Treasury Bill Calculator
This Treasury bill calculator shows what you pay for a T-bill, the interest you earn at maturity and its true yield. Enter the discount rate or price from a TreasuryDirect auction to see the investment rate, APY and what a CD or savings account would need to pay to match it after taxes.
Estimate only. Uses a 365-day year for the investment rate and APY, as TreasuryDirect does in most years. The CD comparison assumes CD interest is taxed by your state and T-bill interest is not. Ignores fees and any state tax deduction.
T-bill interest by term
This table updates with your numbers. It shows what your face value would cost and earn at each regular T-bill term if every term had the same discount rate. In real auctions, each term has its own rate.
| Term | Days | You pay | Interest | Investment rate |
|---|---|---|---|---|
| 4 weeks | 28 | $9,968.03 | $31.97 | 4.180% |
| 6 weeks | 42 | $9,952.05 | $47.95 | 4.187% |
| 8 weeks | 56 | $9,936.07 | $63.93 | 4.194% |
| 13 weeks | 91 | $9,896.11 | $103.89 | 4.211% |
| 17 weeks | 119 | $9,864.14 | $135.86 | 4.224% |
| 26 weeks | 182 | $9,792.22 | $207.78 | 4.256% |
| 52 weeks | 364 | $9,584.43 | $415.57 | 4.302% |
How the Treasury bill calculator works
A Treasury bill does not pay interest along the way. You buy it for less than its face value, and the government pays you the full face value when it matures. The difference is your interest.
For the 52-week bill, which is longer than half a year, the investment rate uses the Treasury’s formula for bills that span more than one half-year period. The calculator handles that for you.
Example: In the 13-week auction on September 28, 2026, the high (discount) rate was 4.110%. A $10,000 bill cost $9,896.11 and pays $10,000 after 91 days, so the interest is $103.89. That is an investment rate of 4.211% and an APY of 4.28%.
Discount rate vs. investment rate vs. APY
| Rate | What it means | 13-week example |
|---|---|---|
| Discount rate | Discount as a % of face value, on a 360-day year. Used to set the auction price. | 4.110% |
| Investment rate | Your return on the price paid, on a 365-day year. Also called bond equivalent yield. | 4.211% |
| APY | Return if you rolled into new bills at the same rate for a full year. | 4.28% |
The discount rate always looks lower than what you really earn. To compare a T-bill with a high-yield savings account or a CD, which quote APY, use the APY or the investment rate.
Treasury bill terms and auctions
The Treasury sells bills with terms of 4, 6, 8, 13, 17, 26 and 52 weeks. Most terms are auctioned every week, and the 52-week bill every four weeks. You can buy at TreasuryDirect with no fees, starting at $100, or through a brokerage account. Many investors build a T-bill ladder, with bills maturing every few weeks, so cash keeps coming due while the rest keeps earning.
Short-term bill rates follow the Federal Reserve’s policy rate more than long-term bond yields do. In late September 2026, the 13-week bill paid an investment rate of about 4.21%, while the 10-year Treasury yield climbed above 5.3% on October 1, its highest level since 2002. Our bond yield calculator shows how longer bonds react when yields move.
How T-bill interest is taxed
- Federal income tax: yes, at your ordinary income tax rate. At 22%, $103.89 of interest leaves about $81.04.
- State and local income tax: no. Interest on U.S. Treasury securities is exempt, which is a real advantage in high-tax states.
- When it is taxed: generally in the year the bill matures, reported on Form 1099-INT.
Because CD and savings interest is taxed by your state, a T-bill can beat a CD with a slightly higher stated rate. The calculator’s “CD or savings APY to match” line shows the rate a taxable account would need to pay to leave you with the same after-tax return. To estimate your federal bracket, try our income tax calculator.
T-bills vs. CDs vs. high-yield savings
| Treasury bill | CD | High-yield savings | |
|---|---|---|---|
| Backed by | U.S. government | FDIC or NCUA insurance up to $250,000 | FDIC or NCUA insurance up to $250,000 |
| State income tax | Exempt | Taxed | Taxed |
| Rate | Fixed until maturity | Fixed until maturity | Can change any time |
| Getting money early | Sell at market price (brokerage) | Early withdrawal penalty | Withdraw any time |
| Terms | 4 to 52 weeks | Usually 3 months to 5 years | No term |
Compare the same deposit in our CD calculator, and keep your emergency fund somewhere you can reach on short notice.
Frequently asked questions
How much interest does a $10,000 T-bill earn?
At the 4.110% discount rate from the September 28, 2026 13-week auction, a $10,000 13-week T-bill costs about $9,896.11 and pays back $10,000 at maturity, so you earn about $103.89 in 91 days. That works out to an investment rate of about 4.21%.
What is the difference between the discount rate and the investment rate?
The discount rate is based on the face value and a 360-day year, so it understates your real return. The investment rate, also called the bond equivalent yield or coupon equivalent, is based on the price you actually pay and a 365-day year. Use the investment rate or APY to compare a T-bill with a CD or savings account.
Are Treasury bills taxed?
T-bill interest is subject to federal income tax but is exempt from state and local income tax. The interest is the difference between what you paid and the face value, and it is generally reported in the year the bill matures on Form 1099-INT.
Can I sell a T-bill before it matures?
Yes, if you hold it at a brokerage you can sell it on the secondary market before maturity, but the price depends on current rates and you could get less than you paid plus interest. Bills held at TreasuryDirect must be transferred to a broker before they can be sold. If you hold to maturity, you always receive the full face value.
Are T-bills safe?
Treasury bills are backed by the full faith and credit of the U.S. government and are considered among the safest investments for U.S. dollars. Their main risk is that rates can change, so the rate you get when you roll into a new bill may be higher or lower.
How do I buy a Treasury bill?
You can buy T-bills directly from the government at TreasuryDirect.gov in amounts starting at $100, in $100 steps, or through most brokerage accounts. Bills are sold at auction, and you can choose to reinvest automatically when one matures.
Sources and how we calculated
Prices and yields follow the formulas the Treasury uses for marketable bills, as described at TreasuryDirect. The September 28, 2026 13-week auction rates (4.110% high rate, 4.211% investment rate) are from published auction results; you can confirm any auction in the Treasury’s official results. The October 1, 2026 10-year yield is from TheStreet’s market report.
This calculator is for educational purposes only and is not investment or tax advice. Rates change at every auction. We do not recommend buying or selling any security. Check current auction results and your own tax situation before investing.