Percentage Calculator
Five percentage modes in one tool — find X% of a number, calculate what percent one value is of another, find percent change between two values, or calculate a new value after a percentage increase or decrease. Every result shown with full step-by-step calculation.
Choose a percentage mode
Select the question you want answered, then enter your values.
What is X% of Y? — e.g. "What is 15% of 240?" or "What is 8.9% of $800?"
What percent is X of Y? — e.g. "42 is what % of 60?" or "50 is what % of 200?"
What is the % change between two values? Auto-detects increase or decrease.
What is the value after increasing a number by a given percentage?
What is the value after decreasing a number by a given percentage?
Five modes at a glance
X% of Y → find the part value
X is what % of Y → find the ratio (%)
% Change → increase or decrease, auto-detected
% Increase / Decrease → new value after applying %
Common uses
Discounts, sales tax, tips, exam scores, salary raises, investment returns, revenue growth, depreciation, and budget comparisons.
What to do next
Want to understand the formula in depth?
Step-by-step
What this calculator does
The Percentage Calculator covers five distinct calculation types, each solving a different kind of percentage problem. Select the mode that matches your question, enter the values you know, and the calculator produces the answer instantly — with a breakdown of the arithmetic behind it.
X% of Y — finds the part. Enter a percentage and a base number to get the resulting value (e.g. 25% of 200 = 50).
X is what % of Y — finds the ratio. Enter two numbers to see what percentage the first is of the second (e.g. 50 of 200 = 25%).
% Change — finds the relative change. Enter before and after values to get the percentage increase or decrease.
% Increase / Decrease — applies a percentage to a starting value to find the new value after a known change.
Percentage formulas
Part = (Percentage ÷ 100) × Whole
e.g. 25% of 200 → (25 ÷ 100) × 200 = 50
Percentage = (Part ÷ Whole) × 100
e.g. 50 of 200 → (50 ÷ 200) × 100 = 25%
% Change = ((New − Original) ÷ Original) × 100
Positive = increase · Negative = decrease
e.g. $80 → $100 → ((100 − 80) ÷ 80) × 100 = +25%
New = Original × (1 + % ÷ 100)
e.g. $200 + 15% → 200 × 1.15 = $230
New = Original × (1 − % ÷ 100)
e.g. $200 − 15% → 200 × 0.85 = $170
Example calculations
These examples use the default preset values from each mode. Run them in the calculator above to verify.
What is 25% of 200?
= (25 ÷ 100) × 200 = 0.25 × 200 = 50
25% of 200 equals 50. The remaining 75% is 150.
50 is what percent of 200?
= (50 ÷ 200) × 100 = 0.25 × 100 = 25%
50 represents 25% of the total. The remaining 150 is 75%.
Price rose from $80 to $100. What is the % change?
= ((100 − 80) ÷ 80) × 100 = (20 ÷ 80) × 100 = +25%
A 25% increase. The absolute gain is $20.
$200 increased by 15%:
= 200 × (1 + 0.15) = 200 × 1.15 = $230
Amount added: $30. New value: $230.
$200 decreased by 15%:
= 200 × (1 − 0.15) = 200 × 0.85 = $170
Amount removed: $30. New value: $170. Note: to go back from $170 to $200 requires a 17.65% increase — not 15%.
Frequently asked questions
What is the basic formula for calculating a percentage?
Divide the part by the whole and multiply by 100. Formula: Percentage = (Part ÷ Whole) × 100. For example, 45 out of 60 gives (45 ÷ 60) × 100 = 75%.
How do I find X% of a number?
Multiply the number by the percentage divided by 100. Formula: Part = (% ÷ 100) × Whole. For 22% of 150: (22 ÷ 100) × 150 = 0.22 × 150 = 33. Use the "X% of Y" mode above.
How do I calculate percent increase?
Subtract the original value from the new value, divide by the original, then multiply by 100. From $80 to $100: ((100 − 80) ÷ 80) × 100 = 25% increase. Use the "% Change" mode — it auto-detects the direction.
Why is a 25% increase followed by a 25% decrease not back to zero?
Because the base changes between the two calculations. Starting at 100, a 25% increase gives 125. A 25% decrease from 125 gives 93.75 — not 100. The decrease applies to the larger number, so the same percentage removes more in absolute terms than it added. This is why symmetric percentage swings always result in a net loss.
What is the difference between percentage change and percentage points?
Percentage points measure the arithmetic difference between two percentages (e.g. 4% to 6% = +2 percentage points). Percentage change measures the relative shift: (6 − 4) ÷ 4 × 100 = +50%. A central bank raising rates from 2% to 3% is a +1 percentage point change, but a +50% change in the rate itself.
How do I find the original number before a percentage change?
Divide the final value by (1 + decimal) for an increase, or by (1 − decimal) for a decrease. If a price is $85 after a 15% discount, the original is $85 ÷ 0.85 = $100. This is called a reverse percentage. The key mistake to avoid: do NOT multiply the sale price by 1.15 — that gives the wrong answer because the percentage applied to the original, not the discounted price.
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Disclaimer
This calculator is for educational and planning purposes only. All results use standard percentage arithmetic with no rounding until display. For financial decisions involving tax rates, interest, or regulatory calculations, always verify the applicable rates with a qualified professional.