Percent Calculator

Four results from one pair of numbers

Entering an initial value and a percentage produces four related figures at once: the percentage amount itself, the value after adding that amount, the value after subtracting it, and a reverse calculation that treats your initial value as a portion and solves for the whole it came from.

Worked example

Enter 80 as the initial value and 25 as the percentage. The percentage amount is (80 × 25) / 100 = 20. Adding it gives 80 + 20 = 100; subtracting it gives 80 - 20 = 60. The fourth line runs the numbers in reverse: (80 / 25) × 100 = 320 — meaning if 80 is 25% of some total, that total is 320. That reverse line is handy in situations like "I paid $80, which is a 25% deposit — what's the full price?"

Increase vs. decrease in one pass

Calculating both the increased and decreased values from the same inputs saves re-entering numbers when you need to compare, for instance, a price after a markup against the same price after an equivalent markdown — note that adding then subtracting the same percentage does not return you to the original value once you're working off a changed base, a common source of confusion with percentage math.

Typical uses

Common everyday cases include a restaurant tip (percentage amount), a marked-up retail price (increased value), a discounted price (decreased value), and figuring out an original price before a percentage discount was applied (the reverse calculation).