Municipal bonds, or munis, are an investment option some individuals like to use because bond values may be exempt from federal and state income tax, depending on the type of bond. Based on the fact that several government organizations issue bonds as a way to raise funds for public projects like schools, sewer systems, highways, housing, and hospitals, some view munis as safe investments.

With bond values, the face value remains the same regardless of the interest rate. The face value is the principal, or the original amount, you invested when you purchased the bond. The face value also indicates whether or a not a bond is selling at a premium amount, which means the bond values are higher than the principal amount. Discounted munis mean the seller is letting the bond go for less than the principal investment.

While many bonds have a set interest rate and pay investors the earned interest on a semi-annual basis, there are other types of bonds. Floating rate bonds and zero coupon bonds can affect bond values because the interest rates fluctuate based on predetermined benchmark interest rate indexes. With zero coupon bonds, you don't receive a payment until the bond matures, at which point you get the face value plus any compounded interest.

Since bond values may change based on the interest rate, you may want to use online resources to track future values. Online bond values calculators allow you to enter the information for a specific bond into the template in order to get an estimated value. If you have an idea of the factors affecting the value, this can be a quick way to determine the value. Some investors also use bond indices to determine the yield, duration, and final value for a bond.