T-Bill Calculator
Calculate discount yield, investment yield (BEY), and profit for any Treasury bill — or find the purchase price from a known discount rate.
Inputs
Formulas Used
T-bills are sold at a discount. The difference between the purchase price and face value is your return. Two yield conventions are used; both are shown.
- FV = Face value
- P = Purchase price
- t = Days to maturity
- 360-day year (bank discount convention)
- FV = Face value
- P = Purchase price
- t = Days to maturity
- 365-day year; comparable to coupon-bond yields and CD APY
Price from rate: P = FV × (1 − d × t/360) — the inverse of discount yield, used in Rate → Price mode.
Yield Across All Standard Terms
Shows how yield and price differ across every standard T-bill term at the same discount rate. Enter a rate in Rate → Price mode to populate this table.
| Term | Days | Price ($10k par) | Discount Yield | Inv. Yield (BEY) | Profit |
|---|
Current auction rates: TreasuryDirect.gov. Rates change at each auction. Do not rely on a cached rate; always verify before investing.
Frequently Asked Questions
Discount yield uses face value as the denominator and a 360-day year — it is the rate quoted at Treasury auctions. Investment yield (BEY, or bond-equivalent yield) uses the purchase price as the denominator and a 365-day year, making it directly comparable to CD APY or coupon-bond yields. BEY is almost always slightly higher than the discount rate for the same T-bill.
Current auction results are published at TreasuryDirect.gov under "Recent Auction Results." Rates change at each weekly auction. This calculator does not hardcode rates — enter the rate from the latest auction for an accurate result.
A Treasury bill (T-bill) is a short-term U.S. government debt obligation with a maturity of one year or less. Unlike bonds, T-bills do not pay periodic interest (coupons). Instead, they are issued at a discount and redeemed at face value — the difference is your return. They are backed by the full faith and credit of the U.S. government.
T-bill interest is subject to federal income tax but exempt from state and local income tax. Consult a tax professional for your specific situation. This calculator does not compute after-tax returns.
Yes. You can purchase T-bills directly at TreasuryDirect.gov with no commission. They are also available through most brokerage accounts, where they trade in the secondary market.