The return a bond provides to an investor is measured by its yield, which is quoted as a percentage.
Current yield is a commonly quoted yield calculation, used to evaluate the return on a bond for a oneyear period. It only accounts for the interest, or coupon payments, that the bond returns to investors. This yield is calculated as the bond's coupon rate divided by its current market price, but it does nothing to account for any capital gains or losses when the bond is sold. If the bond is not sold within the year, this yield calculation will provide the bondholder with an accurate assessment of his or her return. The only way a bond's current yield could be negative, using this basic evaluation, is if the investor were receiving negative interest payments, or if the bond somehow had a market value below $0  both of which are very unlikely to occur.
Other yield calculations will take into account different factors and can be used to better evaluate the returns an investor may receive, given different events.
As its name suggests, the yield to maturity (YTM) calculates the return (expressed as an annual percentage) on a bond if the investor were to hold the bond until maturity. This formula takes into account all of the coupon payments and the face  or par  value on the bond (assuming no principal defaults), and it can be seen as a more complete evaluation than current yield. However, calculating a bond's YTM is complex and involves trial and error. It is usually done by using a programmable business calculator, but you can also get an approximate YTM by using a bond yield table.
Let's consider an example: say an investor pays $800 for a bond that has has exactly two years to maturity, a face value of $1,000 and interest payments of $8 per year. Using a bond table, we could determine that the bond will have a YTM of about 10.86%. If the bond holder paid $1,200 for the bond, the YTM would be about 9.41% (It is worth noting, however, that a bond will not necessarily have a negative actual yield just because the investor paid more than face value for it.) When using the YTM calculation, it is possible to have a negative yield on a bond  it depends largely on how much you initially pay for the bond and the time to maturity.
Yields can be calculated using different formulas  there are many more than the two mentioned here  and depending on the formula used, you can end up with drastically different yields. To learn more, see our Bond Basics Tutorial, Advanced Bond Concepts and The Basics Of The Bond Ladder.

What does a negative bond yield mean?
Find out what it means when a bond has a negative yield and what circumstances must arise for the yield to be negative when ... Read Answer >> 
What is the relationship between current yield and yield to maturity (YTM)?
Learn about the relationship between a bond's current yield and its yield to maturity, including how the market price of ... Read Answer >> 
On what basis does the sustainable growth rate fluctuate?
Learn about the differences between the calculations for the yield to maturity and spot rate for determining the present ... Read Answer >> 
What is the difference between yield to maturity and the spot rate?
Find out how yield to maturity and spot rate calculations use different discount rates to determine the present market value ... Read Answer >> 
How do I use the holding period return yield to evaluate my bond portfolio?
Find out how to use the holding period return yield formula to evaluate the performance of bonds in your portfolio, and view ... Read Answer >>

Investing
Understanding the Different Types of Bond Yields
Any investor, private or institutional, should be aware of the diverse types and calculations of bond yields before an actual investment. 
Investing
Bond Yields: Current Yield And YTM
A bond's current yield, also called "bond yield," is the interest it pays annually divided by the bond's price. A stock's current yield, also called "dividend yield," is the sum of its annual ... 
Investing
Understanding Bond Prices and Yields
Understanding this relationship can help an investor in any market. 
Financial Advisor
Simple Math for FixedCoupon Corporate Bonds
A guide to help to understand the simple math behind fixedcoupon corporate bonds. 
Investing
Understanding Interest Rates, Inflation And Bonds
Get to know the relationships that determine a bond's price and its payout. 
Managing Wealth
How Bond Prices and Yields Work
Understanding bond prices and yields can help any investor in any market. 
Investing
How To Evaluate Bond Performance
Learn about how investors should evaluate bond performance. See how the maturity of a bond can impact its exposure to interest rate risk. 
Investing
Find The Right Bond At The Right Time
Find out which bonds you should be investing in and when you should be buying them. 
Investing
Corporate Bond Basics: Learn to Invest
Understand the basics of corporate bonds to increase your chances of positive returns.

Yield To Maturity (YTM)
The total return anticipated on a bond if the bond is held until ... 
Current Yield
Annual income (interest or dividends) divided by the current ... 
Bond Yield
The amount of return an investor will realize on a bond. Several ... 
Required Yield
The return a bond must offer in order to be a worthwhile investment. ... 
Bond
A debt investment in which an investor loans money to an entity ... 
Discount Bond
A bond that is issued for less than its par (or face) value, ...