Inflation Calculator (CPI-U)

Use this inflation calculator to convert a US dollar amount from one month to another using the CPI-U price index, so you can compare buying power over time. You can also compare an actual end price to the CPI-expected price to see if it rose faster or slower than inflation.

Amount in start date dollars (USD)

Enter the money amount you want to adjust for inflation. Example: 50 means $50.

Start date (month and year)

Pick the month and year the amount is from. CPI is published monthly, so month matters.

End date (month and year)

Pick the month and year you want to convert to. Must be the same or later than the start date.

CPI data mode

Choose where CPI values come from. Published mode uses stored BLS data only. Select modeled missing months explicitly for estimates, or enter CPI manually.

Series: CPI-U, US city average, all items, not seasonally adjusted.

Advanced options

Manual CPI override (only used in Manual CPI entry mode)

Start CPI (manual override, CPI-U index)

Optional. If you select manual CPI mode, enter the CPI index for the start month. This must use the same CPI series as the end CPI.

End CPI (manual override, CPI-U index)

Optional. If you select manual CPI mode, enter the CPI index for the end month.

Compare to an actual end-date price

Compare to an actual end-date price?

Choose Yes if you also know what the item actually cost in the end date, so we can compare it to what CPI would predict.

Display options

Rounding for money outputs

Choose how to round displayed dollar results. This changes display only, not the underlying math.

Show year-by-year breakdown

Choose Yes to see a simple table of each year: CPI and the inflation-adjusted value at that point (using the same starting amount).

CPI coverage helper (built-in mode)

Suggest nearest covered months if a month is missing?

If built-in CPI cannot be used for your month, this suggests the nearest available month in the table. It does not change your inputs automatically.

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How to use our Inflation Calculator (CPI-U, Month to Month)

Enter the amount in start date dollars (USD), like 100 for $100.
Choose the start date (month and year).
Choose the end date (month and year). It must be the same as or later than the start date.
Pick a CPI data mode: use the built-in CPI table (recommended) or manual CPI entry.
If you want, open Advanced options and turn on "Compare to an actual end-date price?" to compare an item price to CPI.
If using manual CPI mode, enter Start CPI and End CPI (both must be positive and from the same CPI series).
If comparing, enter the actual price in end date dollars (USD).
Optional: choose a rounding mode for money outputs and whether to show a year-by-year breakdown.
Click Calculate to see the inflation-adjusted amount, total inflation percent, and average annual inflation rate.

Definitions

CPI (Consumer Price Index): A price index, which is a number that tracks average prices for a typical basket of goods and services over time.[3]

CPI-U: The CPI series for All Urban Consumers (US city average). This calculator uses the "all items" CPI-U index.[1]

Not seasonally adjusted: CPI values that are not smoothed to remove regular seasonal patterns, so they match the published monthly index used for inflation adjustments.

Inflation-adjusted amount: The dollar amount in the end date that has the same buying power as the start amount, based on CPI.

Inflation factor: End CPI divided by start CPI. Multiply the start dollars by this factor to convert to end-date dollars.

Total inflation (percent): The percent change in CPI from start to end. It can be negative during deflation.

Average annual inflation rate (compound): A single yearly rate that would grow the start CPI to the end CPI over the same time span, using compounding.

Methodology

The calculation uses the CPI-U, US city average, all items, not seasonally adjusted (BLS series CUUR0000SA0). Stored monthly values were downloaded from BLS on 13 September 2026 and run from January 1913 through August 2026, excluding missing observations.

Adjusted amount = starting amount * end CPI / start CPI

Total inflation is (end CPI / start CPI - 1) * 100%. The annualized rate uses the number of months between dates. For December 2024 to December 2025, CPI changes from 315.605 to 324.054: $100 becomes about $102.68.

Published mode rejects missing months. Manual mode uses the entered positive CPI values. Modeled mode explicitly permits interpolation between stored months and trend extrapolation outside the table; such results are labelled estimates and are not BLS observations.

BLS monthly CPI source data

This tool adjusts money between two months using the CPI-U "all items" index (US city average, not seasonally adjusted).[1][3]

Step 1: Get the CPI for each month

If you choose Built-in CPI table, the calculator looks up the CPI index for your start month and end month.

If you choose Manual CPI entry, you must enter Start CPI and End CPI yourself. Both CPI values must be positive, and they must be from the same CPI series (otherwise the comparison is not valid).[1]

Step 2: Time between dates (months)

months_between = (end_year - start_year) * 12 + (end_month - start_month)

If the end date is earlier than the start date, the calculator stops and shows an error. If both dates are the same month, months_between is 0.

Step 3: Inflation factor and inflation-adjusted amount

inflation_factor = cpi_end / cpi_start

amount_end = amount_start * inflation_factor

If cpi_start is 0 or negative (or missing), the calculator stops and shows an error because division would be invalid.

Step 4: Total inflation over the period

total_inflation_percent = (inflation_factor - 1) * 100

This can be negative if prices fell overall between the two months (deflation).

Step 5: Average annual inflation rate (compound)

avg_annual_inflation_rate = ((inflation_factor)^(12 / months_between) - 1) * 100

If months_between = 0, the calculator sets avg_annual_inflation_rate to 0% because you are comparing the same month to itself.

Optional: Compare an actual end price to CPI

This section is only computed if you set "Compare to an actual end-date price?" to Yes and you enter an actual end price.

expected_end_price_from_cpi = amount_start * inflation_factor

price_vs_cpi_difference = actual_end_price - expected_end_price_from_cpi

price_vs_cpi_percent = (price_vs_cpi_difference / expected_end_price_from_cpi) * 100

If expected_end_price_from_cpi is 0 (not expected when amount_start and CPI values are positive), price_vs_cpi_percent is shown as N/A to avoid divide-by-zero.

Notes on interpretation

CPI is an average basket. Your personal inflation can be different if you buy different things than the typical basket.[3]