Treasury Bill Calculator
Calculate US Treasury Bill yield, purchase price, and total earnings from the discount rate. Supports 4-week, 8-week, 13-week, 17-week, 26-week, and 52-week T-bills auctioned at TreasuryDirect.
What Is a Treasury Bill?
A US Treasury Bill (T-bill) is a short-term government debt security sold at a discount to face value and redeemed for the full face value at maturity. The difference between purchase price and face value is your interest. T-bills are auctioned in standard terms of 4, 8, 13, 17, 26, and 52 weeks at TreasuryDirect.gov with a minimum purchase of $100. They are backed by the full faith and credit of the US government and interest is exempt from state and local income tax.
Unlike bonds or CDs, T-bills do not pay periodic coupons. You pay less than face value up front, and your return is realized as a single payment at maturity. This makes T-bills attractive for parking cash that you will need at a specific future date.
How Discount Rate Becomes Real Yield
The Treasury quotes T-bills using a bank discount rate on a 360-day basis, not a true yield. Purchase price equals face value times one minus discount rate times days divided by 360. The investment yield (bond equivalent yield, or BEY) is calculated on the actual 365-day year and the price paid, not face value, so it is always higher than the discount rate. This calculator reports both so you can compare T-bills apples-to-apples with CDs and high-yield savings accounts, which quote APY on a 365-day basis.
For example, a 4.30 percent discount rate on a 13-week T-bill equals roughly a 4.41 percent investment yield. At a 22 percent federal bracket with 5 percent state tax, the after-tax yield on a T-bill beats a similarly rated CD by the state tax savings alone.
T-Bill vs High-Yield Savings vs CD
High-yield savings accounts are fully liquid and FDIC-insured but rates move with the Fed, and interest is taxed at both federal and state levels. CDs lock in a rate but charge early-withdrawal penalties and are also fully taxable. T-bills hold the state-tax exemption advantage and are easy to ladder: buy a new 13-week T-bill every month and you will have one maturing every 4 weeks for steady cash flow. During periods of inverted yield curves, short T-bills can yield more than 2-year Treasuries.
Common use cases: emergency fund above the FDIC limit, cash earmarked for a home down payment in the next 12 months, or a short-term parking spot for a tax refund or year-end bonus. Last updated April 2026 based on current US Treasury auction conventions.