Six Ways to Use This Percentage Calculator

This tool covers every common percentage calculation you'll encounter in daily life, school, work, or business. Each calculation shows the answer, a plain-English explanation, and the formula used — so you learn the method while getting instant results.

• X% of Y: Find a percentage of any number (discounts, tax, grades)
• What %?: Find what percentage one number is of another
• % Change: Calculate the percentage increase or decrease between two values
• Increase: Add a percentage to a number (markup, salary raise)
• Decrease: Subtract a percentage from a number (discount, depreciation)
• Tip: Calculate the tip amount and total bill

Common Percentage Calculations

Percentages in Everyday Life

Shopping and discounts

A "30% off" sale means the item costs 70% of its original price. If a jacket costs £80 with 30% off: £80 × 0.70 = £56. VAT in the UK is 20%, so a pre-tax price of £100 becomes £120 after VAT is added.

Salary and pay rises

A 5% pay rise on a £30,000 salary adds £1,500, bringing the new salary to £31,500. To calculate: £30,000 × 1.05 = £31,500. Knowing the formula helps you negotiate — a "3% raise" on £40,000 is only £1,200 per year, or £100 per month before tax.

Grades and scores

If you scored 42 out of 50 on a test: (42 ÷ 50) × 100 = 84%. Most UK universities require 40% for a pass, 50% for a 2:2, 60% for a 2:1, and 70% for a first-class degree.

Tipping

In the UK, 10-12.5% is standard for restaurants. In the US, 15-20% is expected. On a £60 meal: 12.5% tip = £7.50, making the total £67.50.

Percentage vs Percentage Points

These are different and often confused. If interest rates rise from 2% to 3%, that's a 1 percentage point increase but a 50% increase in the rate itself. In news and finance, this distinction matters. "Inflation rose by 2 percentage points" (from 3% to 5%) is very different from "inflation rose by 2%" (from 3% to 3.06%).

Percentage Change Formula Explained

Percentage change = ((New Value − Old Value) ÷ Old Value) × 100. A positive result means an increase; negative means a decrease. This formula is used everywhere: stock market returns, population growth, business revenue, weight loss tracking, and inflation rates. Always divide by the original (old) value, not the new one.

Quick Mental Percentage Tricks

• 10% of anything: Move the decimal one place left. 10% of 450 = 45.
• 5% of anything: Find 10%, then halve it. 5% of 450 = 22.50.
• 20% of anything: Find 10%, then double it. 20% of 450 = 90.
• 15% (for tips): Find 10% + half of 10%. 15% of £60 = £6 + £3 = £9.
• 25% of anything: Divide by 4. 25% of 200 = 50.
• 1% of anything: Move decimal two places left. 1% of 450 = 4.50.
• Reversibility trick: 8% of 50 = 50% of 8 = 4. Swap if one is easier.

Percentages in Finance and Business

Profit margin = (Profit ÷ Revenue) × 100. A business earning £200,000 revenue with £50,000 profit has a 25% margin. Compound interest uses percentages repeatedly: £1,000 at 5% annual interest becomes £1,050 after year one, then £1,102.50 after year two (5% of £1,050, not £1,000). Understanding compounding is essential for savings, investments, and loans.

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Frequently Asked Questions