Percentage Calculator
Percentages appear in almost every domain of business and daily life: discounts, profit margins, tax rates, interest, tips, statistics, performance metrics, and more. Despite being a fundamental concept, percentage calculations trip up even experienced professionals — especially when working backwards from a result, or when dealing with percentage change versus percentage point differences. This calculator covers the three most common percentage operations in a single tool.
Mode 1 finds the amount: what is 15% of 200? (Answer: 30.) Mode 2 finds the rate: 45 is what percentage of 180? (Answer: 25%.) Mode 3 finds the whole: if 30 represents 12% of something, what is the total? (Answer: 250.) Each mode uses the same underlying relationship between part, whole, and percentage — the calculator rearranges the formula to solve for whichever value you need. Every result shows the formula so you can verify or reproduce the calculation in a spreadsheet.
Percentage calculations are the foundation of many other financial metrics. Profit margin is profit as a percentage of revenue. VAT is a percentage of the net price. Discount is a percentage of the original price. Sales growth is the percentage change from last year. By understanding how to compute percentages fluently in both directions, you gain the ability to quickly sanity-check figures that appear in spreadsheets, invoices, reports, and proposals — an essential skill in any analytical or commercial role.
Formula
Amount = Total × (Percent ÷ 100) Percent = (Part ÷ Total) × 100 Whole = Part ÷ (Percent ÷ 100)
All three percentage calculations use the same relationship: Percent × Total = Part × 100. Rearrange for what you need: to find the amount multiply total by the rate; to find the rate divide part by total; to find the whole divide part by the rate.
Worked Examples
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 200 = 200 × 0.15 = 30. Equivalently, move the decimal point two places left and multiply: 15% = 0.15, and 0.15 × 200 = 30. This works for any percentage and any number, including decimals.
How do I find what percentage one number is of another?▾
Divide the part by the whole, then multiply by 100. For example, 45 out of 180 = (45 ÷ 180) × 100 = 25%. This formula is also used for profit margin (profit ÷ revenue × 100), completion rates, and any situation where you need to express one quantity relative to another as a percentage.
How do I find the original number before a percentage was taken?▾
Divide the known part by the percentage rate (as a decimal). If 30 represents 12% of something: 30 ÷ 0.12 = 250. This is the reverse percentage calculation. It is also used to find the original price before a discount: if you paid £76 after a 5% discount, the original price is £76 ÷ 0.95 = £80.
What is the difference between percentage and percentage points?▾
A percentage is a proportion of a total. A percentage point is the arithmetic difference between two percentages. If a tax rate goes from 10% to 15%, it increased by 5 percentage points — but the relative change (percentage change) is 50%, because 5 is 50% of 10. In financial reporting, mixing up percentage change and percentage points is a common source of misleading statements.
How do I calculate percentage increase or decrease?▾
Use the Percentage Change Calculator for increases and decreases. The formula is: ((new − old) ÷ |old|) × 100. A positive result means increase; a negative result means decrease. This is different from finding a percentage of a number — it measures how much something changed relative to its starting point.
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All calculations are for informational purposes only. They should not replace professional financial, tax, or legal advice. Always consult a qualified professional for decisions affecting your finances or business.