Percentage Calculator

What is a Percentage Calculator?

A percentage calculator solves the four most common percentage problems in everyday life: finding a percentage of a number (for tips, discounts, and taxes), finding what percentage one number is of another (for scores and ratios), calculating percentage change (for price changes and growth rates), and increasing or decreasing a value by a percentage (for salary hikes and markdowns).

How to Use This Calculator

Select the calculation type using the four tabs, enter your numbers, and the result updates instantly:

• Tab 1 — "What is X% of Y?" Enter the percentage and the base number. Use this for tips (15% of $45), discounts, and taxes.
• Tab 2 — "X is what % of Y?" Enter both numbers. Use this for test scores (42 out of 50), market share, and completion rates.
• Tab 3 — "% Change" Enter the old and new values. Positive result = increase; negative = decrease. Use for price changes and growth rates.
• Tab 4 — "Increase/Decrease by %" Enter the original value and percentage. Shows both increase and decrease results simultaneously.

Formulas Used

Common Uses of Percentage Calculations

• Tips: Calculate 18% or 20% of a restaurant bill
• Discounts: Find the sale price after 30% off
• Taxes: Add 8.5% sales tax to a purchase
• Grades: Convert raw scores to percentages
• Finance: Calculate investment returns, interest, and portfolio allocation
• Salary: Calculate a 5% raise on current salary
• Statistics: Express survey results and market share as percentages

Frequently Asked Questions

How do you calculate what percent of a number is?

Multiply the number by the percentage divided by 100. Example: 15% of 200 = 200 × 0.15 = 30. Used for tips, discounts, and tax calculations.

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

Divide the first number by the second and multiply by 100. Example: 45 ÷ 180 × 100 = 25%. Used for test scores, market share, and completion rates.

How do you calculate percentage change?

Percentage change = ((New − Old) ÷ |Old|) × 100. Positive = increase; negative = decrease. Example: from $80 to $100 = +25%. From $150 to $120 = −20%.

How do you increase or decrease a number by a percentage?

Increase: multiply by (1 + rate). Decrease: multiply by (1 − rate). Example: $250 × 1.20 = $300 (+20%); $250 × 0.80 = $200 (−20%).

What is the difference between percentage points and percent?

Percentage points are the arithmetic difference between two percentages (5% to 8% = 3 percentage points). Percent is the relative change ((8−5)/5 × 100 = 60%). These mean very different things — confusing them is a common media error.

How do you calculate a tip percentage?

Tip = Bill × (Tip% ÷ 100). Example: 18% on $65 → $65 × 0.18 = $11.70. Total = $76.70. Common tips: 15% (standard), 18% (good), 20% (great).

How do you calculate a discount?

Sale price = Original × (1 − Discount% ÷ 100). Example: 30% off $120 → $120 × 0.70 = $84 (saving $36). Note: stacked discounts are multiplied, not added.

What is compound percentage growth?

Compound growth = Initial × (1 + rate)^periods. Example: $1,000 at 7%/year for 10 years = $1,967. This differs from simple percentage which adds the same flat amount each period.