor it used so you can see where any difference came from.
Femtoseconds to years reference tables
| Femtoseconds | Years |
|---|---|
| 0.5 fs | 1.58440e-23 yr |
| 1 fs | 3.16881e-23 yr |
| 2 fs | 6.33762e-23 yr |
| 3 fs | 9.50643e-23 yr |
| 5 fs | 1.58440e-22 yr |
| 10 fs | 3.16881e-22 yr |
| 20 fs | 6.33762e-22 yr |
| 25 fs | 7.92202e-22 yr |
| 50 fs | 1.58440e-21 yr |
| 75 fs | 2.37661e-21 yr |
| 100 fs | 3.16881e-21 yr |
| 250 fs | 7.92202e-21 yr |
| 500 fs | 1.58440e-20 yr |
| 1000 fs | 3.16881e-20 yr |
| 5000 fs | 1.58440e-19 yr |
Exact factor: 1 femtosecond = 3.16880878140e-23 years.
| Quantity | fs | yr |
|---|---|---|
| A camera flash | 1e+12 fs | 3.169e-11 yr |
| A heartbeat | 8.57e+14 fs | 2.716e-08 yr |
| A pop song | 2.100e+17 fs | 6.654e-06 yr |
| A working day | 2.880e+19 fs | 0.0009126 yr |
| A pregnancy | 2.419e+22 fs | 0.7666 yr |
| A mortgage term | 7.574e+23 fs | 24 yr |
Published reference values, converted with the same factor this page uses.