T-bill price and yield formulas
A T-bill's price comes from its discount rate, which is quoted on a 360-day year; its investment rate (also called the bond-equivalent or coupon-equivalent yield) restates the return on the price you pay over a 365- or 366-day year, so it is always higher.[1][2]
Worked example, November 9, 2026 26-week bill: P = 100 × (1 − 0.04145 × 182/360) = 97.904472. Investment rate = (100 − 97.904472) ÷ 97.904472 × 365/182 = 4.293%, matching the 4.293% Treasury published. TreasuryDirect's own pricing page uses the same price formula.[4]
Latest Treasury bill auction rates
Treasury auctions bills every week. These are the most recent results for each regular term, from TreasuryDirect's auction results:[3]
| Bill | Auction date | Days | High discount rate | Investment rate | Price per $100 |
|---|---|---|---|---|---|
| 4-week | November 12, 2026 | 28 | 3.955% | 4.022% | $99.692389 |
| 6-week | November 9, 2026 | 42 | 3.990% | 4.064% | $99.534500 |
| 8-week | November 12, 2026 | 56 | 4.080% | 4.163% | $99.365333 |
| 13-week | November 9, 2026 | 91 | 4.060% | 4.159% | $98.973722 |
| 17-week | November 12, 2026 | 119 | 4.225% | 4.344% | $98.603403 |
| 26-week | November 9, 2026 | 182 | 4.145% | 4.293% | $97.904472 |
| 52-week | October 27, 2026 | 364 | 4.290% | 4.496% | $95.662333 |
Bill rates track the Federal Reserve's policy rate closely, because both are short-term rates.[6] Individuals usually place non-competitive bids, which accept the rate set at the auction.
Are T-bills taxable?
T-bill interest is subject to federal income tax but exempt from state and local income tax.[1][5] That exemption raises the yield a fully taxable CD or savings account must pay to match a bill. At a 22% federal rate, for the 26-week bill above:
| State and local tax rate | T-bill investment rate | Taxable APY with the same after-tax return |
|---|---|---|
| 0.0% | 4.293% | 4.293% |
| 3.0% | 4.293% | 4.464% |
| 5.0% | 4.293% | 4.587% |
| 7.0% | 4.293% | 4.716% |
| 9.3% | 4.293% | 4.874% |
| 13.3% | 4.293% | 5.175% |
The calculator uses the same comparison: taxable yield = bill yield × (1 − federal rate) ÷ (1 − federal rate − state rate). It ignores the federal deduction for state taxes, which few filers can use in full.
How to buy Treasury bills
You can buy bills directly from the Treasury at TreasuryDirect in multiples of $100, with a $100 minimum, or through a bank or broker.[1] At auction you pay the price, and at maturity you receive the face value. To spend a set amount of cash, choose "Cash I want to invest": the calculator rounds down to whole $100 of face value.
Rolling billsReinvesting a bill at maturity gives a compounded annual return slightly above the investment rate; the result shows it. Bills of different lengths can form a ladder, like a CD ladder.
T-bills vs CDs and savings
Bills are backed by the U.S. government and can be sold before maturity at the market price, though that price can be below what you paid. A CD fixes a rate for longer terms with an early-withdrawal penalty; a high-yield savings account is fully liquid at a variable rate. For inflation protection over years, compare I bonds.
Related calculators
- I bond calculatorValue of your I bond month by month with the TreasuryDirect rates
- CD calculatorValue at maturity from APY or rate, any term
- CD ladder calculatorRungs, blended APY and the ladder against a single CD
- Present value calculatorWhat a future sum or payment stream is worth today
Frequently asked questions
How do you calculate the price of a T-bill?
Price per $100 = 100 × (1 − discount rate × days ÷ 360). At 4.145% for 182 days: 97.904472.
What is the difference between the discount rate and the investment rate?
The discount rate measures the discount against face value on a 360-day year. The investment rate measures the return on the price paid on a 365- or 366-day year, so it is higher and comparable to a CD's or bond's yield.
How much does a $10,000 T-bill pay?
You receive $10,000 at maturity and pay less up front. At the latest 26-week rate the cost was $9,790.45, so the interest is $209.55.
Are T-bills taxed by the state?
No. Interest on Treasury bills is exempt from state and local income tax but subject to federal income tax.
Sources
- Treasury Bills
- 31 CFR part 356, Appendix B, Formulas and Tables (section VI, Treasury bills)
- Auctioned securities: Treasury bills, last 40 days (auction results)
- Understanding Pricing and Interest Rates
- Topic no. 403, Interest received
- Federal Reserve issues FOMC statement (target range 3-3/4 to 4 percent)