I-Bond Calculator

Calculate Series I savings bond value from fixed rate, inflation rate, holding period, and early redemption penalty.

Financial Disclaimer

This calculator is for educational purposes only and does not constitute financial advice. Results are estimates based on the inputs provided. Consult a qualified financial advisor before making investment or financial planning decisions.

Inputs

Purchase amount ($)

Fixed rate (%)

Inflation rate (%)

Holding period (years)

Federal tax bracket (%)

Tab to move between fields

Results

Redemption value ($)

$12,070.96

≈ 8 months of rent

Composite rate (%)3.8%

Total interest earned ($)$2,070.96

Early penalty ($)$0.00

After-tax value ($)$11,615.35

Effective annual yield (%)3.84%

How to Use This Calculator

Enter your I-Bond purchase amount (up to $10,000 per person per year from TreasuryDirect).
Input the fixed rate and current inflation rate — check TreasuryDirect.gov for current rates.
Set your expected holding period in years and your federal income tax bracket.
Review Composite Rate, Redemption Value, and Total Interest to see your projected return.
Check Early Redemption Penalty and Effective Annual Yield if you may need to cash out before 5 years.

How the result changes with Purchase amount ($)

Purchase amount ($)	Redemption value ($)
1,023	$1,234.86
3,516	$4,244.15
6,509	$7,856.99
9,003	$10,867.49

What each input means

Purchase amount ($): I-Bond purchase amount ($25 min, $10,000/year max).
Fixed rate (%): Fixed rate component (set at purchase, lasts 30 years).
Inflation rate (%): Annual CPI-U inflation rate (adjusts every 6 months).
Holding period (years): Years you plan to hold (min 1 year, penalty if < 5).
Federal tax bracket (%): Your federal income tax bracket.

What each result means

Composite rate (%): Combined fixed + inflation rate.
Redemption value ($): Value at redemption after any penalty.
Total interest earned ($): Interest earned over holding period.
Early penalty ($): 3-month interest penalty if held < 5 years.
After-tax value ($): Value after federal income tax on interest.
Effective annual yield (%): Actual annualized return after penalties.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Purchase amount ($) = 10000, Fixed rate (%) = 1.3, Inflation rate (%) = 2.5, Holding period (years) = 5 = 5 input(s) provided
Calculate Redemption value
Redemption value
12070.96 = $12,070.96
Calculate Composite rate
3.8 = 3.8%
Calculate Total interest earned
Total interest earned
2070.96 = $2,070.96