The real value, also called the purchasing power, is the nominal value adjusted for inflation and measures that value in terms of another item.
The famous Fisher equation captures the relationship between nominal and real value (or interest rate) under inflation:
Real value = Nominal value - Inflation rate
For example, if nominal gross domestic product (GDP) growth rate is 5.5% for a given year and the related annual inflation rate is 2%, then the real GDP growth rate for the year is 3.5%.