The fastest free online percentage calculator. Solve any % problem in one click — no ads blocking your results, no login required.
Find the percentage of any number. Example: "What is 25% of 200?"
Find what percentage one number is of another. Example: "50 is what % of 200?"
Find the % change from one value to another. Works for both increase and decrease.
Add or subtract a percentage from any number. Example: "Increase 500 by 15%".
Pick the right calculator for your specific percentage problem
Calculate the % increase between two numbers. Ideal for salary raises, price increases, and growth tracking.
Find the % drop from one value to another. Perfect for discounts, price reductions, and loss calculations.
Calculate any percentage change (positive or negative) between an old and new value. Great for finance, stats, and reports.
Compare two values symmetrically with no reference point. Used in science, data analysis, and research comparisons.
Find the accuracy of an experimental vs theoretical value. Essential for chemistry, physics, and lab experiments.
Quickly find the sale price after applying any percentage discount. Perfect for shopping, retail pricing, and deals.
Learn the definition, formula, and real-world uses of percentages. Beginner-friendly guide with worked examples.
All percentage formulas in one place — basic %, increase, decrease, change, difference, and error formulas explained.
A percentage is a number expressed as a fraction of 100. The word comes from the Latin per centum, meaning "by the hundred." Percentages are used everywhere — from calculating a tip at a restaurant to tracking stock market returns, exam scores, and tax rates. Understanding how to calculate a percentage is one of the most practical math skills you can have.
Our free percentage calculator handles all standard percentage problems instantly, but knowing the formulas yourself helps you verify results and understand what each number means.
Percentage (%) = (Part ÷ Whole) × 100
Use this formula when you want to express one number as a percentage of another. If a student scores 72 out of 90 marks, their percentage score is (72 ÷ 90) × 100 = 80%.
Question: What percentage is 45 out of 180?
Step 1: Divide the part by the whole → 45 ÷ 180 = 0.25
Step 2: Multiply by 100 → 0.25 × 100 = 25%
Result = (Percentage ÷ 100) × Number
This is the most common percentage question: "What is X% of Y?" To find 30% of 250, calculate (30 ÷ 100) × 250 = 75. Use our calculator above for instant answers — just enter the percentage and the number in Tab 1.
When a value grows from an old number to a new number, you're looking at a percentage increase. If a product price rises from $40 to $52, the percentage increase is ((52 − 40) ÷ 40) × 100 = 30%. Conversely, a percentage decrease applies when the new value is lower than the old value.
% Increase = ((New Value − Old Value) ÷ Old Value) × 100
% Decrease = ((Old Value − New Value) ÷ Old Value) × 100
Percentage change always has a reference (the starting/old value), and can be positive (increase) or negative (decrease). Percentage difference, on the other hand, compares two values without a defined starting point — it uses the average of both values as the base. Use percentage change for before-and-after comparisons, and percentage difference when comparing two independent measurements.
To calculate a discount, multiply the original price by the percentage discount divided by 100, then subtract that from the original price. For example, 25% off $120 = $120 − ($120 × 0.25) = $90. Our percent off calculator makes this instant for any price and discount percentage.
Sale Price = Original Price × (1 − Discount% ÷ 100)
Percent error measures how close an experimental or measured value is to a known theoretical (accepted) value. It is widely used in chemistry, physics, and engineering labs. The formula uses the absolute difference between the experimental and theoretical values, divided by the theoretical value, multiplied by 100. A lower percent error indicates higher accuracy.
% Error = (|Experimental − Theoretical| ÷ |Theoretical|) × 100
Percentages appear in almost every area of everyday life. In finance, interest rates, investment returns, and tax rates are all expressed as percentages. In retail, discount labels ("25% off") and sales tax are calculated using percentage formulas. In education, exam scores and grade cutoffs use percentages. In health, body fat percentage, blood oxygen saturation (SpO₂), and nutritional information on food labels all rely on percentage calculations. Understanding how to calculate percentages fluently — or using a reliable percentage calculator — saves time and avoids costly mistakes.
According to Math Is Fun, percentages are one of the most universally applied mathematical concepts across both academic and professional settings. External resources like Khan Academy's percentage lessons offer further depth if you want to strengthen your understanding of the underlying concepts.
Quick answers to the most common percentage questions
Divide the part by the whole, then multiply by 100. Formula: % = (Part ÷ Whole) × 100. For example, 25 out of 200 = (25 ÷ 200) × 100 = 12.5%. You can also use the calculator on this page for instant results.
There are several percentage formulas: Basic: % = (Part ÷ Whole) × 100. Find % of a number: Result = (% ÷ 100) × Number. % Increase: ((New − Old) ÷ Old) × 100. % Decrease: ((Old − New) ÷ Old) × 100. See our full percentage formula guide for all variations.
Subtract the old value from the new value, divide by the old value, then multiply by 100. Example: from 80 to 100 → ((100 − 80) ÷ 80) × 100 = 25% increase. Use our dedicated percentage increase calculator for instant results.
Formula: % Decrease = ((Old Value − New Value) ÷ Old Value) × 100. Example: a price drops from $80 to $60 → ((80 − 60) ÷ 80) × 100 = 25% decrease. Try the percentage decrease calculator for fast answers.
Percentage change measures how much a value has changed relative to its original value — it has a clear starting point. Percentage difference compares two values without a defined reference, using the average of both as the base. Use change for before/after, and difference for comparing two independent values.
Multiply the original price by the discount percentage, then subtract: Sale Price = Original Price × (1 − Discount% ÷ 100). Example: 20% off $150 = $150 × 0.80 = $120. Use our percent off calculator for any price and discount instantly.
Percent error measures the accuracy of an experimental result compared to a known/theoretical value. Formula: % Error = (|Experimental − Theoretical| ÷ |Theoretical|) × 100. It is commonly used in chemistry and physics labs. Try our percent error calculator for quick lab calculations.
Formula: Result = (Percentage ÷ 100) × Number. To find 15% of 320: (15 ÷ 100) × 320 = 48. Use Tab 1 of the calculator on this page — enter 15 in the percentage field and 320 in the number field, then click Calculate.