A free percentage calculator with 5 modes: find the percentage
of a number, work out what percent one number is of another, compute
percentage change, reverse a percentage, or add and subtract a percentage
for markup and discount problems. This free online tool runs
instantly in your browser and shows every step of the calculation —
formula, substitution, and result — so you can learn the math, not just
copy the answer.
✓ Free, no signup✓ 5 calculation modes✓ Shows the working✓ Instant results
Quick answer: To find the percentage of a number, divide the part
by the whole and multiply by 100. The basic percentage formula is
Percentage = (Part ÷ Whole) × 100. For example, 15 out of 60
equals (15 ÷ 60) × 100 = 25%. To find a percent of a number, the
formula reverses: Result = (Percent ÷ 100) × Number, so 25% of
80 = (25 ÷ 100) × 80 = 20. The calculator above handles
both directions plus percentage change, reverse percentage, markup, and
discount in one tool.
What is X% of Y?
%
Result
—
Enter a percentage and a number
X is what percent of Y?
Result
—
Enter the part and the whole
Percentage change from A to B
Percentage change
—
Enter a starting and ending value
X is Y% of what number?
%
Original value
—
Enter the known value and the percentage
SubtractX% from Y (discount)
%
Final amount
—
Enter a starting amount and percentage
The percentage formula is one of the most-used calculations in everyday math — this percentage calculator handles every common variation. Photo by Antoine Dautry on Unsplash.
How to use this percentage calculator (5 modes)
This free online percentage calculator gives you five focused tools in a
single interface. Click the tab that matches your problem, type two values,
and the tool shows the answer plus the formula it used:
% of a Number — "What is 25% of 80?" Enter the percentage and
a given number. Returns 25% × 80 = 20.
Find % — "15 is what percent of 60?" Enter the part (numerator)
and the whole (denominator). Returns the percentage value 25%.
% Change — "From 100 to 125?" Enter a starting and ending
value. Returns the percent change between two values, with a
positive (increase) or negative (decrease) sign and the absolute
difference.
Reverse % — "20 is 25% of what number?" Enter the part and
percentage. Returns the original whole.
Markup / Discount — Adds or subtracts a percent of x from a
starting amount. Toggle between Add (markup) and Subtract (discount).
Returns the final price and the amount changed.
Each result panel includes a Copy button to grab the answer for
notes, spreadsheets, or messages, plus the full working — formula,
substituted numbers, and final value — so you can show your math.
The percentage formula explained
A percentage is just a number expressed as a fraction of 100. The word
"per cent" literally means "out of 100", and the percent sign (%) is the
notation we use for that. According to the
Wikipedia
reference on percentages, a percentage is a dimensionless number,
expressed as a fraction of 100 — so 50% means 50 parts per 100, or one
half. The basic percentage formula every percentage calculation uses is:
Percentage = ( Part ÷ Whole ) × 100
That equation has three variables — Part, Whole, and Percentage. If you
know any two, you can compute the third. This is why a good percentage
calculator has multiple modes: the equation stays the same, but the
unknown changes.
Example. A test has 60 questions and you get
15 right. To find your score: ( 15 ÷ 60 ) × 100 = 25%. The same
formula tells you 15 is the part, 60 is the whole, and 25% is the
resulting percentage value.
How this percentage calculator finds a percentage of a number
Finding a percentage of a number is the most common percentage
calculation — used for tips, sales tax, commissions, interest rates, and
hundreds of other real-world percentage problems. Rearrange the basic
percentage formula to solve for the result:
Result = ( Percentage ÷ 100 ) × Number
The "÷ 100" step converts the percent into its decimal form. So 25%
becomes 0.25, and "25% of 80" becomes 0.25 × 80 = 20. The percentage
calculator above does this in milliseconds, but knowing the equation lets
you double-check the answer in your head.
Example — sales tax. A $120 purchase with 8.5%
sales tax: ( 8.5 ÷ 100 ) × 120 = $10.20 in tax. Total: $130.20.
How to calculate percentage change with this percentage calculator
Percentage change measures how much a number has grown or shrunk
compared to its original value. Investopedia's
percentage
change reference gives the standard formula:
% Change = ( New − Old ) ÷ Old × 100
A positive result is a percentage increase, a negative result is a
percentage decrease. The percentage change calculator tab uses this exact
formula and shows both the direction (increase / decrease) and the
absolute change between two numbers.
Example. From 100 to 125: ( 125 − 100 ) ÷ 100 × 100
= +25% increase. From 80 to 60: ( 60 − 80 ) ÷ 80 × 100 =
−25% decrease.
Percentage change is asymmetric — a 25% increase followed by a 25%
decrease does not bring you back to the start. From 100 → +25% =
125 → −25% = 93.75. This is one of the most common percentage problems
people get wrong by intuition, which is exactly why a calculator is useful.
Reverse percentage: what is X a percent of?
The reverse percentage mode answers the question "this number is some
percent of what?" — useful when you know a portion of a whole but need to
find the total. Rearrange the percentage formula to solve for the whole:
Whole = Part ÷ ( Percentage ÷ 100 )
For example, if your shop's commission of $150 is 5% of total sales,
total sales = 150 ÷ ( 5 ÷ 100 ) = 150 ÷ 0.05 = $3,000. Reverse
percentage is the math behind tipping back-solves, finding pre-tax prices,
and many percentage-of-the-total problems.
Markup, discount, and other real-world percentage calculations
The Markup / Discount tab handles a different kind of percentage problem:
taking a starting amount and either adding or subtracting a percentage of
it. This is the math behind sale prices, sales tax, gratuities, and
business markups. The
Khan
Academy lesson on percent word problems walks through several worked
examples of these everyday calculations:
Discount — Subtract X% from Y. A $80 shirt at 25% off:
80 − (0.25 × 80) = 80 − 20 = $60. The amount saved is
$20.
Markup — Add X% to Y. A wholesale item costing $40 with a
30% retail markup: 40 + (0.30 × 40) = 40 + 12 = $52.
Sales tax — Same math as markup, treated as a tax instead of
a profit margin.
Tip / gratuity — Add X% to a bill. A $48 meal with 18% tip:
48 + 8.64 = $56.64.
Sale tags use percentage discounts everywhere — the percentage calculator above computes the final price and the savings amount in one step. Photo by Artem Beliaikin on Unsplash.
Percentage points vs percent change
One trap to watch for involving percentages: percentage points
are not the same as percent change. Percentage points measure the absolute
difference between two percentages; percent change measures the relative
difference between two values.
Interest rates rising from 4% to 5% is a 1 percentage point
increase — but a 25% increase in the rate itself.
An election poll moving from 40% to 44% support is a 4 percentage
point gain — but a 10% relative gain.
News articles and financial reports often confuse the two. The
calculator above only computes percent change (the relative
measure); for percentage point differences, simply subtract the two
percentages.
Convert a percentage to a fraction or decimal
Because percent means "per 100", you can convert any percentage to a
fraction or decimal by dividing by 100. For deeper background,
Math
is Fun's percentage page covers the conversions with extra examples.
Percentage
Decimal form
Fraction
1%
0.01
1/100
5%
0.05
1/20
10%
0.10
1/10
20%
0.20
1/5
25%
0.25
1/4
33.33%
0.333
1/3
50%
0.50
1/2
75%
0.75
3/4
100%
1.00
1/1
200%
2.00
2/1
To go the other way: multiply a decimal or fraction by 100 to express
the same number as a percentage. So 0.6 = 60%, and 3/4 = 75%.
Common percentage problems and worked examples
Here are the percentage problems people search for most, with each
answer computed by this free online tool:
What is 20% of 50? — 0.20 × 50 = 10
What percent is 12 of 80? — ( 12 ÷ 80 ) × 100 =
15%
What is the percentage change from 250 to 300? —
( 300 − 250 ) ÷ 250 × 100 = +20%
9 is 30% of what number? — 9 ÷ 0.30 = 30
A $120 jacket marked 40% off: 120 − (0.40 × 120) =
$72 (you save $48)
Add 7% tax to $65: 65 + (0.07 × 65) = $69.55
50 out of 100 as a percentage: ( 50 ÷ 100 ) × 100 =
50%
What is 0% of anything? Always zero — multiplying by
zero gives zero, no matter the first number.
Percent error and percent difference
Two closely related calculations involving percentages aren't part of
this basic percent calculator, but they're worth knowing:
Percent error measures how far an experimental value is from
a known correct value:
| (Experimental − Actual) ÷ Actual | × 100. It's almost
identical to percent change but always reported as a positive
number.
Percentage difference (sometimes called percent difference)
compares two values when neither is "original":
| A − B | ÷ ( (A + B) ÷ 2 ) × 100. Use this when comparing
two measurements of equal status — for example, two different
sensor readings of the same temperature.
Britannica's
entry
on percentage traces the term back to the Latin per centum
and covers how percentages relate to fractions, ratios, and proportions.
Students, accountants, shoppers, and analysts all reach for the same percentage formula — this free percentage calculator from Anchor AI Tools shows the working every time. Photo by Chris Liverani on Unsplash.
Why our percentage calculator is accurate
This percentage calculator uses the exact same percentage formula
documented in every introductory algebra textbook — no rounding tricks, no
hidden assumptions. The computation runs in JavaScript inside your
browser, so your numbers never leave your device, and the result is
displayed to two decimal places by default. For very small or very large
percentages, the tool switches to the precision needed
to show meaningful digits.
Every result includes the formula used and the substituted values, so
you can verify the math by hand. If you spot an edge case where the
calculator gives a result you disagree with, the working is
right there to compare against your own calculation.
Percentage calculator FAQs
What is the percentage formula?
The basic percentage formula is
Percentage = (Part ÷ Whole) × 100. For example, 15 out of 60
equals (15 ÷ 60) × 100 = 25%. Rearranging the same equation lets you
find any one variable when you know the other two.
How do I find a percentage of a number?
Divide the percentage by 100 to convert it to a
decimal, then multiply by the number. So 25% of 80 = (25 ÷ 100) × 80
= 0.25 × 80 = 20. The "% of a Number" tab in this percentage
calculator does this in one click.
How do I calculate percentage change?
Use the formula
(New − Old) ÷ Old × 100. From 100 to 125 is a 25% increase;
from 80 to 60 is a 25% decrease. The percentage change calculator tab
handles both directions automatically.
What's the difference between percent change and percentage points?
Percentage points measure the absolute difference
between two percentages. Percent change measures the relative
difference. Interest rates rising from 4% to 5% is a 1 percentage
point increase but a 25% percent change in the rate itself.
Is this a free percentage calculator?
Yes. The percentage calculator from Anchor AI Tools
is completely free to use, with no signup, no download, and no
limits. It runs entirely in your browser.
Can I use this percentage calculator for tips and discounts?
Yes. Use the Markup / Discount tab — toggle Subtract
for a discount, toggle Add for markup, sales tax, or a tip
calculation. The percentage calculator shows the final amount and the
amount added or saved.
How do I convert a percentage to a decimal?
Divide by 100. 25% becomes 0.25; 7.5% becomes 0.075.
To convert a decimal back to a percentage, multiply by 100.
How do I convert a percentage to a fraction?
Write the percent as a number over 100 and simplify.
25% = 25/100 = 1/4. 50% = 50/100 = 1/2. The conversion table on this
page lists the most common values.
What does 100% mean? What about 200%?
100% equals the whole — same as 1 in decimal form or
1/1 as a fraction. 200% means twice the whole, or 2 in decimal form.
Percentages above 100% are valid and common in finance, statistics,
and growth rates.
Why does the percentage calculator show the formula?
Because seeing the working helps you trust the
answer and learn the math. Every result panel shows the percentage
formula used and the substituted numbers, so you can verify the
calculation by hand.
What is a percent of zero?
Any percent of zero is zero — multiplying by zero
gives zero regardless of the first number. The percentage calculator
handles the zero case gracefully and just returns 0.
Can the percentage calculator handle decimals and negative numbers?
Yes. Enter any decimal value such as 7.5 or 33.33,
and the percentage calculator will compute the result accurately.
Negative numbers are allowed for percentage change (showing a
decrease) and reverse percentage calculations.
This percentage calculator from Anchor AI Tools provides
estimates for general information and education only. For high-stakes
financial, scientific, or engineering calculations, always confirm the
computation by hand or with a qualified professional.
