where 
in finance the calculation for roc can also be computed as a return over time in this instance the formula uses the current value of a stock or index and divides it by the value from an earlier period subtract one and multiply the resulting number by 100 to give it a percentage representation r o c current value previous value 1 100 roc frac text current value text previous value 1 100 roc previous valuecurrent value 1 100the price rate of change indicatorthe rate of change is most often used to measure the change in a security s price over time this is also known as the price rate of change also abbreviated roc the price rate of change can be derived by taking the price of a security at time b minus the price of the same security at time a and dividing that result by the price at time a 2price roc b a a 100 where b price at current time a price at previous time begin aligned text price roc frac b a a times 100 textbf where b text price at current time a text price at previous time end aligned price roc ab a 100where b price at current timea price at previous time the indicator is an unbounded momentum indicator used in technical analysis set against a zero level midpoint when it is positive prices are accelerating upward when negative downward 