THE NUMORIX GUIDE
How to use the Inflation calculator
Last reviewed September 14, 2026
What this calculator does
Historical mode multiplies the entered amount by destination-year CPI divided by source-year CPI.
Formula and method
Historical mode multiplies the entered amount by destination-year CPI divided by source-year CPI. The engine's annual CPI table runs from 1913 through 2024. The forward flat-rate mode applies amount x (1 + rate)^years, while the backward mode divides by that same factor to express a future amount in earlier purchasing-power terms.
Variables and inputs
Use amount, source year, destination year, a flat annual inflation rate, and years for the theoretical forward or backward tools. Historical years are selected from the CPI table; rates are percentages and the amount is currency.
Worked example
For $100 in 2000 expressed in 2024 dollars, the engine uses CPI 172.2 and 313.689: 100 x 313.689 / 172.2 = about $182.17. At a flat 3% rate for 10 years, $100 becomes 100 x 1.03^10 = about $134.39.
How to interpret the result
The historical result describes the change in the average CPI basket represented by the table, not the exact price of one household's purchases. A forward result is a constant-rate scenario. The displayed percentage change is the ratio of the modeled equivalent to the original amount.
Common mistakes to avoid
Use the source year as the denominator and the destination year as the numerator. Do not use a current partial-year figure as though it were a completed annual average. Keep a historical CPI comparison separate from a personal inflation estimate.
Assumptions and limitations
The table is annual and uses the values embedded in the route; it does not model monthly CPI, regional indexes, category-specific prices, quality changes, taxes, or household substitution. The flat-rate tools are mathematical projections, not official forecasts.