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Fibonacci number generator
Generate the Fibonacci sequence — F0 = 0, F1 = 1, each term the sum of the two before. BigInt keeps even very large terms exact.
Output · 15 terms
ReadyEach Fibonacci number is the sum of the two before it. The ratio between consecutive terms approaches the golden ratio φ ≈ 1.618. Terms grow fast, so larger indices become very long integers.
A free Fibonacci number generator that lists the first N terms of the Fibonacci sequence, starting from F(0) = 0 and F(1) = 1. Each term is computed with BigInt arithmetic, so even very large terms — F(100) has 21 digits — are exact. Copy the sequence as a comma-separated list or one per line.
How to generate Fibonacci numbers
- Enter the number of terms you want (up to 100).
- The sequence from F(0) onward appears below.
- Use the copy button to export as CSV or a plain list.
How the Fibonacci sequence is defined
The Fibonacci sequence starts with F(0) = 0 and F(1) = 1. Every subsequent term is the sum of the two preceding terms: F(n) = F(n-1) + F(n-2). The numbers grow exponentially — F(100) is 354,224,848,179,261,915,075. Standard JavaScript floating-point loses precision well before that, which is why this generator uses BigInt to keep every digit exact.
Frequently asked questions
What is the Fibonacci sequence?
A sequence where each number is the sum of the two before it: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34 … It appears in nature, mathematics, and computer science algorithms.
Does the sequence start at 0 or 1?
By the most common convention, F(0) = 0 and F(1) = 1, making the sequence 0, 1, 1, 2, 3 … Some sources start at F(1) = 1, F(2) = 1, omitting the leading zero.
How many Fibonacci numbers can I generate?
Up to 100 terms. F(99) is a 21-digit number, computed exactly via BigInt.
What is the golden ratio connection?
The ratio of consecutive Fibonacci terms converges to the golden ratio φ ≈ 1.6180339887. The further along the sequence you go, F(n+1) / F(n) gets arbitrarily close to φ.