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Percentage Calculator: 5 Percent Calculations at Once, With the Formula
Five percentage calculators in one: type your numbers and get the answer and the formula instantly. Built for prices, discounts, sales tax and marketing metrics.
Percent of a number
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What percent is it
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Percentage change
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Add or subtract a percentage
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Original amount (tax and discounts)
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Everything is calculated in your browser: nothing is saved or sent. Decimals and negative numbers work too.
This percentage calculator handles the five percent problems you actually run into: budgets, conversion rates, growth, markdowns and sales tax. Every card works at the same time and shows the formula right under the answer.
How to use the percentage calculator
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Pick the card that matches your question
Each card answers one question: what is X% of Y, what percent is X of Y, how much did it change, what do you get when you add or subtract a %, and what was the original amount.
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Swap the sample numbers for yours
Every card comes loaded with a marketing example. Type over it and the answer updates as you go. Decimals and negative numbers work too.
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Choose add or subtract
In cards 4 and 5 you choose whether the percentage is added or subtracted. Sales tax is added; a markdown is subtracted.
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Copy the answer with its formula
“Copy” gives you the sentence and the math, ready for a report or an email.
How to calculate percentage: the 5 formulas
A percentage is a fraction of 100: 15% of something is 15 parts out of every 100. Everything in the calculator comes from that:
| What you want to know | Formula |
|---|---|
| 1. X% of Y | Y × X ÷ 100 |
| 2. X is what % of Y | X ÷ Y × 100 |
| 3. Change from X to Y | (Y − X) ÷ X × 100 |
| 4. Y plus or minus X% | Y × (1 ± X ÷ 100) |
| 5. Original before X% | Y ÷ (1 ± X ÷ 100) |
Formula 1 is how to calculate percentage of a number, the one everybody knows. Formula 5 is the one most people get wrong: undoing a percentage means dividing, not subtracting.
Percentage examples for marketing
These are the cases the calculator loads by default:
| What you want to know | Card | Example | Answer |
|---|---|---|---|
| How much of the budget goes to Meta | 1 | 15% of $2,400 | $360 |
| Your conversion rate | 2 | 45 sales out of 1,800 visits | 2.5% |
| How much your followers grew | 3 | from 1,200 to 1,500 | +25% |
| The price after a markdown | 4 | $80 minus 15% | $68 |
| The price before sales tax | 5 | $108.25 with 8.25% tax | $100 |
For stacked coupons or a buy one, get one free deal, the percent off calculator turns them into a real discount. And if the percentage you care about is what you keep from each sale, the margin calculator separates margin from markup.
Percentage of a percentage: how to calculate it
Convert both percentages to decimals and multiply them. 50% of 50% is 0.50 × 0.50 = 0.25, so 25%. You never add or subtract them. Say you email a newsletter to 20,000 subscribers (made-up numbers): 30% open it, and 5% of those openers click.
| Step | Calculation | Result |
|---|---|---|
| Opens | 20,000 × 30% | 6,000 |
| Clicks | 6,000 × 5% | 300 |
| Click rate on the whole list | 300 ÷ 20,000 | 1.5% |
That 1.5% comes from 0.30 × 0.05. With both percentages under 100%, the answer is always smaller than either of them, because each step keeps only a slice of the one before. On the calculator, chain it with card 1: take 30% of 20,000, then 5% of the result. The classic mistake is reporting a 5% click rate when the base is openers, not the whole list. Always say what each percentage is a percentage of.
Percentage increase calculator: from a starting to a final value
Card 3 doubles as a percentage increase calculator and a percent change calculator. Here is how to calculate percentage increase: subtract the old value from the new one, divide by the old value and multiply by 100. It works the same for sales, prices, traffic or followers.
Two traps worth knowing:
- Up and down by the same amount doesn’t cancel out. A $100 price that goes up 20% becomes $120. Cut it by 20% and you land at $96, because that 20% comes off $120.
- There is no percent change from zero. Going from 0 to 50 customers isn’t an “infinite percent” increase. The calculator tells you so and shows the difference instead.
To see whether a campaign makes money, not just numbers that go up, check the ROI calculator.
Percentage difference vs percent change: which formula to use
Percent change has a direction: it goes from a starting value to a final one. Percentage difference compares two values with no “before,” so it divides by their average. Take two ad sets that brought in 80 and 100 leads (made-up numbers).
| Formula | Calculation | Result |
|---|---|---|
| Percent change, 80 to 100 | (100 − 80) ÷ 80 × 100 | +25% |
| Percent change, 100 to 80 | (80 − 100) ÷ 100 × 100 | −20% |
| Percentage difference | 20 ÷ ((100 + 80) ÷ 2) × 100 | 22.2% |
The same pair gives +25% or −20% depending on the direction, so always say which number is the starting point. Reports almost always have a baseline, such as last month or the control ad, so percent change is the one you want. It is card 3 of the calculator. Use percentage difference only when neither number is the baseline, such as two channels measured over the same period.
Frequently asked questions about percentages
What is 20% of 70?
14. Multiply 70 by 20 and divide by 100, or just multiply 70 by 0.2. A quick mental route: 10% of 70 is 7 (move the decimal point one place to the left), and 20% is twice that. The same trick gets you 5% (half of 10%) and 15% (10% plus 5%), which covers most tips, commissions and budget splits without reaching for your phone.
How do I calculate a percentage of another number?
Divide the part by the total and multiply by 100. If 45 out of 1,800 visitors bought something, 45 ÷ 1,800 × 100 = 2.5%, which is your conversion rate. The order matters: the number you are measuring goes on top, the whole goes underneath. Swap them and you get 4,000%, which is a good sign you divided the wrong way round. Card 2 of the calculator does this for you.
How do I calculate a percentage in Excel?
Put the part in A2 and the total in B2, type =A2/B2 in C2 and format C2 as a percentage. For a percent of a number, use =B2*15% or =B2*A2 if A2 holds the percentage. For percent change, use =(B2-A2)/A2. Excel stores 15% as 0.15, so never multiply by 100 when the cell is already formatted as a percentage, or you get 1,500%.
How do you calculate percentage increase?
Subtract the starting value from the new value, divide by the starting value and multiply by 100. Going from 1,200 to 1,500 followers is (1,500 − 1,200) ÷ 1,200 × 100 = 25%. Always divide by where you started, not where you ended: dividing by 1,500 gives 20%, a different and wrong answer. If the result comes out negative, it is a percentage decrease.
How do I calculate sales tax?
Multiply the pre-tax price by your combined state and local rate. At 8.25%, a $100 item carries $8.25 in tax, so you pay $108.25. To back the tax out of a total, divide instead of subtracting: $108.25 ÷ 1.0825 = $100. Taking 8.25% off $108.25 gives $99.32, which is wrong because the tax was calculated on the $100, not on the total. Card 5 does the division.
How do you calculate percentage decrease?
Subtract the new value from the starting value, divide by the starting value and multiply by 100. If your email list drops from 5,000 to 4,600 subscribers, (5,000 − 4,600) ÷ 5,000 × 100 = 8%. Always divide by where you started. A drop of 8% followed by a rise of 8% does not bring you back: 4,600 × 1.08 = 4,968, not 5,000. If you run the increase formula instead, a negative result simply means a decrease.