Home / Percentage calculator

Percentage calculator

Work out percentages instantly: X% of a number, what percentage one number is of another, percentage increase and decrease, and discounts. Free, with the formula and working shown for every answer.

What is % of ?

3020% of 150 is 30.

Working: 20 ÷ 100 = 0.2 · 0.2 × 150 = 30

is what % of ?

75%45 is 75% of 60.

Working: 45 ÷ 60 = 0.75 · 0.75 × 100 = 75%

From to

+20%An increase of 20%.

Working: (120 − 100) ÷ 100 = 0.2 · 0.2 × 100 = 20%

% off £

£60You pay £60, saving £20.

Working: 80 × (1 − 0.25) = £60

Results update as you type. Nothing you enter is stored or sent anywhere. Free to use, no signup

How to calculate a percentage

A percentage is a fraction of 100. The word comes from the Latin per centum, meaning by the hundred, and that is exactly how the maths works: 20% means 20 parts of every 100. Once you hold onto that, every percentage calculation becomes one of a handful of simple patterns, and this page covers the four you will actually meet in real life.

What is X% of a number?

This is the most common percentage question there is: working out a tip, a deposit, VAT, or a commission. Divide the percentage by 100 to turn it into a decimal, then multiply.

X% of Y = (X ÷ 100) × Y

Example: what is 20% of £150? 20 ÷ 100 = 0.2, and 0.2 × 150 = £30. A handy shortcut: 10% is just the number with the decimal point moved one place left (£15), so 20% is double that.

What percentage is one number of another?

Use this when you have a part and a whole: marks out of a total, a deposit against a house price, or sales from one product against all sales. Divide the part by the whole, then multiply by 100.

X as a % of Y = (X ÷ Y) × 100

Example: you scored 45 out of 60. 45 ÷ 60 = 0.75, and 0.75 × 100 = 75%.

Percentage increase and decrease

This one measures change between two values: a price rise, revenue growth, a drop in costs. Take the difference between the new and original values, divide by the original, and multiply by 100. Dividing by the original number rather than the new one is the step people most often get wrong.

% change = ((New − Original) ÷ Original) × 100

Example: revenue went from £1,000 to £1,500 a week. (1,500 − 1,000) ÷ 1,000 = 0.5, so that is a 50% increase. If it fell from £1,500 to £1,000, that is (1,000 − 1,500) ÷ 1,500 = −0.333, a 33.3% decrease. The percentage is different in each direction because the starting point changed, which is also why a 50% drop needs a 100% rise to get back to where you started.

Working out a discount

To find a sale price, subtract the discount from 100%, convert to a decimal, and multiply by the original price. This is quicker than working out the discount amount and subtracting it.

Sale price = Y × (1 − X ÷ 100)

Example: 25% off £80 is 80 × 0.75 = £60. For stacked offers like an extra 10% off an already reduced price, apply each discount in turn rather than adding them together: 20% off then 10% off is 0.8 × 0.9 = 0.72, a total of 28% off, not 30%.

Percentages in business and marketing

We built this calculator because percentages are the working language of commercial decisions, and we use these exact calculations with clients every week. A few of the places they matter most:

Margin. If a product sells for £40 and costs £25 to make and ship, the margin is (40 − 25) ÷ 40 = 37.5%. Margin is a percentage of the selling price; markup is a percentage of the cost. Mixing them up flatters your numbers.
Growth. Comparing this month to last month, or this year to last year, is a percentage change calculation, and the divide by the original rule is what keeps year-on-year comparisons honest.
Conversion rate. Orders divided by visitors, times 100. If 25,000 people visit and 500 buy, that is a 2% conversion rate, and lifting it to 2.4% is itself a 20% improvement, which is the kind of compounding arithmetic that makes conversion work so valuable.
Discounting. A 20% discount usually costs far more than 20% of profit. On the £40 product above with £15 of profit, a £8 discount gives away more than half the profit on every sale. Running the percentage before running the promotion is the difference between a sale and a giveaway.
VAT. Adding 20% VAT is price × 1.2. Removing it is price ÷ 1.2, not price × 0.8, another asymmetry that catches people out.

If those last few feel close to home, that is the day job: we are a D2C marketing practice and this kind of arithmetic sits underneath every recommendation we make, from paid media to email.

Frequently asked questions

How do I work out a percentage of a number without a calculator?

Anchor on 10%: move the decimal point one place to the left. From there, build the percentage you need. For 35% of £60: 10% is £6, so 30% is £18, and 5% is half of £6, giving £3. Total: £21.

Why is a percentage increase not the same as the decrease back?

Because the starting point changes. Going from 100 to 150 is a 50% increase (measured against 100), but going from 150 back to 100 is a 33.3% decrease (measured against 150). Always ask: percentage of what?

What is the difference between percentage points and percent?

If a conversion rate moves from 2% to 3%, it has risen by one percentage point, but by 50% in relative terms. Percentage points subtract; percentages compare.

How do I add or remove VAT?

To add 20% VAT, multiply the net price by 1.2. To remove VAT from a gross price, divide by 1.2. Dividing, not multiplying by 0.8, because the VAT was calculated on the smaller net figure, not the larger gross one.

Is this calculator free? Do you store what I type?

Free, no signup, and nothing you enter leaves your browser. The calculations run on the page itself.

Good with numbers. Better with growth.

We are a D2C marketing practice that measures everything the way this page does: honestly, and against an objective agreed up front.

See if you’re a fit →