Every everyday percent calculation in one place — percent of a value, percent change, percent increase or decrease, and reverse lookup.
Tap a tab — results update live as you type.
20 % of 150 is
As fraction
30 / 150
part / whole
As decimal
0.2
% ÷ 100
Complement
80 %
100 % − P
Remainder
120
N − result
| Calculation | Formula | Example |
|---|---|---|
| Percent of | P × N ÷ 100 | 20 % of 150 = 30 |
| Is what % | A ÷ B × 100 | 30 of 150 = 20 % |
| % Change | (V₂ − V₁) ÷ V₁ × 100 | 80 → 100 = +25 % |
| Increase | V × (1 + P/100) | 200 +15 % = 230 |
| Decrease | V × (1 − P/100) | 200 −15 % = 170 |
| Reverse | F ÷ (1 + P/100) | 120 after +20 % = 100 |
The Method
A percentage is a fraction expressed out of 100 — the word literally means "per hundred". The three foundational operations are: finding a percent of a number (P% × N ÷ 100), expressing one number as a percent of another (A ÷ B × 100), and measuring percent change ((new − old) ÷ |old| × 100). Every other percent calculation — discounts, markups, tips, growth rates — is just one of these three with a different label.
Working for the current input
About This Tool
A percentage calculator handles every common "what percent of…?" question in a single interface. Pick a mode at the top of the calculator — percent of, is what percent of, percent change, increase / decrease, or reverse percent — and the result updates as you type.
Percentages are everywhere in daily life: discounts and sale prices, tax and tip, interest rates, grades and test scores, opinion polls, growth and inflation rates, battery levels, nutrition labels. Each is one of just a few underlying formulas. The reference table on the calculator panel maps every mode to its formula, so you can also use this tool as a quick cheat sheet.
One subtle gotcha worth knowing: percent change and percentage points are different. Going from 4 % to 5 % is a 25 % change, but only a 1 percentage-point change. Confusing the two is the most common mistake in news headlines and election coverage. This calculator's % change mode always returns the relative change; the table on the page explains the distinction.
Use this free percentage calculator for shopping, school, salary, statistics, journalism, or any time a percent question shows up. All calculation runs in your browser — no sign-up, no tracking.
Five Modes
Percent of, is what %, percent change, increase / decrease, and reverse — all in one tool.
Visual Donut + Bar
See the proportion as both a donut chart and a progress bar — instant intuition.
Fraction + Decimal
Each result also shown as a fraction and decimal — convenient for cross-checking.
Step-by-Step Working
Substituted formula shown for every result — ready to paste into homework.
100% Free & Private
No account, no tracking — every calculation runs locally in your browser.
Negative-Aware
Handles negative starts, decreases, and percent change with a zero baseline correctly.
One calculator covers every common percent question — pick the matching mode and type in your values.
Tap one of the five tabs — percent of, is what %, % change, increase / decrease or reverse. The form below switches to the right input layout.
Each mode needs only two inputs. The labels tell you exactly what each field expects — percent, whole, part, old, new, etc.
The headline figure is the answer; the line above it tells you what was asked, and the line below shows the formula in plain text.
Each result is also shown as a fraction, a decimal, the complement, and the remainder — useful for cross-checks.
The donut and progress bar give a quick read on whether the percentage is small, large, or near 100 % at a glance.
The formula card lower on the page shows the step-by-step substitution, formatted exactly as you would write it out.
Everything you need to know about percentages, percent change, and percentage points.
Multiply the number by the percentage divided by 100. For example: 20 % of 150 = 150 × 0.20 = 30. The shortcut for common percents: 10 % is the number with the decimal moved one place left; 50 % is half; 25 % is a quarter; 1 % is the number with the decimal moved two places left.
Percent change = ((new − old) / |old|) × 100. A positive result is a percent increase, a negative result is a percent decrease. The denominator is the old value (not the new one), and you take the absolute value to make sign behaviour consistent when starting from negative numbers.
Percent change is relative; percentage points are absolute. Going from 4 % to 5 % is a 1 percentage-point change, but a 25 percent change. Mixing the two is the most common reporting error in news and politics — always clarify which one is meant.
Use the Reverse mode. If a final price is F after a P% increase, the original was F / (1 + P / 100). So if something costs 120 after a 20 % markup, the original was 120 / 1.2 = 100. The same formula works for decreases — use a negative P.
Yes. 120 % of 50 is 60 — perfectly valid. Percentages over 100 % are common in growth rates, returns, and any context where the value can exceed the reference. The "percent" symbol just means "÷ 100"; there is no upper limit.
No. Sequential percent changes do not cancel. 100 × 0.5 = 50; 50 × 1.5 = 75. You end up at 75 % of the original, a 25 % loss overall. To exactly reverse a P % decrease you need an increase of P / (100 − P) × 100 percent.
Divide the numerator by the denominator and multiply by 100. 3/4 = 0.75 = 75 %. Use the Is what % mode of this calculator: enter the numerator as the part and the denominator as the whole.
No — division by zero is undefined, and percent change is relative to the old value. When the baseline is zero, the change is reported as undefined or "—" and you should describe the change using absolute values instead. For starting values very close to zero, percent change becomes extremely volatile and is often misleading.
Markup is profit divided by cost; margin is profit divided by sale price. A 50 % markup on a $10 item gives a sale price of $15, but the margin is only $5 / $15 ≈ 33 %. Retailers usually quote margin; suppliers usually quote markup.