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Consumer Price Index Change Calculator

Work out consumer price index change instantly with clear inputs, formula shown and shareable results.

About Consumer Price Index Change Calculator

A consumer price index is the cost of a fixed basket expressed relative to a base year set to 100. The change in the index is the cumulative inflation since the base, and multiplying by a component's weight approximates how much of that change it contributed.

Formulas

Index value

Index = Current basket cost / Base basket cost x Base index

Cumulative change

Change % = (Index / Base index - 1) x 100

Worked example

With the default values below, Consumer Price Index Change Calculator returns Current index value of 131.20. Change any input above and every figure here is recalculated in your browser.

Inputs used

Cost of the basket in the base year
12,500
Cost of the same basket now
16,400
Base year index value
100
Weight of food in the basket
45

Results

Current index value
131.20
Cumulative price change since the base year
31.20%
Contribution of food to the change
14.04%
Real value of base-year money today
76.22%

Step by step

  1. 1Values used
  2. 2Index value
  3. 3Cumulative change
  4. 4Current index value= 131.20
  5. 5Cumulative price change since the base year= 31.20
  6. 6Contribution of food to the change= 14.04
  7. 7Real value of base-year money today= 76.22

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Indicative estimate only. Fees, entitlements, limits and formulas vary by jurisdiction, statute, policy wording and the facts of the case. This is not legal, tax, insurance or financial advice — confirm with a qualified professional or the relevant authority.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Indicative estimate only. Fees, entitlements, limits and formulas vary by jurisdiction, statute, policy wording and the facts of the case. This is not legal, tax, insurance or financial advice — confirm with a qualified professional or the relevant authority.

Frequently Asked Questions

Why is the basket fixed?

To isolate price change from changes in what people buy. The trade-off is substitution bias, which is why baskets are periodically re-weighted.

What is the difference between CPI and WPI?

CPI measures retail prices faced by households; wholesale or producer indices measure prices at earlier stages and exclude services.

Related Calculators

Consumer Price Index Change Calculator | Calcrivo