Series I Savings Bond Calculator

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Inputs

Initial Investment

$

Interest Rate at Issue

%

Estimated Secondary Interest Rate

%

Estimated Long-Term Inflation Rate

%

Results

Guaranteed 6-Month Balance

$10,345

Guaranteed 6-Month Interest Earned

$345

Estimated 1-Year Balance

$10,564

Estimated 1-Year Interest Earned

$564

Estimated 30-Year Balance

$24,383

Estimated 30-Year CAGR

3.02%

Note: Selling your i bond before five years loses three months of interest (not calculated). Selling before one year forfeits all earned interest.

Estimated 1-Year Changes

Show 1-Year Interest Table

Calculating I Bond Interest Rates

The posted i bond rate is known as the composite or earning rate. This rate is a combination of a fixed and inflation-adjusted rate. The interest rate is calculated as follows:

The inflation rate has a 2x multiple, affecting the i bond rate more significantly than the fixed rate. Continue reading to learn more about the different types of rates and how they impact your return on investment.

Fixed Rate

The fixed rate is issued when you buy the bond and remains the same throughout maturity. For example, if you purchased a bond in November 2022 with a fixed rate of 0.40%, it would stay the same throughout the 30-year maturity.

The fixed rate is announced twice a year on May 1st and November 1st. The announced fixed rate is then valid for i bonds purchased in the next six months. However, after buying the bond, your fixed rate is locked in. The table below highlights the historical fixed rates.

Inflation-Adjusted Rate

The essential part of the i bond rate is the inflation-adjusted rate or variable rate. Combined with the fixed rate, this derives your composite rate.

The inflation rate is based on changes to the Consumer Price Index for all Urban Consumers (CPI-U). When inflation in the United States increases, so does the inflation rate. The i bond yield will also decrease with the inflation rate.

Like the fixed rate, the inflation rate changes every six months on May 1st and November 1st. However, the variable rate is different for the entire bond lifetime.

This interest rate will be valid for six months after buying the bond. Afterward, the variable rate will adjust to the current market inflation rate. The table below highlights the historical inflation rates.

Composite Rate

As mentioned, the composite rate combines the fixed and adjustable rates. The market composite rate changes every six months. However, your effective composite rate changes six months after your purchase date. If the market rate changes earlier, your bond rate will catch up after the half-year period.

The i bond composite equation is mentioned above. As an example, we can calculate the current rate of 6.89% using the 0.40% fixed rate and 3.24% inflation rate.

After purchasing the bond, your composite rate will adjust every six months. For example, if you buy an i bond in January, the rate will change every July 1st and January 1st. If you buy an i bond in February, your rate will adjust every August 1st and February 1st. As such, your composite rate is guaranteed for six months and will then adapt to the current inflation rates.

In some scenarios, the inflation rate will decrease. For example, during periods of deflation, the inflation rate will be negative. This will not turn i bond rates negative. The lowest an i bond rate can drop to is zero.

Calculating I Bond Penalties

• Selling Before One Year: Selling your i bond before 12 months results in the harshest penalty. If this is done, you will lose all accumulated interest. As a result, many investors wait until after the first year to sell their i bonds.

• Selling Before Five Years: After the one-year mark, you will lose three months' interest if you cash out your bond before five years. For example, if you sell your bond after 12 months, you will only receive nine months of interest payments.

• Selling After Five Years: If you hold your i bond for at least five years, there is no penalty. You will receive all accrued interest from the bond upon selling.

Calculating I Bond Taxes

The interest you receive from i bonds is subject to income taxes. However, in most cases, you can avoid state income taxes on the interest earned. Some states offer tax breaks to people who invest in savings bonds, while others do not.

Investors can't avoid federal taxes and must report i bond interest each year on their tax returns. However, this interest can be exempt from federal taxes if it meets certain criteria. You must have used the savings bond to pay for qualified educational expenses such as tuition or books to qualify for savings bond tax exemption.

The Bottom Line

Overall, i bonds are a popular savings vehicle for investors looking to earn inflation-protected interest with low risk and tax-free benefits. Whether you are buying i bonds to save for college or want a safe investment option, they can be a great tool to help meet your financial goals. To maximize your earnings from i bonds, it is essential to understand how their rates work and which tax savings you may be eligible for.