**5.4. The amount of inflation**

The amount of inflation is normally specified by the logarithm of the amount
of expansion, *the number of e-foldings* *N*, given by

(46)
(47)

where the final step uses the SRA. Notice that the amount of inflation
between two scalar field values can be calculated without needing to solve
the equations of motion, and also that it is unchanged if one multiplies
*V*() by a constant.

The minimum amount of inflation required to solve the various
cosmological problems is about 70 *e*-foldings, i.e. an
expansion by a
factor of 10^{30}. Although this looks large, inflation is typically
so rapid that most inflation models give much more.