How do I find X% of a number?

Multiply the number by the percentage and divide by 100. For example, 15% of 200 is (15 ÷ 100) × 200 = 30. The first calculator does this for you as you type.

How do I calculate percentage increase or decrease?

Subtract the original value from the new value, divide by the original value, then multiply by 100. A positive result is an increase; a negative result is a decrease.

Is the calculator private?

Yes. Every calculation runs entirely in your browser with JavaScript. Nothing you type is ever sent to a server or stored.

Percentage Calculator — Percent Of, Percentage & Change

Percentage Calculator

Three quick percentage tools in one. Find X% of a number, work out what percent one number is of another, or calculate the percentage increase or decrease between two values — all updating live as you type.

What is X% of Y?

Percentage (X)

Of (Y)

—

Result

X is what percent of Y?

Value (X)

Total (Y)

—

X as % of Y

Percentage change from X to Y

From (X)

To (Y)

—

Change

🔒 100% private — runs in your browser, never uploaded.

How to use it

What is X% of Y? — enter the percentage and the total. Example: 15% of 200 = 30. Handy for tips, discounts and tax.
X is what percent of Y? — enter a part and a whole to see the part as a percentage. Example: 30 out of 120 = 25%. Great for test scores and shares of a total.
Percentage change from X to Y — enter an old value and a new value to see the percentage increase or decrease. Example: 80 → 100 = +25%.

Every box recalculates the instant you change a number, so you can experiment freely without pressing a button.

The percentage formulas

Behind the scenes the calculator uses three classic formulas. Percent of a number: (X ÷ 100) × Y.One number as a percent of another: (X ÷ Y) × 100. Percentage change:((new − old) ÷ |old|) × 100. Using the absolute value of the original number keeps the sign of the change correct even when you start from a negative value.

Common real-world uses

Tips & tax: quickly add 10%, 15% or 20% to a bill.
Sales & discounts: find how much you save, or the price after a percent-off deal.
Grades & scores: turn “38 out of 50” into a percentage.
Growth tracking: measure how much a price, audience or metric grew or shrank.

A quick note on percentage change: a rise from 50 to 100 is a 100% increase, but the reverse — 100 back down to 50 — is only a50% decrease. The percentages aren’t symmetrical because each is measured against its own starting value, which is exactly why a dedicated calculator helps avoid mistakes.

Is it private?

Yes. The Percentage Calculator is plain JavaScript that runs entirely inside your browser tab. The numbers you enter are never uploaded, logged or stored anywhere — there are no accounts and no tracking of your inputs. You can even use it offline once the page has loaded.

Frequently asked questions

Why does “what percent of” show a dash when the total is 0?

Dividing by zero is undefined, so there’s no meaningful percentage when the total (Y) is 0. Enter a non-zero total to get a result.

Can it handle decimals and negative numbers?

Yes — all three calculators accept decimals and negative values, and results are rounded to a few decimal places for readability.

What’s the difference between percentage points and percent?

Going from 10% to 15% is a 5 percentage-point rise, but a 50% increase in relative terms. This tool reports relative percentage change.

Results are rounded for display; for accounting or exams, double-check critical figures.