How do I calculate what is X% of a number?

Multiply the number by X then divide by 100. For example, 20% of 150 = (20 ÷ 100) × 150 = 30. Use the Basic tab in this calculator to get instant results.

How do I find what percentage one number is of another?

Divide the part by the whole and multiply by 100. For example, 30 is what percent of 150? (30 ÷ 150) × 100 = 20%. Use the What % tab.

How do I calculate percentage change?

Subtract the original value from the new value, divide by the absolute original value, then multiply by 100. Formula: ((New − Old) ÷ |Old|) × 100. A positive result is an increase; negative is a decrease.

What is a reverse percentage calculation?

A reverse percentage finds the original whole when you know a part and the percentage it represents. Formula: Whole = Part ÷ (Percentage ÷ 100). For example, 30 is 20% of what number? 30 ÷ 0.20 = 150.

How do I increase a number by a percentage?

Multiply the number by (1 + percentage/100). For example, 200 increased by 15% = 200 × 1.15 = 230. Use the Add/Subtract tab for both increase and decrease in one step.

How do I decrease a number by a percentage?

Multiply the number by (1 − percentage/100). For example, 200 decreased by 15% = 200 × 0.85 = 170.

Is this calculator accurate for financial calculations?

Yes for general use. Results are computed using standard floating-point arithmetic and displayed to up to 8 significant decimal places. For high-stakes financial decisions always verify with a certified financial tool.

Can I see my past calculations?

Yes. Every calculation is automatically saved in the History panel at the bottom of the tool. You can clear the history at any time.

What is the difference between percentage points and percent change?

Percentage points are the arithmetic difference between two percentages (e.g., 30% − 20% = 10 percentage points). Percent change is relative: a change from 20% to 30% is a 50% increase (10 ÷ 20 × 100).

Does this tool store my calculations?

No data is sent to any server. All calculations run in your browser using JavaScript. History is stored in memory only and cleared when you refresh the page.

Percentage Calculator — Free Online % Tool

What is X% of Y?

Find a percentage of any number. Great for tips, discounts, taxes, and scores.

result = (X ÷ 100) × Y

Percentage (X)

% of

Number (Y)

X is what percent of Y?

Find what percentage one number is of another. Perfect for grades, ratios, and market share.

result = (X ÷ Y) × 100

Number (X)

is what % of

Number (Y)

Percentage Change

Calculate the percentage increase or decrease between two values. Essential for sales growth, price changes, and statistics.

result = ((New − Old) ÷ |Old|) × 100

Original value

→

New value

X is Y% of what number?

Work backwards from a known part and percentage to find the original whole. Useful for finding original prices before a discount.

result = X ÷ (Y ÷ 100)

The part (X)

Percentage (Y%)

Add or Subtract a Percentage

Increase or decrease a number by a percentage in one step. Ideal for applying VAT, discounts, commissions, or markups.

add: Y × (1 + X/100) | sub: Y × (1 − X/100)

Base number (Y)

Percentage (X%)

Calculation History

Your All-in-One Percentage Calculator

This tool puts five of the most common percentage calculations on one page so you never have to remember a formula or open a spreadsheet. Every calculation runs instantly in your browser — nothing is sent to a server.

The five modes

Basic % — "What is 20% of 150?" → 30. Use for tips, discounts, and tax amounts.
What %? — "30 is what percent of 150?" → 20%. Use for grades, ratios, and market share.
% Change — "What is the % change from 80 to 100?" → +25%. Use for growth rates and price movements.
Reverse % — "30 is 20% of what?" → 150. Use to find original prices after discounts.
Add / Subtract — "200 plus 15%" → 230 and "200 minus 15%" → 170. Use for VAT, markups, and commissions.

Every result is logged in the Calculation History panel so you can track your work without switching tabs or opening a notepad.

How to Use the Percentage Calculator

Pick a mode

Click the tab that matches your question — Basic %, What %, % Change, Reverse %, or Add/Subtract.

Enter your numbers

Fill in the input fields. Labels tell you exactly what each field expects.

Calculate

Click Calculate or press Enter. The result appears instantly with a plain-English explanation.

Copy or review

Copy the result to your clipboard, or scroll down to see all recent calculations in History.

Percentage Formulas Reference

Mode	Formula	Example
Basic %	`(X ÷ 100) × Y`	20% of 150 = 30
What %?	`(X ÷ Y) × 100`	30 ÷ 150 × 100 = 20%
% Change	`((New − Old) ÷ \|Old\|) × 100`	(100−80)÷80×100 = +25%
Reverse %	`X ÷ (Y ÷ 100)`	30 ÷ 0.20 = 150
Add %	`Y × (1 + X ÷ 100)`	200 × 1.15 = 230
Subtract %	`Y × (1 − X ÷ 100)`	200 × 0.85 = 170

Important distinctions

Percent vs percentage points — going from 20% to 30% is 10 percentage points but a 50% increase.
Absolute vs relative change — % Change uses the absolute value of the original for the denominator, so negative-to-positive changes are handled correctly.
Reverse % vs basic % — if you already know the part and the percentage, use Reverse % to find the whole; if you know the whole and the percentage, use Basic %.

Real-World Use Cases

Shopping & Finance

Calculate a sale discount — "What is 30% off $89.99?" (Basic %)
Find the original price — "A $63 item is 30% off — what was the original price?" (Reverse %)
Add sales tax or VAT — "What is $120 plus 8% tax?" (Add/Subtract)
Calculate a tip — "What is 18% of $47.50?" (Basic %)

Business & Analytics

Track revenue growth — "Revenue went from $45k to $58k — what's the growth rate?" (% Change)
Calculate profit margin — "Profit is $12k on revenue of $80k — what's the margin?" (What %)
Apply a commission — "Add 7.5% commission to a $2,500 sale" (Add/Subtract)
Measure conversion rate — "450 conversions from 3,200 visitors — what is the rate?" (What %)

Education & Science

Calculate a test score — "42 correct out of 55 — what percentage?" (What %)
Find a percentage error — "Measured 98, expected 100 — what is the error?" (% Change)
Determine a concentration — "What is 3% of 500ml?" (Basic %)

Percentage Calculator