Percentage Calculator — 4 Modes in One Tool
This free online percentage calculator handles the four most common percentage problems — find X% of Y, express X as a percentage of Y, calculate percentage change between two values, and reverse a percentage to find the original number. Students, shoppers, accountants, and marketers all use it daily.
What is X% of Y?
X is what % of Y?
% Change from X to Y
Find Original Value
How to Use This Percentage Calculator
Each mode solves a distinct problem. Results update instantly as you type, and a step-by-step formula beneath each result shows exactly how the answer was reached.
Mode A — What is X% of Y?
Multiply the percentage by the value and divide by 100. Example: 15% of 200 = (15 ÷ 100) × 200 = 30. Use the preset buttons to quickly apply common tip rates, discounts, or sales tax percentages.
Mode B — X is what % of Y?
Divide the part by the whole and multiply by 100. Example: 45 out of 60 = (45 ÷ 60) × 100 = 75%. Ideal for grades, survey response rates, and market share calculations.
Mode C — Percentage Change
Formula: ((New − Old) ÷ |Old|) × 100. A green arrow and positive number indicate an increase; red with a negative number indicates a decrease. Use it for year-over-year revenue comparisons or price movement analysis.
Mode D — Find the Original Value Before a Change
If a price is now $120 after a 20% increase, the original was $120 ÷ 1.2 = $100. For a decrease, divide by (1 − rate/100). This is the reverse percentage formula used for VAT removal and sale price analysis.
Percentage Formulas Quick Reference
- X% of Y: (X ÷ 100) × Y
- X as % of Y: (X ÷ Y) × 100
- % change: ((New − Old) ÷ Old) × 100
- Original before increase: Final ÷ (1 + Rate/100)
- Original before decrease: Final ÷ (1 − Rate/100)
Key Features
- Four independent calculation modes on a single page — no switching tabs or reloading.
- Live results: every keystroke updates the answer and the formula simultaneously.
- Step-by-step formula display so you can verify or learn the math, not just trust a black box.
- Preset buttons for the most common real-world scenarios: tip rates, tax, discounts, and score fractions.
- Copy button on each mode sends the result directly to your clipboard.
- Direction indicator (↑ green / ↓ red) on the percentage change mode for at-a-glance reading.
Use Cases
Calculate Sales Tax or VAT on a Purchase
Use Mode A to find the tax amount (e.g. 8.5% of $499). Use Mode D to reverse-calculate the pre-tax price from a tax-inclusive total — the same method that works for UK VAT, EU VAT, or Australian GST.
Analyse a Pay Rise or Investment Return
Mode C gives the exact percentage change between any two values. Enter your old salary and new salary to see the percentage increase. Enter last year's portfolio value and this year's to calculate your return.
Work Out a Test Score or Conversion Rate
Mode B turns raw numbers into percentages: 43 correct out of 50 = 86%. The same logic applies to conversion rates — 320 clicks from 8,000 impressions = 4% CTR.
Find the Original Price Before a Discount
Mode D with "decrease" selected: if a coat is now $72 after a 40% discount, the original price was $72 ÷ 0.60 = $120. Useful for verifying whether a "sale" price is genuinely discounted.
FAQ's
Percentage increase uses the original value as the base: ((New − Old) / Old) × 100. Markup uses cost as the base: (Profit / Cost) × 100. A 50% markup means you added 50% of cost to the price; the resulting gross margin (profit as % of selling price) is only 33.3% — not 50%.
Use Mode D. Enter the VAT-inclusive price as the final value, enter the VAT rate as the percentage, and select "increase". The calculator divides by (1 + rate/100). For UK 20% VAT: £120 ÷ 1.2 = £100 net. The VAT amount is £20.
Each percentage applies to a different base. Starting at 100: a 50% decrease gives 50; then 50% of 50 = 25, so the result is 75, not 100. Percentage changes are multiplicative, not additive — this is why "half off then half back on" leaves you 25% down.
Use Mode A. Enter the tip percentage (e.g. 18) and the bill amount. Result = (18 / 100) × bill. For a $85 dinner: 0.18 × $85 = $15.30 tip, making the total $100.30. The preset buttons handle 15%, 20%, and other common rates instantly.
Use Mode B to express your score as a percentage: 72 correct out of 90 = 80%. To find the minimum correct answers for a 70% pass on 90 questions, use Mode A: 70% of 90 = 63 answers required.
Percentage change = ((New Value − Old Value) / |Old Value|) × 100. A positive result is an increase; a negative result is a decrease. Mode C performs this automatically and displays the direction with a colour-coded arrow indicator.
Yes. Enter the old exchange rate as the "from" value and the new rate as the "to" value in Mode C. The result shows the percentage appreciation or depreciation of one currency against another — useful for tracking currency movements over time.
Percentage error = (|Experimental − Theoretical| / |Theoretical|) × 100. Use Mode C, entering the theoretical value as "from" and the experimental value as "to". The absolute result (ignore the sign) is your percentage error.
Related Tools
Percentages underpin almost every financial and analytical calculation you will encounter — from reading a payslip to evaluating a marketing campaign or comparing interest rates. Toolaroid's percentage calculator covers all four fundamental percentage operations in a single, distraction-free tool. No account required, no data sent to a server — every calculation runs entirely in your browser, so your numbers stay private.