Percentage Calculator

Seven calculation modes covering every common percentage problem. Live answers, visual breakdown, copy or save your work.

What is A% of B?

%

Example: 25% of 80 is 20.

A is what % of B?

Example: 20 is 25% of 80.

From A to B, what is the % change?

Example: 100 to 150 is a 50% increase.

Increase A by B%

%

Example: 100 plus 15% is 115.

Decrease A by B%

%

Example: 100 minus 25% is 75.

If A is the result of a B% , what was the original?

%

Example: 80 after a 20% discount means original was 100.

% difference between A and B

Direction-free comparison: difference over the average of magnitudes.

Result
. . .
Enter values to calculate

How to use

  1. Pick the calculation mode at the top.
  2. Enter the two values. The answer updates as you type.
  3. Use Copy to grab the result, or Save to keep a running history.
  4. The visual on the right adjusts proportionally so you can see the relationship at a glance.

Formulas used

  • % of: result = (A / 100) x B
  • X is what % of Y: result = (A / B) x 100
  • % change: result = ((B - A) / |A|) x 100
  • Add %: result = A x (1 + B/100)
  • Subtract %: result = A x (1 - B/100)
  • Reverse %: result = A / (1 +/- B/100)
  • % difference: result = |A - B| / ((|A| + |B|) / 2) x 100

Frequently asked questions

What percentage problems can I solve here?

Three of the most common: What is X% of Y, X is what percent of Y, and percent change from X to Y. Each one has its own tab with clear input labels.

How is percent change calculated?

Percent change equals (new value - old value) / old value × 100. A positive result is an increase; a negative result is a decrease.

How do I add or subtract a percentage from a number?

Add: multiply by 1 + p/100. Subtract: multiply by 1 - p/100. The calculator does this automatically on the percent-change tab when given a base and percentage.

Are the formulas explained?

Yes. Each tab shows the formula it uses below the inputs so you can double-check the result against your own working.

The three percentage questions, and which one you are asking

Almost every percentage problem is one of three shapes. "What is 18% of 250?" multiplies: 250 x 0.18 = 45. "120 is what percent of 400?" divides: 120 / 400 = 30%. "75 is 15% of what?" divides the other way: 75 / 0.15 = 500. Misreading which shape you are in is the single most common percentage mistake, and it is why this tool separates them into distinct modes instead of one ambiguous input.

Percent change vs percentage points

If an interest rate moves from 4% to 6%, it rose by 2 percentage points but by 50 percent. News reporting mixes these constantly. Percent change is always relative to the starting value: (new - old) / old x 100. That asymmetry also means changes do not cancel: a 20% drop followed by a 20% rise lands at 96% of where you started.

Common real-world conversions

  • Exam scoring: 43 correct out of 60 is 43/60 = 71.7%, independent of how the test is weighted per question.
  • Salary rises: a 4% raise on 1,850 EUR/month is 74 EUR. Two consecutive 4% raises compound to 8.16%, not 8%.
  • Shrinkflation: a chocolate bar going from 100 g to 85 g at the same price is a hidden 17.6% price increase per gram (100/85 = 1.176).
  • Statistics in headlines: "risk increased 40%" is meaningless without the base rate. From 0.1% to 0.14% is a 40% relative rise but 0.04 points absolute.

Keeping relative and absolute views side by side is the fastest way to sanity-check any percentage claim you read.

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