Finance

Percentage Calculator

Calculate what X% of a number is, what percent one number is of another, and the percent change between two numbers. Free, instant, no signup.

Percent (X)

Of number (Y)

Enter both numbers to see the answer.

All calculations happen in your browser. Nothing is stored.

✳ Free · No signup · Runs in your browser — we never store your numbers

Small business guide

What this tool helps you do

Use this free percentage calculator for the three percentage questions that come up constantly in business: what is X% of a number, what percent is one number of another, and what's the percent change between two numbers. Pick the mode, enter two numbers, and the answer appears as a plain sentence.

Percentages are where quick mental math quietly goes wrong — especially percent change, where the base matters. This calculator states each answer in words ("From 2,500 to 3,100 is a 24% increase") so there's no ambiguity about what the number means.

How to use this tool

1
Pick the mode: "What is X% of Y", "X is what % of Y", or "% change from X to Y".
2
Enter the two numbers — the labels update to match the mode.
3
Read the answer sentence. It states the result in words so the direction and base are unmistakable.
4
Switch modes to sanity-check the same numbers from a different angle.

Formula

X% of Y = X ÷ 100 × Y. X as a percent of Y = X ÷ Y × 100. Percent change from old to new = (new − old) ÷ |old| × 100.

Percent change always uses the old value as the base — growing from 100 to 150 is +50%, but falling from 150 to 100 is −33.3%.
"Percent" and "percentage points" differ: going from 10% to 15% is a 5-point rise but a 50% increase.
To reverse a percentage (X is 20% of what?), divide X by 0.20 — the "what percent" mode covers the common cases.
Results are rounded to two decimal places.

Examples

Commission on a sale

A maker pays a 15% marketplace commission on a $240 sale.

Inputs

Mode: What is X% of Y
X: 15, Y: 240

Result

15% of 240 is 36 — the marketplace keeps $36 and the maker nets $204.

Knowing the fee in dollars, not just percent, is what makes the pricing decision concrete.

Monthly revenue growth

A shop grew revenue from $2,500 in May to $3,100 in June.

Inputs

Mode: % change from X to Y
X: 2,500, Y: 3,100

Result

From 2,500 to 3,100 is a 24% increase.

Percent change makes months comparable at different scales — a $600 jump means something different at $2,500 than at $25,000.

Key terms

Base value

The number a percentage is measured against. In percent change it's always the old value — changing the base changes the answer.

Percentage points

The arithmetic difference between two percentages. A margin moving from 30% to 35% rose 5 points, which is a 16.7% relative increase.

How to interpret the result

Direction and base matter more than the digits

The same two numbers give different percentages depending on which is the base: 20 is 25% of 80, but 80 is 400% of 20. The answer sentence names both numbers precisely so the result can't be misread.

Percent change is asymmetric

A 50% drop needs a 100% gain to recover. When revenue falls and rebounds by the "same percent," you're not back where you started — check the absolute numbers before celebrating.

Common mistakes

Using the new value as the base for percent change, which understates drops and overstates gains.
Confusing a percentage-point difference with a percent change when comparing rates or margins.
Chaining percentages by adding them — a 20% discount followed by 10% off is 28% total, not 30%.
Rounding intermediate steps and wondering why the final figure is off by a few cents.

Frequently asked questions

Is this percentage calculator really free?+

Yes — free, no signup, no limits. Use any mode as often as you like.

Do you store my numbers?+

No. The math runs entirely in your browser; nothing is sent to a server or stored.

How do I calculate the percentage of a number?+

Divide the percentage by 100 and multiply by the number: 15% of 240 is 0.15 × 240 = 36. That's the first mode of this calculator.

What is the difference between percent change and percentage points?+

Percent change is relative to the starting value; percentage points are the simple difference between two percentages. A rate going from 10% to 15% is +5 points but a +50% change.

How do I reverse a percentage?+

If X is P% of some unknown, divide X by (P ÷ 100): if 36 is 15% of something, 36 ÷ 0.15 = 240. The "X is what % of Y" mode handles the common everyday cases.

Which business numbers is this useful for?+

Commissions, fee structures, growth rates, tips, deposits, and quick sanity checks. For dedicated jobs use the Discount Calculator, Profit Margin Calculator, or Sales Tax Calculator — they show the work for those specific decisions.