Percentage Calculator

About this percentage calculator

A percentage calculator turns everyday proportion questions into clear answers. Whether you need “what is 18% of 2,450?”, “45 is what percent of 200?”, or “how much did sales grow from last year?”, this tool solves the five most common percentage problems in one place.

All math runs in your browser. Nothing you enter is uploaded or stored, so you can use it for homework, shopping discounts, exam scores, business KPIs, or tip checks with full privacy.

How to use

Choose a mode: X% of Y, reverse %, percent change, increase, or decrease.
Enter the two numbers for that mode.
Results update instantly — including the formula used.

Formula

X% of Y = (X ÷ 100) × Y

X is what % of Y = (X ÷ Y) × 100

Percent change = ((New − Old) ÷ Old) × 100

Increase by X% = Y × (1 + X/100)

Decrease by X% = Y × (1 − X/100)

Worked examples

Example 1: What is 15% of 80? → (15 ÷ 100) × 80 = 12.

Example 2: 40 is what percent of 160? → (40 ÷ 160) × 100 = 25%.

Example 3: Price rose from $50 to $65. Percent change = ((65−50)÷50)×100 = 30% increase.

Tips

Percent change and percentage points are different. A rate moving from 5% to 7% is +2 percentage points, but a 40% relative increase.
When reversing a discount, divide the sale price by (1 − discount). $70 after 30% off → 70 ÷ 0.7 = $100 original.
For stacked discounts (20% then 10%), apply them sequentially — never add 20+10.

Frequently asked questions

How do I calculate a percentage of a number?

Multiply the number by the percent divided by 100. For 20% of 150: 150 × 0.20 = 30.

How do I calculate percentage increase?

Subtract the original from the new value, divide by the original, then multiply by 100. Or use the Increase by % mode on this page.

Is this percentage calculator free?

Yes. The CalCulator percentage calculator is free to use with no signup and no limits.

Can I use it on mobile?

Yes. The page is mobile-optimized and works in any modern browser on phones and tablets.

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