For the first example (and to keep things simple), assume that imputed interest compounds annually.
Say you want to purchase a bond with a face value of $10,000, 10 years to maturity, and 5% imputed interest. To find the current price of the bond, you'd follow the formula:
Price of Zero-Coupon Bond = Face Value / (1+ interest rate) ^ time to maturity
Price of Zero-Coupon Bond = $10,000 / (1.05) ^ 10 = $6,139.11
This means that given the above variables, you'd be able to purchase a bond for $6,139.11, wait 10 years, and redeem it for $10,000. Remember that the market price of the bond will fluctuate -- possibly significantly -- over the remaining life of the bond.
Example 2
In a second example, assume that imputed interest compounds semiannually.
Price of Zero-Coupon Bond = Face Value / (1+ interest rate/2) ^ time to maturity*2
Price of Zero-Coupon Bond = $10,000 / (1.025) ^ 20 = $6,102.77
With semiannual compounding, we see the bond offered at an initially deeper discount than if imputed interest were to compound annually. Zero-coupon bonds, again, do not actually pay interest out as time passes but instead generate phantom income that is only actually paid when the bond finally matures.
Most zero-coupon bonds compound semiannually, so the second formula is more applicable for general calculation purposes.
Also, because they do not generate regular interest payments, zero-coupon bonds do not carry reinvestment rate risk -- a risk found with most other types of bonds.