If you’ve estimated with Planning Poker, you may very well have used cards with either the Fibonacci sequence, or a modified Fibonacci sequence.

The traditional Fibonacci sequence is 1, 2, 3, 5, 8, 13, 21 and so on, with each number the sum of the preceding numbers.

Years ago I began having teams estimate with a modified Fibonacci sequence of 1, 2, 3, 5, 8, 13, 20, 40 and 100.

Why?

It’s because numbers that are too close to one another are impossible to distinguish as estimates.