Estimate the future value of your Series I Savings Bonds. Calculate composite rates, total interest earnings, and see how inflation protection grows your investment over time.
📋 Quick Rate Presets (recent historical rates):
You buy the maximum $10,000 in electronic I-Bonds with the current fixed rate of 1.30% and an inflation rate of 1.48%.
Composite Rate: 1.30 + (2 × 1.48) + (1.30 × 0.0148) = 4.28%
After 5 years: ~$12,333 (no penalty)
After 30 years (maturity): ~$35,157
Interest compounds semi-annually. Federal tax deferred until redemption.
A parent buys $5,000 in I-Bonds when their child is born, with a fixed rate of 0.90% and inflation rate of 1.69%.
Composite Rate: 0.90 + (2 × 1.69) + (0.90 × 0.0169) = 4.30%
After 18 years: ~$10,620
If used for qualified education expenses, the interest may be tax-free. I-Bonds are a popular choice for college savings alongside 529 plans.
An investor bought $10,000 in I-Bonds in May 2022 when the fixed rate was 0.00% and the inflation rate was 4.81% (the highest in I-Bond history).
Composite Rate: 0.00 + (2 × 4.81) + (0) = 9.62%
After 1 year: ~$10,962 (after 3-month penalty: ~$10,722)
This was the highest composite rate in I-Bond history. Rates adjust every 6 months based on CPI-U inflation data.
You buy $2,000 in I-Bonds with a composite rate of 4.00% and redeem after 3 years.
Value before penalty: ~$2,252
3-month penalty: ~$22
Value after penalty: ~$2,230
If you redeem before 5 years, you lose the last 3 months of interest. After 5 years, there is no penalty.
A Series I Savings Bond (I-Bond) is a U.S. Treasury security that earns interest based on a combination of a fixed rate and an inflation rate. The interest rate is adjusted every six months based on changes in the Consumer Price Index for All Urban Consumers (CPI-U).
You earn a full month's interest regardless of when in the month you buy. Buying near the end of the month maximizes your effective return.
The fixed rate is announced every May 1 and November 1. If you expect rates to rise, you may want to wait. If you expect them to fall, lock in early.
I-Bonds are one of the few investments that guarantee your principal keeps pace with inflation. The inflation component ensures you never lose purchasing power.
If you use I-Bonds for qualified higher education expenses, the interest may be completely tax-free (subject to income limits). Form 8815 is used to claim this exclusion.
Series I Savings Bonds (I-Bonds) are low-risk U.S. Treasury savings bonds designed to protect your money from inflation. Unlike traditional bonds that pay a fixed rate, I-Bonds earn interest based on two components: a fixed rate that stays the same for the life of the bond, and an inflation rate that adjusts every six months based on the Consumer Price Index (CPI-U).
I-Bonds were introduced in 1998 and have become increasingly popular as a way to preserve purchasing power. They are backed by the full faith and credit of the U.S. government, making them one of the safest investments available. The interest earned is exempt from state and local income taxes, and federal taxes can be deferred until you redeem the bond or it reaches maturity.
The bonds earn interest for up to 30 years from the date of purchase. You cannot redeem I-Bonds within the first year. If you redeem between 1 and 5 years, you forfeit the last 3 months of interest as a penalty. After 5 years, there is no penalty for redemption.
The composite rate for I-Bonds is calculated using a formula set by the U.S. Treasury. The formula combines the fixed rate and the semiannual inflation rate:
Example: If the fixed rate is 1.30% (0.0130) and the semiannual inflation rate is 1.48% (0.0148):
Composite Rate = 0.0130 + (2 × 0.0148) + (0.0130 × 0.0148)
= 0.0130 + 0.0296 + 0.0001924
= 0.0427924
= 4.28% (rounded)
The inflation rate is determined by changes in the non-seasonally adjusted Consumer Price Index for All Urban Consumers (CPI-U) over a six-month period. The Treasury announces new rates every May 1 and November 1. Once set, your composite rate applies for the next six months.
I-Bond interest compounds semi-annually. This means that every six months, the interest earned is added to the principal, and future interest is calculated on the new, higher balance. The bond's value increases on the first day of each month, and interest is posted to your account monthly.
The formula for the future value after n years at an annual composite rate r is:
I-Bonds serve a specific role in a diversified investment portfolio. They are not designed to generate high returns like stocks, but rather to provide a safe, inflation-protected store of value. Here are some common scenarios where I-Bonds make sense:
After the first year, I-Bonds are liquid and safe, making them ideal for an emergency fund. Your principal is guaranteed, and inflation protection preserves purchasing power.
I-Bonds offer tax-free interest when used for qualified education expenses, making them a complement to 529 plans. They provide a conservative option within education savings.
As part of the fixed-income portion of a retirement portfolio, I-Bonds provide inflation protection that traditional bonds lack. Tax deferral until redemption is an added benefit.
When savings account rates are low, I-Bonds often offer higher yields, especially during inflationary periods. They can serve as a higher-yielding alternative to cash.
⚠️ Important Disclaimer: This I-Bond Calculator is for educational and informational purposes only. It provides estimates based on the inputs you provide and assumes a constant composite rate over the entire holding period (actual rates change every 6 months). Results should not be considered financial advice. I-Bond rates, terms, and purchase limits are set by the U.S. Treasury and are subject to change. Always verify current rates at TreasuryDirect.gov before making investment decisions. Consult a qualified financial advisor for personalized investment guidance.