1 Month Treasury Bill Calculator

Calculate Discount Price, Yield, and Returns for 4-Week T-Bills

What is a 1 Month Treasury Bill Calculator?

A 1 month treasury bill calculator is a specialized financial tool designed to help investors determine the cost and return of 4-week US Treasury bills. Unlike traditional bonds that pay regular interest, Treasury Bills (T-Bills) are “zero-coupon” securities. They are sold at a discount to their face value. Your profit comes from the difference between the discounted price you pay and the full face value you receive when the bill matures.

Using a 1 month treasury bill calculator is essential for individual investors, corporate treasurers, and institutional desks who need to compare the Investment Yield (also known as the Bond Equivalent Yield) against other short-term cash vehicles like Money Market Accounts or CDs. By inputting the auctioned discount rate, this tool provides the exact purchase price and the true annual yield of the investment.

Many beginners mistakenly assume the “Discount Rate” is the same as the “Yield.” However, because the discount is calculated on the face value rather than your actual out-of-pocket cost, the yield is always slightly higher. This calculator clarifies that discrepancy immediately.

1 Month Treasury Bill Calculator Formula and Mathematical Explanation

The mathematics behind the 1 month treasury bill calculator involves two distinct stages: calculating the purchase price based on the bank’s discount method and then converting that into a standard investment yield.

1. Purchase Price Formula

The U.S. Treasury uses a 360-day year (the “banker’s year”) to determine the discount amount:

Price = Face Value × [1 – (Discount Rate × Days to Maturity / 360)]

2. Bond Equivalent Yield (BEY) Formula

To compare a T-Bill to a traditional bond or savings account, we use a 365-day year and calculate the return based on the purchase price:

BEY = [(Face Value – Price) / Price] × (365 / Days to Maturity)

Variable	Meaning	Unit	Typical Range
Face Value	Amount paid back at maturity	USD ($)	$100 – $10,000,000+
Discount Rate	Annualized auction rate	Percentage (%)	0.01% – 5.50%
Days to Maturity	Term length	Days	28 (standard)
Purchase Price	What you pay today	USD ($)	< Face Value

Practical Examples (Real-World Use Cases)

Example 1: The Standard $10,000 Investment

An investor wants to use the 1 month treasury bill calculator for a $10,000 face value bill at a 5.20% discount rate with 28 days to maturity.

• Input Face Value: $10,000
• Input Rate: 5.20%
• Output Price: $9,959.56
• Total Profit: $40.44
• BEY (Yield): 5.293%

In this case, the investor “earns” $40.44 over 28 days, which results in a yield higher than the discount rate.

Example 2: Institutional Cash Management

A small business has $100,000 in excess cash. They see a 1-month auction rate of 5.45%.

• Input Face Value: $100,000
• Input Rate: 5.45%
• Output Price: $99,576.11
• Total Profit: $423.89
• BEY (Yield): 5.549%

By using the 1 month treasury bill calculator, the treasurer sees that the true yield is roughly 5.55%, making it more attractive than a 5.30% high-yield savings account.

How to Use This 1 Month Treasury Bill Calculator

1. Enter Face Value: Type in the total amount you want to receive when the T-Bill matures. Most TreasuryDirect purchases are in multiples of $100.
2. Input the Discount Rate: Check the latest auction results from the Treasury Department and enter the high discount rate.
3. Set Maturity Days: For a 1-month bill, this is typically 28 days, but it may vary slightly during holiday weeks.
4. Review Results: The 1 month treasury bill calculator will update in real-time, showing the Purchase Price, Total Discount (your profit), and the Investment Yield.
5. Analyze the Chart: Use the visual breakdown to see how much of your total maturity value is original capital versus interest gain.

Key Factors That Affect 1 Month Treasury Bill Results

• Federal Reserve Policy: The FOMC sets the federal funds rate, which directly influences the auction rates for 1-month T-bills.
• Inflation Expectations: If inflation is expected to rise, investors demand higher discount rates, lowering the purchase price.
• Liquidity Needs: As the shortest-term Treasury security, 1-month bills are highly liquid, which sometimes results in lower yields than 6-month or 1-year bills.
• Taxation: While subject to federal income tax, T-Bill interest is exempt from state and local taxes, increasing the “effective” yield for residents of high-tax states.
• Market Demand: High demand at auction (bid-to-cover ratio) can drive down the discount rate, increasing the purchase price.
• Reinvestment Risk: Because the term is only 28 days, you face the risk that rates might be lower when you try to roll the funds into a new bill next month.

Frequently Asked Questions (FAQ)

Why is the yield (BEY) higher than the discount rate?

The discount rate is calculated as a percentage of the Face Value using a 360-day year. The Yield (BEY) is calculated as a percentage of the Purchase Price using a 365-day year. Since the purchase price is lower than the face value and the year is longer, the yield is mathematically higher.

Is a 1-month Treasury Bill 30 days or 28 days?

In the US Treasury market, the “1-month” bill is technically a 4-week bill, meaning its standard term is 28 days from issuance to maturity.

How often are 1-month T-Bills auctioned?

The US Treasury typically auctions 4-week bills every week, usually on Thursdays, with issuance on the following Tuesday.

Do I pay state taxes on T-Bill gains?

No. One of the biggest advantages of using the 1 month treasury bill calculator to plan investments is that the interest is exempt from state and local income taxes.

Can I sell a 1-month T-Bill before maturity?

Yes, they are highly liquid and can be sold on the secondary market, though you may receive more or less than your purchase price depending on current interest rates.

What is the minimum investment for a T-Bill?

The minimum purchase amount through TreasuryDirect or most brokers is $100.

What happens if the discount rate is zero?

If the rate is 0%, the 1 month treasury bill calculator will show the purchase price is equal to the face value, meaning you earn no interest.

Is my money safe in a 1-month T-Bill?

Treasury bills are backed by the full faith and credit of the U.S. government and are considered one of the safest investments in the world.