Percentage Calculator

How to use

Each box above is a separate mode — just fill in the one you need and the answer appears as you type. Use What is X% of a number for tips, taxes, and "how much is 15% of this". Use X is what percent of Y when you have two numbers and want the ratio, like a test score. The percentage increase / decrease mode compares an old and a new value — perfect for price changes, salary raises, follower counts, or anything that went up or down over time. And the discount mode works both ways: enter the original and sale price to get the discount percentage, or the original price and a discount percentage to get what you would pay.

The formulas

A percentage is just a ratio out of 100. These four formulas cover almost every everyday situation:

• X% of a number = number × (X ÷ 100)
• X as a percent of Y = (X ÷ Y) × 100
• Percentage increase / decrease = (new − old) ÷ old × 100 — positive means an increase, negative means a decrease
• Discount = (original − sale) ÷ original × 100, and sale price = original × (1 − discount ÷ 100)

One thing that trips people up with increases and decreases: the change is always measured against the old value. Going from 40,000 to 50,000 is a 25% increase, but going back from 50,000 to 40,000 is only a 20% decrease — same 10,000 difference, different base.

Examples

What is 15% of 50,000? That's 50,000 × 0.15 = 7,500 — so a 15% discount on a 50,000 item saves you 7,500 and you pay 42,500. If you got 30 questions right out of 120, your score is (30 ÷ 120) × 100 = 25%. If your rent went from 40,000 to 50,000, that's (50,000 − 40,000) ÷ 40,000 × 100 = a 25% increase; if a stock fell from 50,000 to 42,500, that's (42,500 − 50,000) ÷ 50,000 × 100 = a 15% decrease. And if a 50,000 item is on sale for 39,900, the discount is (50,000 − 39,900) ÷ 50,000 × 100 = 20.2% off.

Frequently asked questions

How do I calculate a percentage of a number?

Multiply the number by the percentage divided by 100. For example, 15% of 50,000 is 50,000 × 0.15 = 7,500.

How do I calculate percentage increase or decrease?

Take (new value − old value) ÷ old value × 100. For example, going from 40,000 to 50,000 is (50,000 − 40,000) ÷ 40,000 × 100 = a 25% increase. A negative result means a decrease. If the old value is 0, the percentage change is undefined — there is no base to compare against.

How do I calculate a discount percentage?

Take (original price − sale price) ÷ original price × 100. If a 50,000 item sells for 39,900, that's (50,000 − 39,900) ÷ 50,000 × 100 = 20.2% off. Going the other way, sale price = original price × (1 − discount ÷ 100). In the discount mode above, entering the original and sale price gives you the discount percentage, while entering the original price and a discount percentage gives you the sale price.

Is anything I type sent to a server?

No. All calculations run entirely in your browser, and nothing you type is ever sent to or stored on a server.