# What formula is used to calculate the age of the universe?

##### 1 Answer

Use Hubble constant relationship to time, i.e.:

substitute an estimate for Hubble constant

convert to years

but be carefully there are 5 cases:

1) Non-zero cosmological Constant (yes that Einstein cosmos constant):

2) Empty Universe model (no mass):

3) Open:

4) If the universe has exactly the right amount of mass, it will neither stop expanding, nor re-contract either. This model is referred to as the “critical universe”:

5) Open Model:

Typically what you will hear is the universe is 13.8 billion years old, that is