Bond Equivalent Yield (BEY)
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Short-term money market instruments like U.S. Treasury bills and commercial paper are quoted using discount yield conventions based on a 360-day year. However, traditional corporate and government bonds pay semi-annual coupons based on a 365-day year. To compare short-term discount notes fairly against traditional coupon-bearing bonds, fixed income analysts calculate the Bond Equivalent Yield (BEY).
Our free Bond Equivalent Yield Calculator converts Treasury bill discount quotes and 360-day Money Market Yields (MMY) into standardized 365-day semi-annual annual bond yields.
How to Calculate Bond Equivalent Yield (BEY)
BEY converts a discount instrument’s return into an annualized yield using a 365-day calendar year and actual purchase price denominator.
BEY Formula for Treasury Bills (Discount Price Basis):
BEY (%) = [ ( Par Value - Purchase Price ) / Purchase Price ] × ( 365 / Days to Maturity ) × 100
BEY Formula from Money Market Yield (MMY 360-Day Conversion):
BEY (%) = Money Market Yield (%) × ( 365 / 360 )
- Par Value: Face value paid at maturity (typically $10,000 for T-Bills).
- Purchase Price: Discounted purchase price paid on open market.
- Days to Maturity: Exact number of days remaining until maturity.
Step-by-Step Treasury Bill Conversion Example
Suppose an investor purchases a 180-day Treasury bill with a $10,000 Par Value at a discounted purchase price of $9,750.00.
Let’s calculate the holding period yield, day-count annualization factor, and resulting Bond Equivalent Yield (BEY):
Dollar Discount = $10,000 - $9,750 = $250.00
Holding Period Return = $250.00 / $9,750.00 = 0.025641 (2.5641%)
Day-Count Annualization Multiplier (365 / 180) = 2.027778
BEY = 2.5641% × 2.027778 = 5.20%
| Yield Convention Standard | Calendar Basis | Price Denominator Used | Calculated Yield (%) | Comparison Standard |
|---|---|---|---|---|
| Bank Discount Yield (BDY) | 360 Days | Par Value ($10,000) | 5.00% | Quoted T-Bill discount rate |
| Money Market Yield (MMY) | 360 Days | Purchase Price ($9,750) | 5.13% | Short-term commercial paper rate |
| Bond Equivalent Yield (BEY) | 365 Days | Purchase Price ($9,750) | 5.20% BEY | Direct comparison to corporate bond YTM |
Frequently Asked Questions (FAQ)
What is Bond Equivalent Yield (BEY)?
Bond Equivalent Yield (BEY) is an annualized yield metric that allows short-term money market discount notes (quoted on a 360-day basis) to be directly compared to traditional semi-annual coupon-paying bonds (quoted on a 365-day basis).
Why is BEY always higher than the Bank Discount Yield (BDY)?
BEY is higher than BDY for two reasons: First, BEY uses actual purchase price (which is less than par value) as the denominator. Second, BEY uses a 365-day calendar year instead of a 360-day calendar year (365 / 360 = 1.01388).
When should institutional investors use BEY?
Institutional treasurers use BEY whenever they compare short-term cash holdings (Treasury bills, CDs, commercial paper) against longer-term government or corporate bonds to make optimal asset allocation decisions across fixed income asset classes.