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Fibonacci Calculator

n-th Fibonacci number, with neighbors and partial sum.

Compute the n-th Fibonacci number F(n), its neighbors F(n−1) and F(n+1), and the running sum of the first n terms.

Daniel Oh By Daniel Oh
Published Last reviewed 1 min read

Inputs

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

F(0) = 0, F(1) = 1, F(n) = F(n−1) + F(n−2). Ratios F(n)/F(n−1) approach the golden ratio φ ≈ 1.61803.

In depth

Compute the n-th Fibonacci number F(n), its neighbors F(n−1) and F(n+1), and the running sum of the first n terms.