The usual way of calculating interest — as a percentage of the sum borrowed.
Examples from the Web for interest rate
UBS is the second bank to make a major settlement for interest-rate manipulation.Speed Read: The Juiciest Bits From the UBS LIBOR Settlement |Matthew Zeitlin|December 19, 2012|DAILY BEAST
Only those with money in a LIBOR-based security: a pension fund, a corporate bond, an interest-rate swap, a home loan.
Only in the mid-1990s did the central bank begin to publicly announce changes in interest-rate policy.
This capital is lent at an interest-rate of from ten to twelve per cent.The Philippine Islands|Ramon Reyes Lala