Write the first two terms of the Fibonacci sequence, which are 0 and 1.
Calculate the third through 15th terms in the Fibonacci sequence by adding the last number in the sequence to the previous number in the sequence. For example, 1 plus 0 equals 1, which is the third term. 1 plus 1 equals 2, which is the fourth term. The first 15 terms are 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233 and 377.
Divide any term in the sequence that is the 11th term or higher by the previous term in the sequence to calculate the ratio 1.618. For example, divide the 11th term, which is 55, by the 10th term, which is 34, to get 1.61798, which rounds to 1.618; 55 divided by 34 also equals 1.61798, or 1.618.
Divide any term in the sequence that is the ninth term or higher by the next term in the sequence to calculate the ratio 0.618. For example, divide the ninth term, which is 21, by the 10th term, which is 34, to get 0.6176, which rounds to 0.618; 21 divided by 34 also equals 0.6176, or 0.618.