Percentage Calculator

The all-in-one percentage calculator

Percentages come up everywhere — a tip at a restaurant, a discount in a sale, a test score, a price rise, or a change in a statistic. This free percentage calculator brings the five most useful percentage calculations together in one place, so you can get an accurate answer in seconds without reaching for a formula or a spreadsheet.

How to calculate a percentage of a number

To find a percentage of a number, multiply the number by the percentage and divide by 100. For example, to work out 15% of 200 you calculate 200 × 15 ÷ 100 = 30. The Percent of tab does this instantly — just enter the percentage and the value.

How to calculate percentage change

Percentage change measures how much a value has gone up or down relative to where it started. Subtract the original value from the new value, divide by the original value, and multiply by 100. A positive answer is a percentage increase and a negative answer is a percentage decrease. This is ideal for price changes, growth rates, and comparing before-and-after numbers.

How to calculate a tip

The tip calculator multiplies your bill by the tip percentage to find the tip amount, adds it to the bill for the total, and divides by the number of people so you know exactly what each person owes. It makes splitting the bill quick and fair, whether you're tipping 15%, 18% or 20%.

How to calculate a discount

The discount calculator shows the sale price and your savings. Enter the original price and the percentage off; it multiplies the price by the discount and divides by 100 to find the saving, then subtracts that from the original price for the final price. It's the fastest way to answer "how much is 25% off?".

---

The formulas behind each tab

Percentages are just fractions written out of 100. That single idea drives every mode in this calculator — the only thing that changes is which two numbers you start with and which one you are trying to find.

Percent of a number

You want a slice of a whole. Multiply the whole by the percentage, then divide by 100:

result = value × percentage ÷ 100

Think of it as "percentage hundredths." 15% means 15 per hundred, so 15% of 200 is 200 × 15 ÷ 100 = 30.

X is what percent of Y?

Here you already have the part and the whole, and you need the percentage:

percentage = (part ÷ whole) × 100

If you scored 42 out of 50 on a test, the percentage is (42 ÷ 50) × 100 = 84%.

Percentage change

This measures how far a value moved relative to where it started — not relative to the new value. The original number is always the denominator:

change % = ((new − original) ÷ original) × 100

A positive answer is an increase; a negative answer is a decrease. Going from 80 to 100 is a 25% increase (because the rise of 20 is one-quarter of 80). Going from 100 to 80 is a 20% decrease (the drop of 20 is one-fifth of 100). The direction matters.

Tip and discount modes

Both are applications of "percent of." A tip is percentage × bill ÷ 100; the total with tip is bill + tip. Splitting the bill divides that total by the number of people. A discount is the same math in reverse: savings = price × discount ÷ 100, and sale price = price − savings.

Worked examples

Common mistakes to watch for

• Using the wrong base for percentage change. Always divide by the original value. A stock that doubles from $50 to $100 is a 100% gain, not a 50% gain.
• Confusing percentage points with percent. If interest rises from 3% to 5%, that is a 2 percentage point increase — but it is a 66.7% relative increase in the rate itself. Headlines often blur the two.
• Stacking discounts incorrectly. "20% off, then another 10% off" is not 30% off the original price. The second discount applies to the already-reduced price. On a $100 item: after 20% off you pay $80; 10% off that is $8, so the final price is $72 (28% off total, not 30%).
• Forgetting tax is usually on the pre-tip amount. In many places, sales tax is calculated before the tip is added. This calculator handles tip on the bill you enter — if your bill already includes tax, enter the total shown on the receipt.

When to use each tab

Use Percent of when you know the rate and the starting amount — tips, VAT estimates, "what is 6% of my salary," commission on a sale. Use X is what percent of Y when you have two finished numbers and need the ratio — test scores, "what fraction of my budget did I spend," market share.

Use Percentage change for before-and-after comparisons — price rises, population growth, year-on-year revenue. It is the wrong tool if you only need a simple slice of a number; that is Percent of. Use the Tip tab specifically when you need per-person splits, not just the tip amount. Use Discount when you have a sticker price and a percentage-off tag and want the final sale price in one step.

Because everything runs on your device, there's nothing to install and nothing is uploaded. Your numbers stay completely private, and the calculator works even when you're offline. This is one of many free browser tools on Uzetool — explore more tools as we add them.