How to use the function DISC() in Excel and other spreadsheet tools for US Treasury Bills?

DISC() is a function provided in Microsoft Excel, Apache OpenOffice and other spreadsheet tools. It allows you to calculate the discount rate of a debt security.

=DISC(settlement, maturity, price, redemption, basis)

where:
  settlement = the settlement date after purchasing the security
  maturity = the maturity date of the security
  price = the purchase price 
  redemption = the redemption value 
  basis = the day count basis:
    0: US (NASD) 30/360
    1: Actual/actual
    2: Actual/360
    3: Actual/365
    4: European 30/360

You can try to apply the DISC() to a US Treasury Bill (T-Bill) by setting:

redemption = $100.00 
basis = 2: Actual/360

1. Start Excel or other spreadsheet tool.

2. Enter the following formula in a cell:

=DISC("2024-12-26", "2025-06-26", 97.891833, 100.0, 2)

3. Take the output:

0.041700007 (4.1700% as the discount rate)

4. Compare it with the following T-Bill transaction example:

CUSIP: 912797NW3
Type: 26-Week Bill 
Par Amount: $10,000.00 (Face value) 
Purchase Price: $9,789.18

Investment/Interest Rate: 4.319% (BEY - Bond Equivalent Yield)
Yield: 4.170% (Discount rate)
Price per $100: 97.891833

Discount: $210.82

Issue Date: 2024-12-26 (Settlement date)
Maturity Date: 2025-06-26

As you can see, the output of the DISC() function matches well with the discount rate in this example.

You can also use our online calculator to validate the result. Click this link "T-Bill 912797NW3 settled on 2024-12-26 with a purchase price of $97.891833, you will see the discount rate of 4.1700% displayed.

You can also try the following 52-week T-Bill:

Term and Type of Security: 364-Day Bill 
CUSIP: 912797QD

High Rate: 3.820% (Discount rate)
Price: 96.137556
Investment Rate: 3.989% (BEY - Bond Equivalent Yield)

Issue Date: 2025-04-17
Maturity Date: 2026-04-16

Enter the following formula in a cell:

=DISC("2025-04-17", "2026-04-16", 96.137556, 100.0, 2)

output:
  0.038199996 (3.8200% as the discount rate)

As you can see, the output of the DISC() function matches well with the discount rate in this example.

You can also use our online calculator to validate the result. Click this link "T-Bill 912797NW3 settled on 2025-04-17 with a purchase price of $96.137556, you will see the discount rate of 3.8200% displayed.

⇒ YIELD() Spreadsheet Function for T-Bill

⇐ TBILLYIELD() Spreadsheet Function for T-Bill

⇑ Spreadsheet Functions for T-Bill

⇑⇑ US Treasury Securities