A HYSA rate comparison helps you find the best after-tax yield across three low-risk savings vehicles: high-yield savings accounts, money market accounts, and Treasury bills. The key insight is that T-Bill interest is exempt from state and local taxes — making T-Bills often more attractive than their headline rate suggests, especially for residents of high-tax states.
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1-Year After-Tax Earnings Comparison
This tool is for informational and educational purposes only. Not financial advice. Consult a qualified advisor before making investment decisions. Rates change frequently.
How to Use the HYSA Rate Comparison Calculator
With savings rates finally competitive after years of near-zero yields, choosing between a high-yield savings account, money market account, and Treasury bills can meaningfully impact your annual earnings. This HYSA rate comparison calculator factors in your specific tax situation to show the true after-tax yield for each option.
Step 1: Enter Your Deposit Amount
Input the amount you plan to save or already have parked in a savings vehicle. The calculator will show dollar-denominated earnings for each option alongside percentage yields, making it easy to understand the real-dollar difference.
Step 2: Set Your Tax Brackets
Enter your federal marginal tax bracket and your state income tax rate. These are critical inputs because HYSA and money market interest is subject to both federal and state taxes, while T-Bill interest is state-tax-exempt. For residents of California (13.3% top rate), New York (10.9%), or New Jersey (10.75%), this distinction can swing the comparison significantly.
Step 3: Enter Current Rates
Input the current APY from your HYSA or money market account (check your bank's current rate, as these change frequently), and the current annualized yield on the T-Bill maturity you're considering. T-Bill rates for 4-week, 13-week, and 26-week bills are published weekly by the U.S. Treasury after each auction.
Step 4: Interpret the Results
The calculator shows after-tax yield and dollar earnings for each account type. The highlighted winner reflects the option with the highest after-tax return given your specific tax situation. If the T-Bill rate looks lower on paper but still wins after accounting for state tax exemption, that's the power of this comparison tool.
Key Considerations Beyond Yield
Yield isn't the only factor. HYSAs and money market accounts offer instant liquidity — you can withdraw any day. T-Bills have a fixed maturity (4 to 52 weeks) and while they can be sold before maturity, this adds complexity. HYSAs at FDIC-insured banks also offer deposit insurance up to $250,000, while T-Bills are backed by the U.S. government. For most savers with under $250,000, safety is effectively equal; the main trade-off is liquidity vs. yield.
FAQ
Is this HYSA comparison calculator free?
Yes, completely free with no signup required. All calculations run in your browser — your financial data is never sent to any server.
Is my financial data private?
Absolutely. Everything runs entirely in your browser using client-side JavaScript. No data is transmitted or stored anywhere.
Why does my tax bracket matter for HYSA vs T-Bill comparison?
HYSA and money market interest is fully taxable at both federal and state levels. T-Bill interest is federally taxable but exempt from state and local taxes. For residents of high-tax states like California or New York, this state tax exemption can make T-Bills meaningfully more attractive than their headline rate suggests.
What is the difference between HYSA and money market accounts?
Both are FDIC-insured savings vehicles, but money market accounts may offer check-writing and debit card access. HYSAs are typically online-only with higher APYs. Money market mutual funds (not bank accounts) are not FDIC-insured and invest in short-term debt. This calculator focuses on bank-based accounts and Treasury bills.
Are T-Bills safer than a high-yield savings account?
T-Bills are backed by the full faith and credit of the U.S. government, making them the benchmark risk-free asset. HYSAs at FDIC-insured banks are insured up to $250,000 per depositor per institution. For amounts under $250,000, both carry effectively zero credit risk.
How often do HYSA and T-Bill rates change?
HYSA and money market rates can change any time at the bank's discretion and typically follow Federal Reserve rate decisions. T-Bill rates are set at weekly auctions and reflect current market conditions. When rates are falling, T-Bills let you lock in today's rate for the full term, while HYSAs will follow rates down.
What is the effective after-tax rate shown in the results?
The effective after-tax rate is the yield you actually keep after paying federal income tax. For T-Bills, this assumes no state tax applies (since T-Bill income is state-tax-exempt). For HYSA and money market, it assumes the full marginal tax rate applies. This makes the comparison apples-to-apples.