Savings & Investing

I Bond vs HYSA Calculator

Compare I Bond returns against high-yield savings accounts including penalty scenarios and tax treatment.

Decision Summary

I Bond vs HYSA difference (after tax)

$394.06

I Bond provides better after-tax return over the holding period.

Scenario Comparison

The main answer and the most important supporting outputs in one glance.

I Bond vs HYSA difference (after tax)

$394.06

I Bond after tax

$12,225.09

HYSA after tax

$11,831.03

Early withdrawal penalty

$0.00

Key Metrics

I Bond after tax

$12,225.09

HYSA after tax

$11,831.03

Early withdrawal penalty

$0.00

Break-even holding period

1 years

How to use it

Enter the amount to invest, current I Bond composite rate, current HYSA APY, your marginal tax rate, state tax rate, and investment horizon. I Bonds are state-tax-free and federal-tax-deferred, which changes the comparison versus a fully taxable HYSA.
Read after-tax return for each option over your time horizon and the break-even rate where they are equivalent. When inflation is high, the I Bond variable rate can significantly exceed HYSA yields, but the rate resets every 6 months.
I Bonds have a 1-year lockup and a 3-month interest penalty if redeemed before 5 years, so they lose on liquidity. If you might need the money within 12 months, the HYSA wins regardless of rate because you cannot access the I Bond at all.
Use I Bonds for money you will not need for at least 1-3 years and keep your emergency fund in the HYSA. The $10,000 annual purchase limit per person caps the strategy naturally. Compare both against the CD ladder calculator for intermediate horizons.
Re-run when I Bond rates reset in May and November, when HYSA rates change, or when your tax bracket shifts. Track the composite I Bond rate, HYSA APY, and the after-tax spread.

AI Integrations

Contract, discovery endpoints, and developer notes for agent use.

Always available for agents

Tool contract JSON

https://aifinhub.io/contracts/i-bond-vs-hysa-calculator.json

Stable input and output contract for this exact tool.

Human review

People can use the browser page to sense-check outputs and charts, but agents should still execute against the contract and discovery endpoints.

/agent-tools.json - machine-readable tool index.
/llms.txt - human-readable model discovery guide.
/.well-known/webmcp.json - WebMCP capabilities manifest.
/.well-known/ai-plugin.json - plugin-style discovery manifest.

{
  "tool": "i_bond_vs_hysa",
  "investment_amount": 10000,
  "i_bond_composite_rate_percent": 5.27,
  "hysa_apy_percent": 4.5,
  "years": 5,
  "tax_rate_percent": 22
}

Open tool contract JSON Open AI integrations guide

Expand developer notes

Agent playbook

Resolve I Bond vs HYSA Calculator from /agent-tools.json and open its contract before execution.
Validate inputs against the contract schema instead of scraping labels from the page UI.
Open the browser page only when a person wants to review charts, assumptions, or related tools.

Agent FAQ

Should ChatGPT, Claude, or another agent click through the UI?

No. Start with /agent-tools.json, then follow the tool's contract URL. The page UI is for human review, not parameter discovery.

When do tools show Quick and Advanced?

Every tool opens in Quick Start first. Advanced Controls keeps the same scenario, reveals more assumptions or diagnostics, and every tool keeps AI integrations inline below the instructions.

When should an agent still open the browser page?

Open it when a human wants to sense-check the output, review the chart, or keep exploring related tools after the calculation finishes.

Questions people usually ask

What does this compare?

It models the after-tax returns of I Bonds (inflation-adjusted, tax-deferred, state-tax-exempt) versus a High-Yield Savings Account (taxable interest, fully liquid). The right choice depends on your time horizon, tax bracket, and liquidity needs.

When are I Bonds better than a HYSA?

I Bonds win when inflation is high (their rate adjusts every 6 months), your tax bracket is high (interest is tax-deferred and state-tax-free), and you can lock up money for at least 1 year (5 years to avoid the 3-month interest penalty). In low-inflation environments, HYSAs may offer comparable or better yields with full liquidity.

What are the limitations of I Bonds?

You can only buy $10,000/person per year electronically (plus $5,000 via tax refund). They cannot be redeemed in the first 12 months, and redeeming before 5 years forfeits the last 3 months of interest. These liquidity constraints make them unsuitable for emergency funds.

When should I use this vs a general savings comparison tool?

Use this for the specific I Bond vs HYSA decision. General savings tools do not model I Bond mechanics like inflation adjustments, tax deferral, state tax exemption, or the early redemption penalty.

Is my data stored?

No. All calculations happen in your browser. Nothing is stored or transmitted.