Treasury Bill Calculator

At the 26-week bill auction of Oct 13, 2026, a 4.20% discount rate prices a $10,000 bill at $9,787.67, pays $212.33 of interest at maturity, and equals an investment rate of 4.351%.

Your bill

Enter the discount rate from the auction or your broker. Nothing you type leaves your browser.

Face value ($)What the bill pays at maturity. Minimum $100, in steps of $100.Discount rate (%)Latest 26-week auction: 4.200%

Term (weeks, 4 to 52)

Issue date (optional)Decides whether the investment-rate year has 365 or 366 days.Maturity date (optional)With an issue date, sets the exact days. A bill maturing on a holiday runs one day longer than weeks x 7.

Result

You pay: $9,787.67; 97.876667 per $100 of face value
Interest at maturity: $212.33; Paid with the $10,000.00 face value after 182 days
Investment rate (coupon-equivalent yield): 4.351%; On a 365-day year
Discount rate: 4.200%; On a 360-day year, measured on face value

Latest Treasury bill auction results

Newest published result per term from Treasury Fiscal Data, read Oct 27, 2026.

Term	Auction	Discount rate	Investment rate	Price per $100
4 weeks	Oct 15, 2026	4.000%	4.068%	99.688889
6 weeks	Oct 13, 2026	3.980%	4.055%	99.524611
8 weeks	Oct 15, 2026	4.050%	4.132%	99.370000
13 weeks	Oct 13, 2026	4.085%	4.185%	98.967403
17 weeks	Oct 14, 2026	4.195%	4.313%	98.613319
26 weeks	Oct 13, 2026	4.200%	4.351%	97.876667
52 weeks	Sep 29, 2026	4.400%	4.616%	95.551111

How it is calculated

A Treasury bill pays no coupons. You buy it below face value and are paid the face value at maturity, so the interest is the difference. The price comes from the discount rate, which Treasury quotes on a 360-day year. Days to maturity are counted from the issue date to the maturity date: normally the term in weeks times 7, one more when maturity falls on a holiday.

Price per $100 = 100 x (1 - discount rate x days / 360), rounded to six decimals.
Purchase price = face value / 100 x price per $100. Interest = face value - purchase price.
Investment rate for bills of up to half a year = (100 - price) / price x (year days / days).
For longer bills (the 52-week bill) the investment rate solves a quadratic equation, because the formula allows for interest on interest in the second half of the year.

Worked example: the Oct 13, 2026 26-week auction gave a 4.20% discount rate. Over 182 days that is a price of 97.876667 per $100, so $9,787.67 for a $10,000 bill. Treasury published 4.351% as the investment rate for that auction.

Sources

TreasuryDirect, Understanding Pricing: “Price = Face value (1 – (discount rate x time)/360)” Read Oct 27, 2026.
31 CFR Part 356, Appendix B, Section VI.A (Cornell LII): “Purchase prices per $100 are rounded to six decimal places, using normal rounding procedures.” Read Oct 27, 2026.
31 CFR Part 356, Appendix B, Section VI.D (Cornell LII): “For bills of not more than one half-year to maturity: i = (100 - P) / P x y / r” Read Oct 27, 2026.
TreasuryDirect, Treasury Bills: “For bills, "interest" is the difference between what you paid and the face value you get when the bill matures.” Read Oct 27, 2026.
TreasuryDirect, Treasury Bills (terms and purchase limits): “4, 6, 8, 13, 17, 26, and 52 weeks. Minimum purchase $100, in increments of $100.” Read Oct 27, 2026.
U.S. Treasury, Fiscal Data: Treasury Securities Auctions Data: “Fields used: high_discnt_rate, high_investment_rate, high_price, issue_date, maturity_date.” Read Oct 27, 2026.

The boundary between the short and the quadratic formula follows the regulation's wording, “not more than one half-year”. We checked the formulas against the published Treasury examples and the auction results above.

Treasury bill questions

How much does a $10,000 26-week Treasury bill cost?

At a 4.20% discount rate (the Oct 13, 2026 auction), the price is 97.876667 per $100 of face value, so $9,787.67 for $10,000. At maturity, 182 days later, you are paid the full $10,000.

How much interest does a Treasury bill pay?

Interest is the face value minus the price you paid, and it is paid at maturity, not in coupons. In the example above it is $212.33.

What is the difference between the discount rate and the investment rate?

The discount rate is quoted on the face value over a 360-day year. The investment rate (coupon-equivalent yield) is measured on the price you pay over a 365-day year, so it is higher. In the example, 4.20% discount equals 4.351% investment rate.

What terms can I buy, and how much is the minimum?

Bills mature in 4, 6, 8, 13, 17, 26 and 52 weeks. The minimum purchase is $100, in increments of $100. This calculator accepts any whole number of weeks from 4 to 52 so you can price a bill you bought on the secondary market.

Why does the calculator need an issue date?

Only to pick the year length in the investment-rate formula. It is 366 days if the year after the issue date contains February 29 and 365 otherwise. Leave it blank for 365.

This calculator is an educational tool, not personal investment or tax advice. Results follow the published Treasury formulas for the rate you enter; the price you actually pay is set at auction or by the market, and past auction rates do not predict future ones.