What is the Inflation Formula?
The rise in prices of goods and services is referred to as inflation. One of the measures of inflation is the Consumer Price IndexConsumer Price IndexThe Consumer Price Index (CPI) is a measure of the average price of a basket of regularly used consumer commodities compared to a base year. The CPI for the base year is 100, and this is the benchmark point.read more (CPI), and the formula for calculating inflation is:
Where,
 CPI_{x} is Consumer Price Index of Initial Year
 CPI_{x+1 }is Consumer Price Index of next year
In certain cases, we need to calculate the rate of average inflation over a number of years. The formula for the same is:
Where,
 CPI_{x} is Consumer Price Index of Initial Year,
 n is number of years after the initial year,
 CPI_{x+n }is Consumer Price Index of n years after the initial CPI year,
 r is the rate of interest
Table of contents
Key Takeaways
 The inflation formula calculates the rate at which the prices of goods and services have increased in an economy over a year.
 It is typically measured using the Consumer Price Index (CPI), which can be obtained from reports released by the Bureau of Labor Statistics in the USA.
 Inflation is a crucial indicator as it impacts the prices of consumer goods and services, affecting the purchasing power of consumers. What a consumer could buy at a certain price last year might be available at different prices in the current year due to inflation.
Explanation of Inflation Formula
To find out the rate of inflation for one year, follow the given steps:
Step 1: Find out the CPI of the initial year. _{CPIx denotes it.}
Step 2: Find out the CPI of next year. It is denoted by CPI_{x+1.}
Step 3: Calculate the inflation using the formula:
Multiply the above number obtained by 100 if you want the inflation rate in percentage terms.
To find out the average rate of inflation over several years, follow the given steps:
Step 1: Find out the initial CPI.
Step 2: Find out the CPI after n years.
Step 3: Use the following formula to find out the rate of inflationFormula To Find Out The Rate Of InflationThe rate of inflation formula helps understand how much the price of goods and services in an economy has increased in a year. It is calculated by dividing the difference between two Consumer Price Indexes(CPI) by previous CPI and multiplying it by 100.read more denoted by r.
By solving the above equation, we can find out the inflation rate, denoted by r.
Note: Instead of the Consumer Price Index (CPI), some other measures of inflation, such as the Wholesale Price IndexWholesale Price IndexThe Wholesale Price Index tracks the price movement of products in a set territory and wholesaler jurisdiction. Wholesalers provide, manage, and control commodities, usually commonly traded goods, before they are sent to retailers.read more (WPI), may be used. The steps would be the same.
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For eg:
Source: Inflation Formula (wallstreetmojo.com)
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Video Explanation of Inflation
Examples of Inflation Formula (with Excel Template)
Let’s see some simple to advanced examples of the inflation equation to understand it better.
Inflation Formula Example #1
The Consumer Price Index (CPI) for 2016 for a certain country is 147. The CPI for 2017 is 154. Find out the rate of inflation.
Solution:
Use the given data for the calculation of inflation.
Particulars  Amount 

CPI for 2016  147 
CPI for 2017  154 
Calculation of the rate of inflation can be done as follows:
Rate of Inflation = ( 154 – 147 ) / 147
Rate of Inflation will be –
Rate of Inflation = 4.76%
The rate of inflation is 4.76%.
Inflation Formula Example #2
The Consumer Price Index (CPI) for 2010 is 108. The CPI for 2018 is 171. Calculate the average rate of inflation for the years.
Solution:
Use the given data for the calculation of inflation.
Particulars  Amount 

CPI for 2018  171 
CPI for 2010  108 
Calculation of the average rate of inflation can be done as follow:
Here, the number of years (n) is 8.
CPI_{x+n}= CPI_{x} * ( 1 + r )^n
(1+r)^n = 172_{ / 108}
_{1+r = ( 172 }_{/ 108 }_{)^(1/n)}
_{r = ( 172 }_{/ 108 }_{)^(1/n) – 1}
The average rate of inflation will be –
The average rate of inflation (r)= 5.91%
The average rate of inflation between 2010 and 2018 is 5.91%.
Inflation Formula Example #3
A common household in a country buys three eggs, four loaves of bread, and 2 liters of petrol each week. The prices of these goods for 2017 and 2018 are as under:
Year  Price of 1 Egg  Price of 1 Loaf of Bread  Price of Liter of Petrol 

2017  $4  $2  $2 
2018  $5  $2  $3 
Calculate the rate of inflation for 2018.
Solution:
Calculation of Cost of Basket in 2017 will be –
Cost of Basket in 2017 = $4*3 + $2*4 + $2*2
Cost of Basket in 2017 = $24
Calculation of Cost of Basket in 2018 will be –
Cost of Basket in 2018 = $5*3 + $2*4 + $3*2
Cost of Basket in 2018 = $29
Calculation of the rate of inflation can be done as follows:
Rate of Inflation = ($29 – $24 ) / $24
Rate of Inflation will be –
Rate of Inflation = 0.2083 or 20.83%
The rate of inflation in 2018 is 20.83%.
Inflation Formula Example #4
The prices of certain goods in 2016 and 2017 are as under:
Year  Price of 1 Chicken  Price of 1 Loaf of Bread  Price of 1 Book 

2016  5  1  3 
2017  6  2  4 
A common household in a country buys three chickens, two loaves of bread, and two books in a week. Calculate the rate of inflation in 2017.
Solution:
Step 1: We have to calculate the cost of a basket in 2016.
Cost of Basket in 2016 =5*3+1*2+3*2
Cost of Basket in 2016 = 23
Step 2: We have to calculate the cost of a weekly basket in 2017.
Cost of Basket in 2017 = 6 * 3 + 2 * 2 + 4 * 2
Cost of Basket in 2017 = 30
Step 3: We calculate the rate of inflation in the final step.
Rate of Inflation = ( 30 – 23 ) / 23
Rate of Inflation = 30.43 %
The rate of inflation is 30.43%.
Inflation Formula Calculator
You can use this inflation formula calculator.
CPI_{x+1}  
CPI_{x}  
Rate of Inflation Formula=  
Rate of Inflation Formula= 


Relevance and Uses
 The rate of inflation is an important input in the monetary policyMonetary PolicyMonetary policy refers to the steps taken by a country’s central bank to control the money supply for economic stability. For example, policymakers manipulate money circulation for increasing employment, GDP, price stability by using tools such as interest rates, reserves, bonds, etc.read more framework by central banks. If inflation is too high, it may hike interest rates. If inflation is too low, central banks may lower the inflation rate.
 Intuitively, it may seem that if inflation is negative (known as deflation), it is good for the country. However, this is not true. The deflationaryDeflationaryDeflation is defined as an economic condition whereby the prices of goods and services go down constantly with the inflation rate turning negative. The situation generally emerges from the contraction of the money supply in the economy.read more situation may lead to low growth.
 Having a low inflation rate is considered good for the economy. However, generally, economists may not agree on the ideal inflation rate in the economy.
 If inflation is high and volatile, it creates uncertainty about the future prices of goods and services. High inflation tends to discourage investment. It, in turn, reduces growth in the long run. High inflation may be caused by an increase in the money supply in the economy.
 When inflation is high, the cost of living of the wage earners increases. Hence, wage owners may demand higher wages. It, in turn, may increase the costs of goods and services, leading to more inflation. It may lead to a spiral of higher inflation.
 When inflation is too high, people may be discontented. It may lead to social and political unrest. The value of savings held by households and firms reduces in high inflation. Higher inflation increases the cost of goods produced in the country. It may reduce the export competitiveness of the country.
 The nominal Gross Domestic ProductNominal Gross Domestic ProductNominal GDP (Gross Domestic Product) is the calculation of annual economic production of the entire country's population at current market prices of goods and services generated by four main sources: land appreciation, labour wages, capital investment interest, and entrepreneur profits calculated only on finished goods and services.read more (GDP) of a country is the combination of real GDP and inflation. Thus, if the nominal GDP growth is 10% and the inflation rate is 4%, the real rate of GDP growth is approximately 6%. Thus, the real GDP growth that is widely reported is nothing but net growth.
Frequently Asked Questions (FAQs)
The inflation formula assumes a representative basket of goods, with proportional price changes reflecting the overall cost of living. It assumes no significant changes in consumption patterns and provides a simplified measure of price changes, though it may not fully represent the entire economy.
The inflation formula allows easy comparisons across time and regions, aids policymakers in formulating economic policies, helps businesses and investors in decisionmaking, and enables consumers to plan budgets and adjust purchasing decisions.
The inflation formula measures the percentage change in the general price level, resulting in a positive percentage, indicating an increase in prices. On the other hand, the deflation formula calculates the percentage decrease in the general price level, resulting in a negative percentage, indicating a decrease in prices. Both formulas are used to assess changes in the purchasing power of money and the overall price level.
Recommended Articles
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