Tom's Inflation Calculator
Frequently Asked Questions


Note: There are two versions of Tom's Inflation Calculator—one written in Java and another written in JavaScript. The two versions have several differences. Most questions in this FAQ pertain to both versions, but some pertain to one version or the other, as noted below.

What is the difference between the Java and JavaScript versions of Tom's Inflation Calculator?

What can Tom's Inflation Calculator do, and what can't it do?

Why won't the calculator run on my computer?

How can I use the calculator to convert wages and prices from past years into equivalent dollar amounts today?

How can I use the calculator to convert today's wages and prices into equivalent dollar amounts for past years?

How can I use the calculator to forecast future inflation?

What does the "Options" button in the Java version do?

What does the "Show Rates" button in the Java version do?

What is the "cumulative inflation rate" in the Java version?

Why don't the calculator's inflation rates match the rates I've seen elsewhere?

Why are the medical-cost inflation rates much lower than the rates I've seen elsewhere?

What is the source of data that the calculator uses?

What if I don't trust the government's official inflation data?

Why do I sometimes see an error message in the Java version that says "Answer Too Large"?

Why can't the calculator adjust inflation for different months during the same year?

Why doesn't the calculator include the starting year when making calculations?

Where can I send feedback about Tom's Inflation Calculator?  


What is the difference between the Java and JavaScript versions of Tom's Inflation Calculator?

Technically, one version is written in the Java programming language and the other is written in the JavaScript language. (Despite their similar names, they are very different programming languages.) To run
the Java version, most web browsers require users to download and install Oracle's Java Runtime Environment. It's free but is incompatible with some browsers, and some people prefer not to install it. The JavaScript version rarely requires a plug-in because almost all popular browsers support it as a standard feature.

Functionally, the two versions of the Inflation Calculator have several differences. Apart from appearances, the main difference is that the Java version includes five data sets, whereas the JavaScript version has only two. Both calculators default to the Consumer Price Index for All Urban Consumers (CPI-U, Annual Average). The Java version also has the Consumer Price Index (CPI) for Urban Wage Earners and Clerical Workers (CPI-W), U.S. Medical Cost Inflation (a CPI component), CPI-U (December to December instead of Annual Average), and ShadowStats (a private-sector source). But the JavaScript version has a data set not found in the Java version: the Social Security Wage Index. Another difference is that the Java version can display all the annual inflation rates in each data set.

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What can Tom's Inflation Calculator do, and what can't it do?

Tom's Inflation Calculator converts U.S. dollars between two different years, adjusting the dollars for inflation (or deflation). Over time, wages and prices tend to rise, making direct comparisons between two years difficult. Past prices seem cheaper, but past wages were lower, too. Today's inflated dollars just don't buy as much stuff as past dollars did. Tom's Inflation Calculator adjusts for these differences, allowing you to make roughly equivalent comparisons of wages and prices between two years.

It's not an investment calculator. You can't use it to calculate how an investment will grow over time. However, you can use it as a companion with an investment calculator. First, use the investment calculator to estimate how large your savings will grow in the future. Then use the Inflation Calculator to estimate the actual purchasing power of that sum, as expressed in today's dollars. (See: How can I use the calculator to forecast future inflation?)

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Why won't the calculator run on my computer?

The original version of Tom's Inflation Calculator is a special type of computer program known as a Java applet. When you view the Inflation Calculator page in your web browser, the applet should download and run automatically. (Downloading takes a few moments, depending on the speed of your Internet connection.) If the applet doesn't run, the most common reason is that Java isn't installed on your computer. Try downloading and installing the latest version of Oracle's Java Runtime Environment. If you download Java from that source, it's free and will not put malware or spyware on your computer.

If Java is already installed but the applet still doesn't run, another common problem is that Java has been disabled for security reasons. Java applets are almost always safe to run, but some browsers (especially on corporate PCs) enforce higher security settings. When using Microsoft Internet Explorer, pull down the Tools menu and select Internet Options. Click the Security tab, then click the Custom Level button. Under the Java VM section, select "High safety." This should allow the Java applet to run while preserving strong security.

Another potential problem is that Java is installed but isn't registered with the web browser. With Internet Explorer, pull down the Tools menu and select Internet Options. Click the Advanced tab. Scroll down and check the box labeled "Use JRE 1.6.0_15 for [applet] (requires restart)." (The Java version number may be different on your system.) You must restart Internet Explorer for this change to take effect.

Another alternative is to bypass the Java version of the calculator and use the JavaScript version instead. Almost all web browsers will run it without installing any plug-ins, unless scripts are disabled in the browser for strict security reasons. The two versions of the calculator are similar but have a few differences, as noted above.

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How can I use the calculator to convert wages or prices from past years into equivalent dollar amounts today?

Type the wage or price from a past year into the Dollar Amount field. Type the year for that wage or price into the Starting Year field. Type the current year into the Target Year field. (Note: some data sets don't allow you to target the current year because the inflation data isn't available yet; the default data set uses a forecast for the current year.) Now click the Calculate button. The answer appears in the Converted Amount field.

For example, let's say you were making $25,000 a year in 2000. Have your wages kept pace with price inflation since then?

  • To find out, start with the default data set (U.S. Price Inflation, CPI-U, Annual Average):

  • Enter 25,000 in the Dollar Amount field.

  • Enter 2000 in the Starting Year field.

  • Enter 2014 in the Target Year field.

  • Click the Calculate button.

The answer—in this case, $34,447.86—appears in the Converted Amount field. If your current salary is less than that amount, you haven't kept up with general price inflation. Time for a raise!

If you are a clerical or hourly-wage worker, you can repeat this calculation using the alternative CPI-W data, which attempts to track your typical purchases more closely. (This data set is available only in the Java version of the calculator.) Click the Options button to choose "U.S. Price Inflation (CPI-W)", then click OK. Next, change the target year to 2013, because the government has not yet released inflation data for 2014. (The previous example used forecast data for 2014.) Now click the Calculate button again. The answer should be $33,964.97.

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How can I use the calculator to convert today's wages and prices into equivalent dollar amounts for past years?

Type the wage or price from this year into the Dollar Amount field. Type this year into the Starting Year field. (Note: some data sets don't allow you to start with the current year because the inflation data isn't available yet; the default data set uses a forecast for the current year.) Type the past year to which you want to convert this wage or price into the Target Year field. Click the Calculate button. The answer appears in the Converted Amount field.

For example, suppose you just paid $3.50 for a gallon of regular gasoline. Somebody tells you that gasoline cost only 50 cents a gallon in 1975. But was gasoline really cheaper back then, after allowing for inflation?

  • To find out, use the default data set: U.S. Price Inflation (CPI-U, Annual Average). The currently selected data set is always indicated below the row of Inflation Calculator buttons. You can change it by clicking the Options button.

  • Enter 3.50 in the Dollar Amount field.

  • Enter 2014 in the Starting Year field.

  • Enter 1975 in the Target Year field.

  • Click on the Calculate button.

The answer—in this case, $0.79—appears in the Converted Amount field. Of course, 79 cents is more than 50 cents, so the $3.50 gasoline you bought in 2014 is indeed more expensive than the 50-cent gasoline in 1975, after adjusting for inflation.

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How can I use the calculator to forecast future inflation?

Choose this data set: "U.S. Price Inflation (CPI-U, Annual Average)." It's the only data set with forecasts of inflation rates into the future. It's also the default data set when the Inflation Calculator first runs. (In the Java version of the calculator, the active data set is always indicated by the label below the row of buttons at the bottom of the calculator. In the JavaScript version, the selection buttons indicate the active data set.)

You can use this data set to estimate the effects of inflation as far forward as the year 2100. Of course, these forecasts are speculation. For the current year through 2023, the forecasts are from the Congressional Budget Office, a nonpartisan source. After that, the calculator automatically computes the mean average inflation rate since the U.S. government began gathering these statistics in 1913. In 2014, that average annual rate is 3.321%.

If you have used someone else's investment calculator to estimate how your savings will grow, you can enter those amounts into my Inflation Calculator to estimate the inflation-adjusted value of those future dollars. (My thanks to Penelope Reznor and Kodi Wolf for suggesting this feature.)

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What does the "Options" button in the Java version do?

This button lets you change the inflation data that the calculator uses for its arithmetic. It also lets you change the appearance of answers in the Converted Amount field by turning dollar-and-cents formatting on or off. The default setting is on.

Clicking on the Options button opens the Inflation Calc Options window. Here, you can choose from five different data sets. When the calculator first runs, the default data set is "U.S. Price Inflation (CPI-U, Annual Average)." Use this data to see how inflation is affecting the retail prices of goods and services.

Another data set is "U.S. Price Inflation (CPI-W)." If you are a clerical or hourly-wage worker, this data is supposed to reflect your purchases more accurately.

All data sets let you perform calculations forward or backward in time, for any years within the range of their data.

For most purposes, the default "U.S. Price Inflation (CPI-U, Annual Average)" data set is sufficient. The others are more specialized. Below is more information about them:

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