Percentage Calculations

Percentage Calculations

Percentages are one of the most common everyday math operations. While the evaluator does not have a dedicated % percent operator (the % symbol means modulo), you can express any percentage calculation as a simple expression.

Percentage of a Value

"What is X% of Y?" translates to:

X / 100 * Y

Examples:

15 / 100 * 200 = 30     (15% of 200)
7.5 / 100 * 80 = 6      (7.5% of 80)
0.5 / 100 * 1000 = 5    (0.5% of 1000)

Percentage Change

"What is the percentage change from A to B?"

((B - A) / abs(A)) * 100

Example: price went from 50 to 65:

((65 - 50) / abs(50)) * 100 = 30

That is a 30% increase.

Adding/Removing a Percentage

Adding tax (e.g., 8.5% sales tax to a $49.99 item):

49.99 * (1 + 8.5/100) = 54.239

Discount (e.g., 25% off $120):

120 * (1 - 25/100) = 90

Finding the Original Before Tax

If the final price including 20% tax is 240, the original is:

240 / (1 + 20/100) = 200

Tip Calculator

A quick 18% tip on a $75 meal:

75 * 18 / 100 = 13.5