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T-bill vs. savings calculator
Bills skip state income tax. Here is what that is worth where you live.
| One year | T-bill | Savings / CD |
|---|---|---|
| Interest before tax | $1,046 | $1,000 |
| After federal and state tax | $816 | $730 |
At these inputs the T-bill leaves $86 more a year after tax. A savings account would need about 4.47% APY to match it.
Prefilled with the latest 13-week bill auction (4.185% investment rate, Tue, Oct 13, 2026) and a hypothetical 4.00% APY, not any bank's offer. Enter your own bank's annual percentage yield from its rate page; minimum balances and fees can reduce what you earn. The FDIC national average savings APY is 0.38%, accurate as of October 2026, which at these inputs leaves $69 after tax against the bill's $816.
Data may be stale.The latest observation is 11 days old, longer than this series' usual publishing cycle.
Source: U.S. Treasury, Fiscal Data: Treasury Securities Auctions Data. Latest observation: auction of Tue, Oct 13, 2026. Pulled Oct 26, 2026, 10:30 AM ET. Savings average: FDIC, National Rates and Rate Caps (monthly), via FRED.
Break-even APY by state tax rate
The savings APY that matches a 4.185% bill after tax, at a 22% federal rate:
| State + local rate | Break-even APY |
|---|---|
| 0% | 4.18% |
| 3% | 4.35% |
| 5% | 4.47% |
| 7% | 4.60% |
| 9.3% | 4.75% |
| 10.9% | 4.86% |
How it works
T-bill interest is taxed federally and exempt from state and local income tax; savings and CD interest is taxed at every level. The calculator applies your federal rate to both and your state rate to the savings side only. It assumes state tax is not deducted on your federal return and ignores compounding, so it is a one-year snapshot at today's rates. Rules: TreasuryDirect: Treasury bills.
See today's bank rates next to bill yields on savings and CD rates today, and the latest auction results on Treasury bills.
Common questions
Why do T-bills come out ahead after tax?
Treasury bill interest is exempt from state and local income tax. Savings and CD interest is not. The higher your state tax rate, the higher a savings APY has to be to match a bill.
What is the break-even savings rate?
The APY at which a fully taxable savings account leaves the same after-tax interest as a T-bill: bill rate x (1 - federal rate) / (1 - federal rate - state rate).
Does this include compounding?
No. It compares one year of simple interest at today's rates. In practice bills are rolled at future auction rates and savings APYs change, so treat the result as a snapshot.