Percentage Calculator

How to Use the Percentage Calculator

Pick the question you want answered, type your two numbers into the sentence, and the percentage calculator shows the answer instantly with the working. It covers the seven everyday percentage questions: a percentage of a number, what percentage one number is of another, finding the whole from a percentage, percentage increase or decrease, adding a percentage, subtracting a percentage (such as a discount), and working back to the original value.

Percentage Formulas

Percentage Calculator Examples

Everyday Uses: Discounts, GST, Marks and Pay Rises

• Discounts: 30% off a $1,299 TV is $1,299 × 0.70 = $909.30, a saving of $389.70.
• GST: adding 10% GST to $59.99 gives $65.99 (rounded), and a GST-inclusive price of $110 was $100 before GST. For invoices, the GST calculator shows the GST amount separately.
• Exam marks: 42 out of 50 is 84%. To combine assessments worth different amounts, use the weighted average calculator or the grade percentage calculator.
• Pay rises and prices: a salary going from $80,000 to $83,500 is a 4.375% increase. For more on changes over time, the percentage change calculator also does percentage difference, percentage points and average change per year.
• Profit margin: an item bought for $40 and sold for $50 makes $10 profit, which is a 25% markup on cost but a 20% margin on the sale price — two different percentages of the same $10.

More Than 100% and Negative Percentages

100% means the whole amount. A percentage above 100% means more than the whole: 300 is 250% of 120. A negative percentage change means the value went down. A 100% decrease takes anything to zero, but an increase can be any size — a value that doubles has risen by 100%, and one that triples has risen by 200%.

Frequently Asked Questions

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. For example, 15% of 80 is 0.15 × 80 = 12. In the calculator, choose 'What is X% of Y?' and enter 15 and 80.

How do I work out what percentage one number is of another?

Divide the part by the whole and multiply by 100. 50 out of 200 is 50 ÷ 200 × 100 = 25%. This is also how you turn a test score into a percentage: 42 out of 50 is 84%.

How do I calculate a percentage increase or decrease?

Subtract the old value from the new value, divide by the old value and multiply by 100. From 80 to 92 is (92 − 80) ÷ 80 × 100 = a 15% increase. A negative answer is a decrease: 250 down to 200 is −20%.

How do I add 10% to a number?

Multiply the number by 1.10. 200 plus 10% is 200 × 1.1 = 220. This works for any percentage: to add 15%, multiply by 1.15. Adding 10% GST to a price works the same way.

How do I subtract a percentage from a number, such as a discount?

Multiply by 1 minus the percentage as a decimal. 25% off 120 is 120 × 0.75 = 90, and 30% off $1,299 is $909.30. The amount saved is the difference: $389.70.

How do I find the original number before a percentage was added?

Divide the final number by 1 plus the percentage as a decimal. If 220 is the price after a 10% increase, the original was 220 ÷ 1.1 = 200. Don't subtract 10% of 220 — that gives 198, which is wrong because the 10% was taken from the original, not the final price.

How do I find the original price before a discount?

Divide the sale price by 1 minus the discount as a decimal. An item that costs $68 after 15% off was originally $68 ÷ 0.85 = $80. Choose 'Find the original value' and select 'A decrease'.

X is Y% of what number?

Divide X by the percentage as a decimal. If 30 is 20% of a number, the number is 30 ÷ 0.2 = 150. This is useful for working out a total from a known share, such as a deposit that is 20% of a property price.

Why doesn't adding and then subtracting the same percentage get back to the start?

Each percentage is taken from a different base. 100 plus 10% is 110, but 10% off 110 takes away 11, leaving 99 — a net 1% loss. To undo a 10% increase you need a decrease of about 9.09%.

What is the difference between a percentage and a percentage point?

Percentage points are the simple difference between two percentages. An interest rate moving from 4% to 5% has risen 1 percentage point, but that is a 25% increase in the rate itself. Use the percentage change calculator's percentage points mode to work out both.