T-Bill Yield Calculator
Convert between a T-bill’s price per $100, its discount rate and its investment rate (the yield comparable to other investments).
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Investment rate
- Discount rate
- Price per $100
- You pay
- Interest earned
- Annualized (compounded)
- Work
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T-Bill Yield Formulas
T-bills are sold at a discount and pay face value at maturity. Treasury reports two rates:
Discount rate = (100 − P) ÷ 100 × 360 ÷ days
Investment rate (≤ 182 days) = (100 − P) ÷ P × 365 ÷ days
For bills longer than a half year, TreasuryDirect solves a quadratic that accounts for semiannual compounding. The investment rate is the one to compare with CDs, savings accounts and notes.
Worked Example
Tips
Treasury uses 366 days when the year following the issue date contains February 29; this page uses 365, which can shift the last digit. T-bill interest is exempt from state and local income tax; see the CD vs Treasury calculator.