Determine the amount of change in the numbers. Subtract the old amount from the new amount. For example, if it took you 45 minutes to drive to work today and 30 minutes to drive to work yesterday, subtract 30 from 45 to obtain a change of 15 minutes.
Divide the amount of change by the original amount. In our example, divide 15 by 30 to obtain .5.
Multiply by 100 to convert the result to a percentage. When you multiply .5 by 100, the result is 50. Therefore, your drive time increased by 50 percent from yesterday to today.