Toolivaro

Free Percentage Calculator

Four percentage calculations in one tool: X% of Y, X is what % of Y, % change from X to Y, and Y plus or minus X%.

The percentage calculator covers the four percentage questions that come up in everyday math, shopping, and business: what is X percent of a number, what percentage one number is of another, the percentage change between two values, and increasing or decreasing a value by a percentage. Switch between the four modes to answer "how much is 15% of 80?", "what percent of 200 is 45?", "what is the percent change from 120 to 150?", or "what is 90 plus 12%?" in one place — no more remembering which formula applies to which phrasing. All arithmetic runs with exact decimal math, so fractional percentages like 33.3% of 99.99 are computed precisely and rounding is applied only to the displayed result. Percentage change returns both the percentage and the absolute difference, which makes the tool useful for price moves, growth rates, and markup checks. Everything is calculated locally in your browser — no values are sent to any server.

Processed locally in your browser

The percentage, e.g. 25 for 25%.

How is the result calculated?

What is 25% of 120?

A store offers 25% off an item priced at 120.00. In percentage-of mode, 120 × 25 / 100 = 30, so the discount is exactly 30.00.

Input Value
mode percentOf
percent 25
base 120
Result 30

Sales grew from 100 to 150 — by how much?

In change mode with from 100 and to 150, the percentage change is (150 − 100) / 100 × 100 = 50%, with an absolute difference of 50.

Input Value
mode change
from 100
to 150
Result +50% · difference 50

What is the formula and its assumptions?

Percentage of a number

result = Y × X% / 100

Symbol Meaning
X% the percentage
Y the base number

What percentage of a number

result = X / Y × 100

Symbol Meaning
X the part
Y the whole

Percentage change

change % = (to − from) / from × 100

Symbol Meaning
from the original value
to the new value

Add or subtract a percentage

result = Y × (1 + X/100)

Symbol Meaning
Y the base number
X% the percentage to add (negative to subtract)

What are the most common mistakes?

  • Confusing percent-of with percent-change — 50% of 100 and a 50% increase of 100 give different answers (50 vs 150).
  • Measuring a percentage change against the new value instead of the old one — a change from 100 to 150 is +50%, while 150 to 100 is −33.33%.
  • Entering a percentage as a decimal (0.25 instead of 25) and getting a result off by a factor of 100.

What are the assumptions and limitations?

  • The change mode requires a non-zero starting value — percentage change is undefined from zero.
  • Results are mathematical values, not financial advice; for pricing and margin decisions see the business calculators.
  • Values are rounded for display only; the underlying calculation keeps full precision.

Where do the numbers come from?

Last reviewed August 11, 2026 · Version 1.0.0 · Toolivaro does not guarantee external content.

Business Discount Calculator Calculate the final price after any percentage discount, the exact amount saved, and the discount between two prices. Business Markup Calculator Calculate markup percentage, markup amount, and the selling price you need from any cost figure, with a margin cross-check. Business Profit Margin Calculator See profit margin and markup percentages side by side from revenue and cost — with gross profit and rounding you control. Business Break-Even Calculator Find how many units you must sell — and at what revenue — to cover your fixed costs, from price and variable cost.

Frequently asked questions

What is the difference between percent change and percent of?

"X% of Y" scales one number by a percentage; "percent change from A to B" measures how much B grew or shrank relative to A. For example 50% of 100 is 50, but a change from 100 to 150 is also a 50% increase — the same percentage describes two different calculations, which is why the calculator separates the modes.

Why is a decrease from 150 to 100 not −50%?

It is −33.33%. Percentage change is measured against the starting value: (100 − 150) / 150 × 100 = −33.33%. A 50% decrease would be a change from 150 to 75. The percentage always depends on which side is the base, and the calculator applies the convention consistently.

Can I use negative percentages?

Yes, in the add-or-subtract mode a negative percentage subtracts: "90 plus −10%" gives 81. In change mode, negative results simply mean the value decreased.

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