Calculate what percent of a number is, find percentage of a total, or reverse-calculate the base value. Instant results for students and professionals.
25
200
A% of B
50
A is what % of B
12.50%
B is what % of A
800.00%
B% of what = A?
12.5
What is a Percentage?
A Percentage Calculator instantly computes four related percentage operations between any two numbers, covering every common percentage question in a single view. Rather than choosing which formula to apply, you enter Value A and Value B once — and the calculator simultaneously shows you A% of B, what percentage A is of B, what percentage B is of A, and the base number when A equals B% of it.
Percentages express a ratio on a common scale of 100, making them the universal language of comparisons: exam scores, GST rates, FD interest, discount offers, income tax slabs, profit margins, and market share statistics all use this format. The word comes from the Latin per centum — "per hundred" — and the concept is anchored in Class 5 CBSE/ICSE textbooks before appearing in virtually every domain of adult life.
The challenge with percentages is that the same two numbers give different meaningful answers depending on which direction you ask the question. "25% of 200" (the answer is 50) is a different calculation from "25 is what percent of 200" (12.5%) and "200 is what percent of 25" (800%). All three results are useful in different contexts — and all three are visible the moment you enter your numbers.
The fourth output — "B% of what = A?" — solves the reverse percentage problem: given a result and a percentage, find the original base. This is the formula behind reverse-calculating MRP from a discounted price, or finding the gross salary from TDS and tax rate. It is algebraically simple (A × 100 ÷ B) but easy to confuse with the other three operations.
Understanding percentage relationships between numbers is foundational for the Percentage Change Calculator, which uses these same operations to express how much one value has shifted relative to another over time.
How to use this Percentage calculator
Enter Value A — the number that plays the role of percentage, numerator, or result depending on which question you are asking. For "X% of a number", A is the percentage rate (e.g., 25). For "A is what % of B", A is the actual count or amount.
Enter Value B — the base or reference number. For "X% of a number", B is the base (e.g., 200). For "A is what % of B", B is the total or benchmark.
Read all four outputs at once — the results update live as you type. The highlighted primary result is A% of B (the most common query). The three secondary results give you the same pair of numbers viewed from every other angle.
Use the step breakdown — click "How was this calculated?" to see the working for each of the four formulas. This is useful for homework verification and for explaining the calculation to a client or colleague.
Interpret the fourth output carefully — "B% of what = A?" is the reverse formula. If B is 0, the output is 0 (undefined mathematically). For meaningful results, both A and B should be non-zero positive numbers.
Formula & Methodology
The calculator applies four percentage formulas simultaneously:
Formula 1 — A% of B:
Result = (A ÷ 100) × B
Formula 2 — A is what % of B:
Result = (A ÷ B) × 100
Formula 3 — B is what % of A:
Result = (B ÷ A) × 100
Formula 4 — B% of what = A (reverse percentage):
Result = (A × 100) ÷ B
Variables:
- A = Value A (the percentage rate in Formula 1; the part/numerator in Formulas 2 and 3; the known result in Formula 4)
- B = Value B (the base in Formula 1; the whole/denominator in Formula 2; part in Formula 3; the percentage rate in Formula 4)
Worked example — A = 15, B = 60:
Formula 1: (15 ÷ 100) × 60 = 9 → 15% of 60 is 9Formula 2: (15 ÷ 60) × 100 = 25% → 15 is 25% of 60Formula 3: (60 ÷ 15) × 100 = 400% → 60 is 400% of 15Formula 4: (15 × 100) ÷ 60 = 25 → 60% of 25 = 15
Precision: All outputs are rounded to 4 decimal places. For exact integer results (e.g., 25% of 200 = 50.0000), the trailing zeros are dropped by the display layer.
Edge cases:
- If B = 0, Formulas 2 and 4 return 0 (division by zero protected)
- If A = 0, Formula 3 returns 0 (division by zero protected)
- Negative inputs are accepted — percentage relationships between negative numbers are valid in contexts like temperature change or negative returns
Frequently Asked Questions
What is a percentage and how is it calculated?
A percentage is a way of expressing a number as a fraction of 100 — the word itself comes from the Latin *per centum*, meaning 'per hundred'. To calculate a percentage, divide the part by the whole and multiply by 100: if 30 students out of 120 scored above 90%, the percentage is (30 ÷ 120) × 100 = 25%. Percentages are used universally in finance, exams, discounts, tax, and statistics because they create a common scale that makes comparisons easy regardless of the original quantities.
What is the formula for calculating X% of a number?
To find X% of a number Y, use the formula: Result = (X ÷ 100) × Y. For example, 15% of ₹6,000 = (15 ÷ 100) × 6,000 = ₹900. This is the most common percentage operation — used for calculating GST on a purchase, interest on a fixed deposit, discount on a sale price, or commission on a sale. Many mental math shortcuts exist: 10% is simply dividing by 10, so 15% = 10% + 5% = 600 + 300 = ₹900.
How do I find what percentage one number is of another?
To find what percentage A is of B, use: Percentage = (A ÷ B) × 100. If you scored 78 out of 120 in an exam, your percentage is (78 ÷ 120) × 100 = 65%. This operation answers the question 'A is how many percent of B?' and is useful for calculating exam scores, market share, utilisation rates, and proportion of income spent on a category. Enter the numbers in Value A (numerator) and Value B (denominator) to get this result instantly.
What is the reverse percentage formula? (B% of what = A?)
The reverse percentage formula finds the original base value when a percentage and its result are known: Base = A × 100 ÷ B. If 20% of some number equals 50, then the original number is 50 × 100 ÷ 20 = 250. This is used when you know a discounted price and the discount percentage and want the MRP, or when you know the TDS deducted and want the gross payment. The formula is also written as: Base = A ÷ (B ÷ 100).
What is the difference between percentage and percentage points?
A percentage point is the arithmetic difference between two percentages, while percentage change expresses that difference as a proportion of the starting value. If the repo rate rises from 6% to 6.5%, it has increased by 0.5 percentage points — but the percentage change is (0.5 ÷ 6) × 100 = 8.33%. Confusing the two is a common error in financial news: 'inflation fell 2 percentage points' (from 7% to 5%) is very different from 'inflation fell 2%' (which would mean it fell from 7% to 6.86%).
What is the difference between percentage and ratio?
A ratio expresses the relative size of two quantities as A:B (e.g., 3:4), while a percentage always relates a quantity to a base of 100. A ratio of 3:4 means A is 75% of B (A ÷ B × 100), and A is 42.86% of the total (A ÷ (A+B) × 100). Percentages are easier for quick comparisons across different bases, while ratios are better for expressing proportional relationships. Use the [Ratio Calculator](/ratio-calculator/) to convert any A:B ratio into percentages and scale it to a total.
Can a percentage be more than 100%?
Yes — a percentage can exceed 100% whenever the part being measured is larger than the reference whole. If a company's debt is ₹12 lakh against equity of ₹8 lakh, its debt-to-equity ratio expressed as a percentage is 150%. Similarly, if your investment grew from ₹50,000 to ₹1,50,000, the return is (1,00,000 ÷ 50,000) × 100 = 200%. Percentages above 100% are common in finance (growth rates, leverage ratios) and engineering (efficiency metrics beyond baseline).
How is percentage used in calculating discounts in retail?
A discount percentage reduces the MRP by a specified fraction: Discount Amount = MRP × Discount% ÷ 100; Final Price = MRP − Discount Amount. A ₹2,500 shirt with 30% off costs ₹2,500 − ₹750 = ₹1,750. In India, MRP is the ceiling price inclusive of all taxes — so a 30% discount on MRP means a genuine reduction on the highest legal price. The [Discount Calculator](/discount-calculator/) handles this instantly, including the 'you pay per ₹100 MRP' metric that lets you compare deals across price points.
How do I convert a percentage to a decimal and vice versa?
To convert a percentage to a decimal, divide by 100: 25% = 0.25; 7.5% = 0.075. To convert a decimal to a percentage, multiply by 100: 0.375 = 37.5%. This conversion is important when working with formulas — compound interest, EMI, and GST calculations all use decimal rates internally. For example, GST at 18% is applied as 0.18 in the formula: GST Amount = Price × 0.18.
How is percentage used in income tax calculations in India?
Income tax in India is calculated using slab rates expressed as percentages: for the new tax regime in FY 2025-26, income between ₹3 lakh and ₹7 lakh is taxed at 5%, ₹7–10 lakh at 10%, ₹10–12 lakh at 15%, and ₹12–15 lakh at 20%, with 30% above ₹15 lakh. Each slab's tax is the applicable percentage of only the income within that band, not of total income. The marginal rate (the rate on the last rupee earned) determines the tax benefit of any deduction — so a ₹50,000 deduction saves ₹15,000 in tax if you are in the 30% slab.
What is the percentage formula used in CBSE/ICSE Class 5–10 mathematics?
In Indian school mathematics, three core percentage formulas are taught: (1) Percentage = (Part ÷ Whole) × 100, (2) Part = (Percentage ÷ 100) × Whole, and (3) Whole = Part × 100 ÷ Percentage. These three formulas are exactly what the four outputs on this calculator compute — making it a direct tool for checking CBSE/ICSE homework and exam preparation. Problems involving profit and loss, simple interest, and discount all reduce to these three operations.
How do I calculate percentage marks in board exams in India?
To calculate your percentage in a board exam, divide your total marks obtained by the total maximum marks and multiply by 100: Percentage = (Marks Obtained ÷ Total Marks) × 100. For example, 436 out of 500 in Class 10 CBSE = 87.2%. For Class 12 CBSE, the percentage is calculated on the best-of-five subjects if you have more than five. Most Indian colleges use this percentage for cutoff eligibility, and a few (like DU) use a best-of-four formula — always check the specific institution's rule.