Subtract, divide, and multiply your way to successfully determining how much that increase or decrease really amounts to.
Step 1: Subtract the past number from the current number Subtract the past number from the current number. For example if the price of gas this year was $3.25 a gallon and last year it was $2.75 a gallon calculate $3.25 minus $2.75 to equal $0.50.
TIP: To calculate the predicted percent increase or decrease, subtract the current amount from the future predicted amount.
Step 2: Divide Divide the past number from the subtracted amount. From the earlier example, divide $0.50 by $2.75 to equal .1818. Use a calculator if your division skills need sharpening.
Step 3: Multiply by 100 Multiply the final number by 100. In the example, the end result equals 18.18.
Step 4: Add a percent sign Add a percent sign to the end to finish your calculated percent growth. Our example ends in 18.18 percent.
TIP: If the final number is negative, the result would be a decline, not a growth.
Step 5: Round up or down Round up if the number is five or over and round down if the number is under five. Rounding to the first decimal would equal 18.2 percent or to the nearest whole number, 18 percent.
FACT: French mathematician Blaise Pascal invented the first adding machine in 1642. It could only perform the mathematical equations of addition and subtraction.