General · Popular

Percentage Calculator

A complete percentage calculator: find X% of Y, work out percentage change between two numbers, or run reverse-percentage calculations — all instantly.

Percentage

Value

Result

170

20% of 850 = 170

Quick insights

Half of 850 is 425.
10% of 850 is 85.

Method

How this calculator works

Percentages are fractions of 100 expressed as a value. Every percentage problem reduces to multiplication or division — the mode you pick determines the formula.

X% of Y           =  (X / 100) × Y
Y increased by X% =  Y + (X / 100) × Y
Y decreased by X% =  Y − (X / 100) × Y
A is what % of B  =  (A / B) × 100
% difference      =  |A − B| / ((|A| + |B|) / 2) × 100

Decide the mode that matches your question (X% of Y, increase, decrease, reverse, or difference).
Plug both numbers into the corresponding formula above.
For increase/decrease: multiply by (1 + X/100) or (1 − X/100) for a clean shortcut.
For reverse-percent: divide the part by the whole, then multiply by 100.
Round the result to the precision you need — 2 decimal places covers most everyday use.

Examples

Worked examples

Real numbers, end-to-end results.

20% of 850

= 170

Useful for tip, tax, or discount calculations.

$2,400 increased by 7.5%

= $2,580

A common annual-raise calculation.

300 is what % of 1,200?

= 25%

Reverse-percent: find the share, not the value.

Difference between 80 and 100

= 22.22%

Symmetric difference — useful for comparing experiments.

Use cases

When to use it

Calculate sales tax, tips, or store discounts on the fly.
Compare exam scores or growth rates.
Estimate annual salary raises or rent increases.
Convert ratios and proportions into something more readable.
Spot-check financial statements for percentage changes.

FAQ

Frequently asked questions

What does “20% of 850” mean?

It means 20 hundredths of 850 — that is 0.20 × 850 = 170. Use the X% of Y mode for this kind of calculation.

How do I calculate a percentage increase?

Switch to the Increase mode. Enter the original value and the percentage to add — the calculator shows the new value (e.g. 100 increased by 25% = 125).

What is the difference between percentage difference and percentage change?

Percentage change measures the directional shift from an old value to a new value. Percentage difference treats both values symmetrically — it is the absolute difference divided by their average. Use change for "before/after" comparisons and difference for two equal-status numbers.

Can I use negative numbers?

Yes. The reverse-percent and percent-of modes accept negatives — useful for losses, deficits, or temperature drops.

Why does “X is what % of Y” give a fraction sometimes?

Because percentages can be any real number. 5 is 50% of 10, but 5 is also 33.33% of 15.