Introduction
A Treasury bill (T-Bill) is a short-term loan you make to the government. You buy it for less than it is worth, and at the end of the term you get the full amount back. That gap is your profit. T-Bills do not pay interest along the way, so the discount is the interest.
This Treasury Bill Calculator does the math for you. Enter your value date, maturity date, face value, and the discount rate. The calculator shows the price you pay today, the interest you earn, and the total you get at maturity.
You can also work backward. If you already know the price you paid, switch modes and the tool finds the discount rate for you.
The results include four key numbers:
- Purchase price — what you pay today.
- Interest earned — face value minus the price.
- Discount rate — the quoted rate, based on face value and a 360-day year.
- Investment yield (BEY) — your true return, based on what you really paid and a 365-day year.
You also get an effective annual yield, a step-by-step solution, charts, and a table that compares the standard 4-week, 13-week, 26-week, and 52-week terms. Use it to compare T-Bill options and see exactly how much you will make before you invest. For longer-dated government debt, switch to the Treasury Bond Calculator or the Savings Bond Calculator.
How to use our Treasury Bill Calculator
Enter your dates, your face value, and either a discount rate or the price you paid. The calculator shows your purchase price, interest earned, days to maturity, discount rate, investment yield (BEY), effective annual yield, and a step-by-step solution.
Value Date: Pick the day your money settles and the T-Bill starts. This can be later than the day you buy it.
Maturity Date: Pick the day the bill pays out. It must come after the value date.
Days to Maturity: This box fills in on its own. It counts the calendar days between your two dates. You can double-check any span with the Date Duration Calculator or the Days Calculator.
Quick-select standard tenor: Tap 4, 13, 26, or 52 weeks to set the maturity date fast from your value date.
Face Value: Type the amount you get back at maturity. The smallest amount is $1,000, and the tool shows how many $1,000 T-Bill units that equals.
Calculation Mode: Choose "Calculate Purchase Price" if you know the rate. Choose "Calculate Discount Rate" if you know the price you paid.
Price Paid: Only shows in the second mode. Type what you pay today. It must be less than the face value.
Rate Source: Choose a preset published rate or pick "Use custom rate" to type your own.
Published Discount Rate: Pick a rate from the list, like 5.00%. Choose "Other" to switch to the custom box.
Custom Rate: Type the yearly discount rate as a percent, such as 5.25. If you only know a dollar return and want to solve for the rate instead, the interest rate calculator can help.
Result Decimal Precision: Choose 2, 3, 4, or 5 decimals for how exact your results look.
Calculate and Reset: Click Calculate to see your results, charts, and math steps. Click Reset to start over with the default values.
What Is a Treasury Bill?
A Treasury bill, or T-Bill, is a short-term loan you make to the government. You buy the bill for less than it is worth, and the government pays you the full value when the bill matures. That gap is your profit. T-Bills do not pay interest every month or year like a bond does. All of your return comes from the discount you get at the start. Coupon-paying bonds work differently — see the Bond Calculator and Bond Yield Calculator for that side of the market.
How T-Bill Pricing Works
Every T-Bill has a face value, which is the amount you get back at maturity. You pay a lower price today, called the purchase price. The size of that discount depends on two things: the discount rate and the number of days until maturity. A higher rate or a longer term means a bigger discount and a lower price.
Here is the basic math:
- Purchase Price = Face Value × (1 − (Rate × Days ÷ 360))
- Interest Earned = Face Value − Purchase Price
Example: a $10,000 bill at a 5% discount rate for 91 days costs about $9,873.61. You earn $126.39 when it matures. This is a discounting exercise at heart, so the Present Value Calculator and Future Value Calculator handle the same idea for other cash flows.
Common T-Bill Terms
Treasury bills are sold in standard lengths, called tenors. The most common ones are:
- 4 weeks (28 days)
- 13 weeks (91 days)
- 26 weeks (182 days)
- 52 weeks (364 days)
Bills are usually sold in units of $1,000, so a $10,000 face value equals 10 units.
Discount Rate vs. Investment Yield
These two numbers sound alike but are not the same, and mixing them up is a common mistake.
The discount rate is the quoted rate. It measures your profit against the face value and uses a 360-day year. The investment yield, also called the bond equivalent yield or BEY, measures your profit against the money you actually paid and uses a 365-day year. Because you pay less than face value, the investment yield is always higher than the discount rate. The investment yield is the better number to use when you compare a T-Bill to a savings account or a CD — run the alternatives through the CD Calculator, the HYSA Calculator, or the Money Market Calculator.
The effective annual yield goes one step further. It shows what you would earn in a year if you kept buying new bills at the same rate and let your profit compound. The APY Calculator and the Compound Interest Calculator apply the same compounding logic to deposits and longer holdings, and the Effective Interest Rate Calculator converts between quoted and effective rates.
Value Date and Maturity Date
The value date is the day your money settles and the investment starts. This can be a day or two after you buy. The maturity date is the day you get the full face value back. The days between these two dates drive the whole calculation, so getting them right matters. If you are counting forward from a settlement date, the Days From Date Calculator and the Business Days Calculator are handy companions.
Why People Buy T-Bills
T-Bills are backed by the government, so they carry very low credit risk. They are short, so your money is not tied up long. You know exactly how much you will get and when. In many places, the interest is free from state and local income tax, though federal tax still applies. Check the rules where you live, and estimate the federal bite with the Income Tax Calculator or the Marginal Tax Rate Calculator.
The trade-off is that returns are modest. T-Bills are a place to park cash safely, not a way to grow wealth fast. Many people use them for an emergency fund or short-term savings goals, while longer-horizon money goes into the Investment Calculator or an Index Fund Calculator plan. If you sell before maturity, the price you get depends on market rates at that time, and you could get back less than you expected. To measure a completed T-Bill against other holdings, the ROI Calculator and CAGR Calculator put everything on the same footing.