Savings Bond Calculator
Enter the purchase amount, the interest rate and how long you hold the bond to see its value, interest and after-tax result.
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I bond composite rate or EE fixed rate, from TreasuryDirect. Assumed constant.
1 to 30 years. Before 5 years the last 3 months of interest are lost.
Due when you cash the bond. No state tax.
- Interest earned
- $2,189.94
- Federal tax on interest
- $481.79
- Value after tax
- $11,708.16
- Interest forfeited (under 5 years)
- $0.00
How this was calculated
- Semiannual rate = 4% ÷ 2 = 2%, added 10 time(s) in 60 months.
- Value = 10000 × (1 + 0.02)^10 = 12189.94.
The I bond rate changes every six months; this uses one constant rate. Educational estimate, not tax or investment advice.
How a savings bond grows
This savings bond calculator values a US Series I or Series EE bond. Interest accrues every month and is added to the bond twice a year, so the value compounds semiannually at half the annual rate each time. A $10,000 bond at 4% for five years is worth 10,000 × 1.0210 = $12,189.94, which is $2,189.94 of interest. The calculator shows the same arithmetic in its steps.
Series I and Series EE
An I bond pays a composite rate made of a fixed rate that stays the same for the life of the bond and an inflation rate that TreasuryDirect resets every May and November. A Series EE bond pays a fixed rate set when you buy it and is guaranteed to double in value after 20 years: a $1,000 EE bond at 1% would be worth $1,220 after 20 years on interest alone, so the Treasury tops it up to $2,000. Because the I bond rate changes, enter the current composite rate as a constant to get an estimate, and rerun it when the rate resets.
Holding rules and the penalty
You cannot cash a bond in its first 12 months. If you redeem before five years, you lose the last three months of interest, which is why the result for a bond cashed at two years is lower than a plain compound-interest figure. After five years there is no penalty. A bond keeps earning for up to 30 years.
Tax on savings bond interest
The interest is subject to federal income tax but exempt from state and local income tax. You can pay the tax each year or defer it until you cash the bond or it matures, and the calculator deducts the tax at the rate you enter. Interest may be excluded from tax when it pays for qualified higher education expenses, subject to income limits (IRS Form 8815). Sources: TreasuryDirect (rules for Series I and EE bonds) and IRS Publication 550. For other savings options compare a CD, or model growth with the compound interest calculator.
Frequently asked questions
How is a savings bond's value calculated?
Interest accrues monthly and is added every six months, so the value compounds semiannually at half the annual rate. $10,000 at 4% for 5 years is 10,000 × 1.02^10 = $12,189.94.
What is the penalty for cashing a savings bond early?
You cannot cash a bond in the first 12 months. If you redeem it before 5 years, you lose the last 3 months of interest. After 5 years there is no penalty.
Do Series EE bonds double in 20 years?
Yes. Series EE bonds are guaranteed to be worth at least double their purchase price after 20 years, even if the fixed rate would give less.
Is savings bond interest taxable?
Interest is subject to federal income tax, paid yearly or when you cash the bond, but it is exempt from state and local income tax. It may be tax-free when used for qualified education costs.
Which interest rate should I enter for an I bond?
Use the current composite rate on TreasuryDirect. It resets every May and November, so the calculator assumes the rate you enter stays constant.