Percentage Calculator
Calculate percentages, what-percent relationships, increases, decreases, and percent change.
How to use this percentage calculator
- Choose the type of percentage calculation you need
Select from percent of a value, what percent is A of B, percent change, increase by percent, or decrease by percent.
- Enter the numbers in the input fields
Type the values in the first and second value fields.
- Read the result instantly
The result appears in the result panel along with an explanation.
- Try the reverse calculation to double-check
Work backwards to verify the answer is correct.
How this percentage calculator works
This percentage calculator handles five common percentage operations in one tool: finding a percent of a value, finding what percent one number is of another, computing percent change between two numbers, increasing a value by a given percent, and decreasing a value by a given percent. Each mode applies straightforward arithmetic that mirrors the way percentages are taught in school and used daily in finance, retail, science, and data analysis. The calculator converts percentages to decimal form internally when needed, performs the multiplication or division, and returns both the final result and a plain-language explanation so you can verify the logic or reproduce it in a spreadsheet.
Percent of value: result = value × (percent ÷ 100)
What percent is A of B: percent = (A ÷ B) × 100
Percent change: change = ((new − old) ÷ old) × 100
Increase by percent: result = value × (1 + percent ÷ 100)
Decrease by percent: result = value × (1 − percent ÷ 100) To find what 15% of 240 is: result = 240 × (15 ÷ 100) = 36. To find what percent 45 is of 180: percent = (45 ÷ 180) × 100 = 25%. To compute the percent change from 200 to 250: change = ((250 − 200) ÷ 200) × 100 = 25%. To increase 80 by 12%: result = 80 × 1.12 = 89.60. To decrease 500 by 30%: result = 500 × 0.70 = 350.
A shop raises the price of an item from 80 to 92. The percentage increase is ((92 − 80) ÷ 80) × 100 = 15%. Use the percent-change mode with 80 as the old value and 92 as the new value to confirm the result instantly.
A student needs to find 35% of 260. Using the percent-of-a-value mode: 260 × (35 ÷ 100) = 91. This kind of calculation appears in tip splitting, discount shopping, and exam-score analysis.
- ✓ Percentages are entered as whole numbers (e.g. 25 means 25%) and converted to decimal form internally by dividing by 100.
- ✓ Percent-change mode treats the first value as the old baseline and the second as the new value; swapping them reverses the sign.
- ✓ Percent-change mode requires a non-zero baseline, and what-percent mode requires a non-zero whole.
- ✓ The calculator uses simple percentage arithmetic — it does not compound, annualize, or apply logarithmic scaling.
- ✓ Results are rounded to two decimal places for display; internal calculations retain full floating-point precision.
- A positive percent change means the value increased; a negative result means it decreased — the sign carries the direction automatically.
- Successive percentage changes do not add linearly: a 20% increase followed by a 20% decrease does not return you to the original value (it leaves you 4% lower).
- For tax-inclusive or tax-exclusive price calculations, use percent-increase mode with the tax rate to get the gross amount, or reverse the math manually to recover the original value.
- In spreadsheet formulas the same logic applies: =A1*(B1/100) for percent-of, =A1/B1*100 for what-percent mode, and =(B2-A2)/A2*100 for percent change.
- National Council of Teachers of Mathematics — Principles and Standards for School Mathematics (percentage operations)
- Khan Academy — Percentages module (arithmetic foundations)
What is a percentage?
A percentage is a way of expressing a number as a fraction of 100. The word itself comes from the Latin per centum, meaning by the hundred. When you say 45%, you mean 45 parts out of every 100, which is equivalent to the decimal 0.45 or the fraction 45/100. Percentages are everywhere in daily life: sales tax rates, exam scores, battery levels, interest rates, nutritional labels, and polling data all rely on the percentage format because it provides an intuitive common denominator that makes comparisons easy. Converting between percentages, decimals, and fractions is straightforward — divide by 100 to go from a percentage to a decimal, and multiply by 100 to go the other way. Understanding this simple relationship is the foundation for every percentage operation, whether you are calculating a tip, analysing year-over-year revenue growth, or determining how much of a recipe to scale.
Percentage vs percentage points
One of the most common sources of confusion in everyday statistics is the difference between a percentage change and a change measured in percentage points. Suppose an interest rate rises from 3% to 5%. The absolute difference is 2 percentage points, but the relative increase is ((5 − 3) ÷ 3) × 100 ≈ 66.7%. Both statements are technically correct, but they communicate very different magnitudes. Journalists, politicians, and marketers sometimes blur the distinction, which can make a change sound larger or smaller than it really is depending on which framing they choose. As a rule of thumb, percentage points describe the raw arithmetic gap between two percentages, while percent (or percent change) describes how large that gap is relative to the starting value. This calculator computes relative percent change in its percent-change mode. If you need the absolute difference in percentage points, simply subtract the two percentage figures directly without dividing by the base.
Percentage calculator FAQs
How do I calculate what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 45 out of 180 is (45 ÷ 180) × 100 = 25%. In this calculator, use the dedicated 'What percent is A of B?' mode.
Why does a 50% increase followed by a 50% decrease not return the original value?
Because each percentage is applied to a different base. A 50% increase on 100 gives 150, but a 50% decrease on 150 subtracts 75, leaving 75 — not 100. Percentages compound relative to their current base, not the original.
Can I use this for discount and sales-tax calculations?
Yes. Use the decrease-by-percent mode to apply a discount, or the increase-by-percent mode to add sales tax. For example, a 20% discount on an item priced at 85 gives 85 × (1 − 0.20) = 68.
What is the difference between percentage points and percent?
Percentage points measure the absolute difference between two percentages (e.g. 30% to 35% is 5 percentage points), while percent measures the relative change (that same move is a 16.67% increase). This calculator computes relative percent change.
How do I reverse a percentage to find the original number?
If you know the result after an increase, divide by (1 + rate). For example, if a price after 8% tax is 54, the pre-tax price is 54 ÷ 1.08 = 50. For a decrease, divide by (1 − rate).