Calculate percentages, discounts, percentage change, and more — instantly and free.
Use the "What is X% of Y?" calculator. Enter 20 as the percentage and 500 as the number. Result: 20% × 500 = 100.
Use the Percentage Change calculator. Enter the old value and new value. Formula: ((New - Old) / |Old|) × 100. A positive result means an increase, negative means a decrease.
Enter the original price and discount percentage in the Discount Calculator to instantly see the amount saved and the final price.
Yes, it's completely free to use online with no login or signup required.
This free percentage calculator handles four of the most common percentage-related calculations people need in everyday life, school, and work: finding what a percentage of a number is, finding what percentage one number is of another, calculating percentage increase or decrease between two values, and calculating a discount amount and final price. Each calculator works instantly as you enter numbers, with no signup or installation required.
This is the most common percentage calculation — finding a specific percentage of a given number. For example, "what is 20% of 500?" is answered by multiplying 500 by 20 and dividing by 100, giving 100. This calculation shows up constantly in everyday contexts: calculating a tip at a restaurant, figuring out sales tax on a purchase, determining what portion of a budget a specific expense represents, or working out how much of a class scored above a certain grade threshold.
This calculation answers the reverse question — given two numbers, what percentage does one represent of the other? For example, "40 is what percent of 200?" is answered by dividing 40 by 200 and multiplying by 100, giving 20%. This is useful for figuring out things like what percentage of a project is complete, what percentage of a survey answered a certain way, or what percentage of total revenue a specific product category represents.
Percentage change measures how much a value has grown or shrunk relative to its starting point, using the formula ((New Value − Old Value) ÷ |Old Value|) × 100. A positive result indicates an increase and a negative result indicates a decrease. This calculation is fundamental in finance (tracking investment returns), business (year-over-year revenue growth), and everyday comparisons (how much a price has gone up since last year). It's important to note that percentage change is always calculated relative to the original (old) value, not the new one — which is why a value that doubles represents a 100% increase, not a 50% increase.
The discount calculator answers a very practical shopping question: given an original price and a discount percentage, what's the actual amount saved, and what's the final price after the discount is applied? This is calculated by multiplying the original price by the discount percentage (divided by 100) to get the savings amount, then subtracting that from the original price to get the final price. This is useful for comparing sale prices across stores, verifying that a checkout total correctly applied an advertised discount, or budgeting for a purchase during a sale.
Percentage math is simple in principle but easy to get subtly wrong in a few common ways. One frequent mistake is confusing percentage change with percentage point change — going from 20% to 25% is a 5 percentage point increase, but it's actually a 25% relative increase (5 ÷ 20 × 100). Another common mistake is applying percentage change in the wrong direction — a 50% decrease followed by a 50% increase does not return a value to its original number, since the second 50% is calculated on a smaller base. This calculator avoids these pitfalls by applying the standard, mathematically correct formulas consistently every time, removing the guesswork from manual calculation.
All calculations in this tool run directly in your browser using JavaScript — no numbers you enter are sent to a server or stored anywhere. This makes it safe to use for any figures, including sensitive financial or business numbers, without any privacy concern.
For quick reference, here are the four core formulas this calculator applies:
Knowing these formulas is useful even when you have a calculator handy, since it helps you sanity-check results and spot errors — for instance, recognizing that a percentage change calculation should always divide by the absolute value of the old number, not the new one, prevents a common source of confusion when working with negative starting values.