Variable Inflation Calculator
Apply different rates across periods.
Variable Inflation Calculator: Scenario Inputs
Annual percentage rate or benchmark index change.
Inflation & Purchasing Power Analysis
Over 3 years at 3.5% inflation, a $75,000 salary requires $83,154 to retain equal purchasing power. Without matching raises, your real compensation experiences an effective reduction of $7,355 (-9.81%).
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How Variable Inflation Calculator Works?
The Variable Inflation Calculator starts a price index at 100. It applies each period's inflation rate to the prior index value, one period at a time.
Enter the rate sequence
Type one rate per year, quarter or month, in order.
Build the price level
The calculator starts at 100 and multiplies by 1 + rate for each period.
Average the rates
The calculator computes the geometric average and the arithmetic average.
Apply to any amount
Multiply any salary or price by the final price level ÷ 100 to adjust the amount.
Variable Inflation Calculator Formula
The Variable Inflation formula chains period rates into a price level and takes the n-th root for the average rate.
Pn = 100 × Π (1 + rk)
Average % = [(Pn ÷ 100)1/n − 1] × 100
Variables
- rk
- Inflation rate in period k
- n
- Number of periods
- Pn
- Price level after n periods, with 100 at the start
Worked example
Six annual rates of 2.5%, 1.8%, 1.2%, 4.7%, 8.0% and 4.1% lift the price level from 100 to 124.30. The geometric average is 3.69%, and the arithmetic average is 3.72%.
Variable Inflation Calculator Conversion Table
This table builds a price level from 6 variable annual rates.
| Period | Rate | Price level (start = 100) | Geometric average so far |
|---|---|---|---|
| Year 1 | 2.5% | 102.50 | 2.50% |
| Year 2 | 1.8% | 104.35 | 2.15% |
| Year 3 | 1.2% | 105.60 | 1.83% |
| Year 4 | 4.7% | 110.56 | 2.54% |
| Year 5 | 8.0% | 119.41 | 3.61% |
| Year 6 | 4.1% | 124.30 | 3.69% |
What is Variable Inflation Calculator?
The Variable Inflation Calculator is a tool that combines different inflation rates across periods into a cumulative price level and one average rate. The calculator focuses on prices, not on a single salary, so the output describes the inflation path itself.
The calculator reports both the geometric average rate and the simple arithmetic average. The geometric average is the correct rate for compounding.
What are the uses of Variable Inflation Calculator?
There are 4 main uses of the Variable Inflation Calculator.
Summarize uneven inflation
Reduce a volatile run of rates to one correct average rate.
Build custom indexes
Create a price-level series from forecast or historical rates.
Compare inflation episodes
Contrast a calm period with a volatile period by price level and average rate.
Fix averaging errors
Show the gap between arithmetic and geometric averages in analysis work.
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