Fibonacci number

This calculator returns a Fibonacci number from the Fibonacci series for the given index. Enter the index you are looking for and click the 'Calculate' button.

Formula of the Fibonacci function

The Fibonacci sequence is the infinite sequence of numbers which either begins with the double number 1 or is more often provided with a leading number 0. The sum of two consecutive numbers results in the following number:

1, 1, 2, 3, 5, 8, 13,...

The formula calculates the Fibonacci number at the index from a series with a leading number 0. The above calculator also used this formula.

0, 1, 1, 2, 3, 5, 8, 13,...

\(\displaystyle F_n=\frac{(1+\sqrt{5})^n-(1-\sqrt{5})^n}{2^n\sqrt{5}} \)