T-Bill Calculator
Calculate treasury bill purchase price, earnings, yield, and after-tax returns based on discount rate and maturity period.
Minimum $1,000 — T-Bills are sold in $1,000 increments on TreasuryDirect.
Current rates: check TreasuryDirect.gov for the latest auction results.
Choose your T-Bill duration. Auctioned weekly by the U.S. Treasury.
Common brackets: 10%, 12%, 22%, 24%, 32%, 35%, 37%. T-Bills are exempt from state & local tax — only federal tax applies.
What is a Treasury Bill (T-Bill)?
A Treasury Bill (T-Bill) is a short-term U.S. government security sold at a discount and redeemed at full face value at maturity. The difference between the purchase price and face value is your profit. T-Bills are backed by the U.S. government and considered one of the safest investments available.
How T-Bill Calculation Works
T-Bills use a bank-discount basis with a 360-day year (standard U.S. Treasury convention):
- Discount = Face Value × (Discount Rate / 100) × (Days / 360)
- Purchase Price = Face Value − Discount
- Annualized Yield = (Discount / Purchase Price) × (365 / Days) × 100
Note: The discount is calculated on a 360-day basis, but the annualized yield uses 365 days — this is the standard U.S. Treasury method.
T-Bill Tax Treatment
T-Bill earnings are subject to federal income tax but are exempt from state and local taxes. This tax advantage makes T-Bills more attractive than CDs or savings accounts for investors in high state-tax states like California, New York, or New Jersey.
T-Bill Duration Guide
T-Bills are available in six standard durations. Choose the one that best fits your cash needs:
| Duration | Days | Best For | Calculator |
|---|---|---|---|
| 4-Week | 28 | Maximum flexibility | 4-Week Calculator |
| 8-Week | 56 | Short-term cash parking | Use this calculator |
| 13-Week | 91 | Beginners, quarterly planning | 13-Week Calculator |
| 17-Week | 119 | Flexible mid-term | Use this calculator |
| 26-Week | 182 | Most popular — best balance | 6-Month Calculator |
| 52-Week | 364 | Maximum yield | 1-Year Calculator |
Not sure which duration to pick? Read our Best T-Bill Duration Guide for a full breakdown including how the rate environment affects your choice.
Compare T-Bills With Other Investments
T-Bills are one of several safe short-term options. Use these calculators to see which wins after taxes:
Learn more: What Are Treasury Bills — Complete Guide · Are T-Bills Worth It? · How Much Can I Earn from T-Bills?
Frequently Asked Questions
How does the T-Bill calculator work?
Enter your face value, discount rate, and duration. The calculator uses the U.S. Treasury bank-discount formula (360-day year) to compute your purchase price, discount earned, and annualized yield. The yield is expressed on a 365-day basis for easy comparison with other investments.
What is the difference between discount rate and yield?
The discount rate is applied to the face value on a 360-day basis — it is used to price the T-Bill at auction. The yield is calculated on the lower purchase price on a 365-day basis. Yield is always slightly higher than the discount rate. For example, a 5% discount rate on a 182-day T-Bill produces an annualized yield of approximately 5.20%.
Is the T-Bill calculator accurate?
Yes. The calculator uses the official U.S. Treasury bank-discount formula: Discount = Face Value × (Rate / 100) × (Days / 360). This is the same method used by TreasuryDirect and major brokerages to price T-Bills.
What face value should I enter?
Enter the amount you want to receive at maturity. T-Bills are sold in $100 increments with a minimum of $100 on TreasuryDirect. Most individual investors use amounts like $10,000 or $25,000.
Where do I find the current discount rate?
Check the latest auction results at TreasuryDirect.gov under 'Auction Results'. Rates change weekly with each auction. Major brokerages like Fidelity and Schwab also display current T-Bill rates in their fixed income sections.