1 Choose 0

Combination Calculator
Total items (n)
Items chosen (k)

What is 1 choose 0?

Answer

1 choose 0 is
1

Order doesn't matter, no repeats: 1 way to choose 0 of 1 item.

There is exactly one way: take none.

C(1, 0) = 1! / (0! · 1!)

= 1

0! = 1 (an empty product), so 1! cancels out completely.

Row 1 of Pascal's triangle
k1 choose k
01
11

Row sum: 21 = 2 — all subsets of 1 item.

See Also

FAQ

What is 1 choose 0?

1 choose 0 is 1

Why is 1 choose 0 the same as 1 choose 1?

Every way to choose 0 of 1 item leaves exactly 1 behind, so choosing 0 and choosing which one to leave out are the same count: 1 choose 0 = 1 choose 1 = 1. In the formula n! / (k! (n − k)!) the two factorials below just swap places.

How many ways are there if order matters?

The same 1: with 0 chosen items there is only one order, so P(1, 0) = 1 choose 0 = 1. Order starts to matter from 2 items on: n × (n − 1) arrangements.