Treasury Bill Calculator
Created by: Emma Collins
Last updated:
Calculate Treasury bill discount yield, bond-equivalent yield, effective annual yield, and after-tax advantage versus taxable alternatives with federal and state tax context.
Treasury Bill Calculator
FinanceEstimate Treasury bill discount yield, bond-equivalent yield, and effective annual yield with after-tax comparisons against taxable alternatives.
What Is a Treasury Bill Calculator?
A Treasury bill calculator helps you evaluate short-term U.S. government securities purchased at a discount and redeemed at face value.
Instead of a coupon payment, your return is the difference between purchase price and maturity value.
This calculator focuses on three common yield views: discount yield, bond-equivalent yield, and effective annual yield.
Seeing all three together reduces confusion when comparing T-bills with CDs, money market products, or other fixed-income options.
Because T-bills are generally exempt from state and local income tax, the after-tax comparison can differ meaningfully from headline yields.
That tax context is often where T-bills gain their practical edge in taxable accounts.
How Treasury Bill Yield Analysis Works
The calculator starts from either purchase price or discount-rate assumptions and computes the dollar discount earned at maturity.
It annualizes that return using standard conventions to produce discount yield, bond-equivalent yield, and effective annual yield.
It then applies federal and state tax assumptions to compare after-tax outcomes against a taxable alternative yield.
The result is an apples-to-apples view of where T-bills stand once tax drag is acknowledged.
Core Treasury Bill Formulas
Dollar discount = Face value − Purchase price
Discount yield = (Discount / Face value) × (360 / Days to maturity)
Bond-equivalent yield = (Discount / Purchase price) × (365 / Days to maturity)
Effective annual yield = (Face value / Purchase price)^(365 / Days) − 1
After-tax comparison uses federal-only tax for T-bills and combined tax for taxable alternatives
Example Scenarios
Cash Parking Decision for 6 Months
An investor deciding between a 26-week T-bill and a taxable CD can use the after-tax comparison to see which option delivers stronger net yield under current tax rates.
Laddering Short-Dated Bills
A saver building rolling 4-to-26-week maturities can compare term sensitivity to balance liquidity needs with annualized return assumptions.
High State-Tax Environment Screening
In high state-tax jurisdictions, tax exemption can materially change rankings between Treasury bills and taxable products even when nominal rates look similar.
How People Use This Calculator
- Comparing T-bills with CDs and HYSAs on an after-tax basis.
- Planning short-term reserve deployment with known maturity dates.
- Understanding yield-convention differences across fixed-income products.
- Evaluating tax-equivalent return thresholds for taxable alternatives.
- Building repeatable cash-management rules in volatile rate environments.
Treasury Bill Planning Tips
Keep convention differences in mind when comparing quotes.
Discount yield and bond-equivalent yield can look different even for the same instrument because the base and day-count assumptions differ.
Use after-tax comparison as your decision anchor in taxable accounts.
A slightly lower headline rate can still be a better choice once state and local tax treatment is incorporated.
Match term to real liquidity needs.
Chasing the top annualized figure is less helpful if the maturity date does not line up with your cash-use timeline.
Frequently Asked Questions
What is the difference between discount yield and bond-equivalent yield?
Discount yield annualizes return on face value using a 360-day convention, while bond-equivalent yield annualizes return on purchase price using a 365-day convention. Bond-equivalent yield is often more comparable to coupon-style yields.
Why can T-bills look attractive after tax?
Treasury bill interest is generally subject to federal tax but exempt from state and local income tax in many jurisdictions. That state tax exemption can improve after-tax competitiveness against taxable alternatives like CDs or corporate bonds.
Can I use this for auction and secondary-market purchases?
Yes. You can input either purchase price directly or use discount-rate assumptions to infer price. That supports planning for auction-style pricing and secondary-market comparisons.
What maturities does this calculator support?
The tool supports 4 to 52 week terms and shows sensitivity rows across common benchmark maturities. This helps compare short-dated cash management options with a consistent framework.
Is effective annual yield the same as APY?
They are conceptually related but not always identical in presentation conventions. Effective annual yield in this calculator reflects annualized compounding implied by discount purchase and maturity value over the selected term.
What does taxable-equivalent yield mean here?
Taxable-equivalent yield is the taxable pre-tax yield required to match the Treasury bill after-tax yield under your federal and state tax assumptions. It is a useful cross-product comparison metric.
Sources and References
- U.S. TreasuryDirect educational pages on Treasury bill pricing and auctions.
- IRS guidance on federal tax treatment of U.S. Treasury interest.
- State tax authority references on Treasury interest exemptions.
- Fixed-income market convention references for day-count and yield quotation methods.