How to Use the TBILLPRICE and TBILLYIELD Functions in Google Sheets for Treasury Bill Valuation

Short-term sovereign debt securities, such as US Treasury bills (T-bills), do not pay periodic coupon interest. Instead, they are issued at a discount to their par value and mature at full face value. Valuing these instruments in Google Sheets requires specialised financial math rather than standard compound bond formulas. Google Sheets provides two tailored functions for this exact purpose: TBILLPRICE and TBILLYIELD.

Understanding Discount Securities in Financial Spreadsheets

Because Treasury bills have maturities ranging from four weeks to a maximum of one year (52 weeks), their pricing conventions adhere to money market accounting rules:

• Discount Basis: T-bills trade on a discount rate basis using an actual/360 day-count convention.
• Maturity Restrictions: Both TBILLPRICE and TBILLYIELD require that the maturity date occurs within exactly one calendar year (365 days, or 366 in leap years) of the settlement date. If the duration exceeds one year, Google Sheets returns an immediate #NUM! error.
• Standard Face Value: The pricing formula outputs the monetary cost per $100 face value. For instance, a price output of 97.50 signifies an investor pays $975 for a $1,000 par bond.

Syntax and Argument Structure

The syntax for both Treasury bill functions is structured as follows:

=TBILLPRICE(settlement, maturity, discount)
=TBILLYIELD(settlement, maturity, price)

Parameter	Data Type	Function Used In	Description
settlement	Date	Both	The settlement date when the Treasury bill is acquired.
maturity	Date	Both	The date on which the Treasury bill matures (must be within 1 year).
discount	Percentage / Decimal	TBILLPRICE	The annualised discount rate expressed as a decimal (e.g., 0.052 for 5.2%).
price	Numeric / Currency	TBILLYIELD	The purchase price per $100 face value.

How to Calculate Treasury Bill Price with TBILLPRICE

To evaluate what you must pay for a newly auctioned or secondary-market Treasury bill:

1. Open Google Sheets and enter your transaction parameters in cells A1:B3:
   • Settlement Date (B1): 01/06/2026 (Formatted as Date)
   • Maturity Date (B2): 01/12/2026 (6-month T-bill)
   • Discount Rate (B3): 0.048 (4.8% discount rate)
2. Select an empty target cell (e.g., B5).
3. Enter the formula:

   =TBILLPRICE(B1, B2, B3)

4. Press Enter. Google Sheets calculates the holding period discount based on the 360-day money market year and displays the price per $100 par value (e.g., $97.56).

How to Calculate Annualised Yield with TBILLYIELD

When comparing Treasury bills against high-yield savings accounts or commercial paper, investors need to convert the discounted purchase price into an annualised bond yield:

1. Enter the settlement and maturity dates in cells B1:B2.
2. Enter the quoted market price per $100 in cell B4 (e.g., 97.50).
3. In target cell B6, type:

   =TBILLYIELD(B1, B2, B4)

4. Press Enter.
5. Format cell B6 as a percentage (Format > Number > Percent) to reveal the annualised rate of return.

Troubleshooting Common Errors

Error Message	Root Cause	Remediation Step
#NUM!	The maturity date is more than one year (365 days) after settlement.	Verify your security dates; for longer maturities, use the PRICE or YIELD function instead.
#NUM!	Discount rate or price is less than or equal to zero.	Confirm that the price or discount rate parameter contains a positive numeric value.
#VALUE!	Dates are entered as plain text strings that Google Sheets cannot parse.	Convert date cells to valid dates using the DATE(year, month, day) function.