T-Bill Calculator
Price a US Treasury bill and convert its discount rate to the investment rate (yield) you actually earn
Treasury Bill
What you receive at maturity
The auction high rate
TreasuryDirect then uses a 366-day year for the investment rate
Investment rate (bond-equivalent yield)
4.139%
Pay $9,797.78 today and receive $10,000 in 182 days
Purchase price
$9,797.78
$97.977778 per $100
Interest earned
$202.22
paid as the discount at maturity
Discount rate
4.000%
on face value, 360-day year
Effective annual yield
4.182%
if rolled over at the same rate
Interest earned by term
$10,000 face value at the same 4.000% discount rate
Every T-Bill Term at This Rate
| Term | Days | Price | Interest | Investment Rate |
|---|---|---|---|---|
| 4 weeks | 28 | $9,968.89 | $31.11 | 4.068% |
| 6 weeks | 42 | $9,953.33 | $46.67 | 4.075% |
| 8 weeks | 56 | $9,937.78 | $62.22 | 4.081% |
| 13 weeks | 91 | $9,898.89 | $101.11 | 4.097% |
| 17 weeks | 119 | $9,867.78 | $132.22 | 4.110% |
| 26 weeks | 182 | $9,797.78 | $202.22 | 4.139% |
| 52 weeks | 364 | $9,595.56 | $404.44 | 4.183% |
Actual auction rates differ by term; this table holds the discount rate constant to compare terms.
How T-Bills Pay
Treasury bills are short-term US government debt sold at a discount: you pay less than face value and receive the full face value at maturity, so the difference is your interest. Auctions quote a discount rate based on face value and a 360-day year, which understates your return. The investment rate is based on the price you pay and a 365-day year, so compare that one with savings and CD yields.
The Formulas
Price per $100 = 100 × (1 − discount × days ÷ 360)
Investment rate = (100 − price) ÷ price × 365 ÷ days
Bills over 6 months use TreasuryDirect's quadratic formula
Use 366 instead of 365 when the year after purchase includes February 29.
Buying T-Bills
- •Interest is exempt from state and local income tax, but not federal tax
- •You can buy at auction through TreasuryDirect or a brokerage
- •The minimum purchase is $100, in $100 steps
- •Brokerages let you sell before maturity at the market price
- •Compare after-tax yields with CDs and savings accounts