CD vs HYSA vs T-Bill After-Tax Calculator
A 4.5% CD and a 4.5% T-Bill are not equal — interest from the first is taxed by federal and state governments, while T-bill interest is state-exempt. This calculator converts all three to their after-tax yields so you compare apples to apples.
How to use this calculator
- Enter advertised APY (same for all three).
- Enter federal marginal tax rate.
- Enter state income tax rate.
- Your results appear instantly below and update as you change the numbers.
How this calculator works
CD and HYSA interest is fully taxable: after-tax yield = APY × (1 − federal − state). Treasury interest is exempt from state tax: after-tax yield = APY × (1 − federal). Example: 4.5% at 22% federal + 5% state → 3.29% for the CD/HYSA but 3.51% for the T-Bill — the T-Bill wins at equal APY.
Frequently asked questions
Does the T-Bill still win after the federal tax?
Only the state exemption is unique to Treasuries — federal tax applies to all three. In a no-income-tax state (Texas, Florida, etc.) the comparison is purely federal, and T-Bills lose their edge at equal APY.
What about liquidity?
HYSAs win on liquidity — money moves the same day. CDs lock your money (with an early-withdrawal penalty), and T-Bills are liquid on the secondary market but a hassle for very short horizons.
Is the FDIC/backing different?
CDs and HYSAs are FDIC-insured up to $250,000 per bank; T-Bills are backed by the full faith and credit of the U.S. government. Both are effectively risk-free for practical purposes.
Disclaimer: Results are estimates for general information only and do not constitute financial, tax, or legal advice. Figures reflect 2026 rules and may change. Always confirm current limits and consult a qualified professional before making decisions. Official figures: IRS.gov · 2026 limits per IRS tax inflation adjustments.