Percentage Calculator: Find Percentages, Changes and Discounts

The most frequent percentage calculation in daily life is determining what a specific percentage of an amount equals. Whether you are finding the sales tax on a retail purchase, calculating a server tip at a restaurant, working out a sales commission, or computing a promotional discount, this calculation finds the portion represented by a given rate.

The standard mathematical formula for finding a percentage of a number is:

Percentage of a Number = (Percentage ÷ 100) × Total

For example, to calculate 15% of 200, divide 15 by 100 to get the decimal 0.15, and multiply by 200. The result is exactly 30 (0.15 × 200 = 30). In a practical shopping or dining context, if your bill is $200 and you wish to leave a 15% gratuity, your tip amount is $30, bringing the total payment to $230.

• Discounts: If an item costs $80 with a 25% discount, 25% of $80 is $20 savings, making the final sale price $60.
• Sales Tax: If your taxable cart total is $120 and local sales tax is 8%, the tax due is 0.08 × 120 = $9.60 (this tool calculates general percentages and does not provide specialized tax advice).
• Commissions: A 5% broker commission on a $10,000 transaction equals (5 ÷ 100) × 10,000 = $500.
• Quick Tip: You can click our preset chips (5%, 10%, 15%, 20%, 25%, 50%) above to fill this mode with standard percentages in a single tap.

Mode 2 computes directional percentage change between an original baseline value and a new value. This calculation is indispensable for tracking personal salary adjustments, monitoring corporate revenue growth, measuring product inflation, and comparing before-and-after metrics in scientific experiments.

The mathematical formula for percentage change is:

Percentage Change = ((New Value − Original Value) ÷ Original Value) × 100

The direction of the result indicates whether the change is an increase or a decrease: if the new value is greater than the original value, the percentage is positive (+); if the new value is smaller, the percentage is negative (−).

• Percentage Increase Example: If your hourly wage rises from $100 to $150, the change is ((150 − 100) ÷ 100) × 100 = (50 ÷ 100) × 100 = +50.00% increase.
• Percentage Decrease Example: If an item's price is marked down from $200 to $150, the change is ((150 − 200) ÷ 200) × 100 = (−50 ÷ 200) × 100 = −25.00% decrease.
• Baseline Principle: Percentage change always measures growth or decline relative to the original value as the baseline denominator. Notice that moving from 100 up to 150 is a +50% increase, but moving from 150 back down to 100 is a −33.33% decrease because the starting baseline changes.
• Mathematical Edge Case: If the original value is zero (0), the conventional formula requires dividing by zero, which is mathematically undefined. Our calculator explicitly alerts you that percentage change from zero is undefined rather than presenting misleading 0% or infinite figures.

Mode 3 answers the question: 'X is what percentage of Y?' This ratio calculation determines what proportion a part represents of an entire whole, standardized to a base of 100.

The algebraic formula for this ratio is:

Percentage = (Part ÷ Total) × 100

For example, if you score 45 correct answers on an examination containing 150 total questions, divide 45 by 150 to get 0.30, then multiply by 100. The result is 30% (45 ÷ 150 = 0.30 = 30%).

• Test Scores & Grades: Score 76 points out of 80 total points? (76 ÷ 80) × 100 = 95.00% (an 'A' grade).
• Household Budgeting: If your monthly income is $4,000 and rent is $1,200, rent consumes (1,200 ÷ 4,000) × 100 = 30.00% of your total budget.
• Survey Statistics: If 350 out of 500 respondents favor a proposal, that represents (350 ÷ 500) × 100 = 70.00% approval.
• Goal & Fitness Tracking: If your daily target is 10,000 steps and you have walked 6,500 steps, you have achieved (6,500 ÷ 10,000) × 100 = 65.00% of your daily goal.
• Zero Denominator Edge Case: If the total (Y) is 0, the ratio is mathematically undefined because a whole cannot consist of zero parts.

Calculating percentages online with GetFunTools is fast, intuitive, and accurate. Follow these simple steps to solve any percent problem in seconds:

• 1. Choose the Calculation Mode: Click on one of the three mode tabs at the top of the calculator. Choose 'What is X% of Y' to find an amount, '% Change' to evaluate growth or decline between two values, or 'X is what % of Y' to find a ratio.
• 2. Enter Your Numeric Values: Type your numbers into the designated input fields. In Mode 1, you can also click any of the preset percentage chips (5%, 10%, 15%, 20%, 25%, 50%) to fill in common rates instantly.
• 3. Read the Instant Result: The calculated percentage or monetary amount displays immediately in the prominent summary card with two decimal places of precision.
• 4. Review the Formula Breakdown: Check the step-by-step arithmetic notation and explanatory sentence beneath the result card to verify the mathematical working.
• 5. Copy or Reset: Click 'Copy Result' to paste your answer into another document, or click 'Reset' to return inputs to their defaults.

Here is a reference set of verified mathematical examples covering all four fundamental percentage problem types:

• Example 1 — Finding 20% of 150: Formula: (20 ÷ 100) × 150 = 0.20 × 150 = 30.00. Result: 20% of 150 is 30.
• Example 2 — Increasing 80 to 100: Formula: ((100 − 80) ÷ 80) × 100 = (20 ÷ 80) × 100 = 0.25 × 100 = +25.00%. Result: Moving from 80 to 100 is an increase of 25%.
• Example 3 — Decreasing 200 to 150: Formula: ((150 − 200) ÷ 200) × 100 = (−50 ÷ 200) × 100 = −0.25 × 100 = −25.00%. Result: Moving from 200 to 150 is a decrease of 25%.
• Example 4 — Finding what percentage 30 is of 120: Formula: (30 ÷ 120) × 100 = 0.25 × 100 = 25.00%. Result: 30 is 25% of 120.

Many people confuse 'percentage change' with 'percentage difference', but in mathematics, statistics, and financial modeling, they serve two fundamentally distinct purposes.

Percentage Change is directional and requires an original starting baseline. It compares an 'Old' value with a 'New' value using the formula ((New − Old) ÷ Old) × 100. Because it measures how an initial state changed over time, the order of numbers matters: increasing from 100 to 150 is a +50% change, while decreasing from 150 to 100 is a −33.33% change. Mode 2 on this calculator computes Percentage Change.

Percentage Difference, by contrast, is non-directional. It compares two numbers when neither number is the 'original' or 'baseline' value (for example, comparing the heights of two adults or the populations of two cities). The formula divides the absolute difference by the average of the two numbers:

Percentage Difference = (|Value A − Value B| ÷ ((Value A + Value B) ÷ 2)) × 100

For example, the percentage difference between 100 and 150 is (|100 − 150| ÷ ((100 + 150) ÷ 2)) × 100 = (50 ÷ 125) × 100 = 40.00%. Notice that reversing 100 and 150 yields the exact same 40% because neither value is considered the baseline.

• Use Percentage Change when you have a before-and-after relationship (e.g., historical prices, revenue growth, test retakes).
• Use Percentage Difference when you are comparing two independent parallel items (e.g., product A vs. product B).
• Important: Mode 2 of this calculator specifically computes Percentage Change relative to your starting baseline.

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