Calculators

Percentage Calculator

Percentage, increase and decrease calculations

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About this tool

The Percentage Calculator answers the three most common percentage questions on one page, with all three panels visible at once so you never have to switch modes. The first panel finds a percentage of a number (what is 18% of 85.50?), the second shows what percentage a part is of a whole (47 out of 60), and the third measures the percent change from an original value to a new value and labels it as an increase or a decrease. Every panel recalculates as you type and starts with sample values so you can see how it works. Students checking exam scores, shoppers working out a discount, and analysts comparing month-over-month figures can get an answer in seconds. Results are formatted with up to four decimal places, and the tool warns you instead of dividing by zero when the whole or the original value is 0. All maths runs in your browser.

Why use it

  • Three Questions on One Page: Percent of a number, part of a whole, and percent change each have their own panel, all visible together, so you can answer related questions without switching modes or re-entering numbers.

  • Live Results: Every panel recalculates on each keystroke, so you can try different numbers and immediately see how the answer moves.

  • Clear Direction on Changes: The percent-change panel shows the size of the change and labels it as an increase or a decrease, so growth and decline are never confused.

  • Divide-by-Zero Guard: If the whole or the original value is 0, the tool shows a short message instead of a meaningless result.

  • Mobile-friendly: Large input fields and a layout that reflows to a single column on small screens make it practical on a phone in a store aisle or at a restaurant table.

How to use

  1. Use the first panel to find a percentage of a number: enter the Percentage (%) and the Of number
  2. Use the second panel to see what share a Part is of a Whole
  3. Use the third panel to compare an Original value with a New value
  4. Read each result as you type; no Calculate button is needed
  5. Check the label under the change result to see whether it is an increase or a decrease

When it helps

  • Calculating tax, tip, or service charge as a percentage of a bill amount
  • Finding your exam or test score as a percentage of the total available marks
  • Computing the year-over-year or month-over-month growth rate between two revenue figures
  • Checking how much a price went up or down between two receipts
  • Figuring out how much money you save on a discounted item before purchasing
  • Expressing a survey result, budget allocation, or composition as a percentage of the whole

Examples

What is 18% of $85.50

Input

Percentage (%): 18, Of number: 85.50

Expected result

15.39

Score as percent

Input

Part: 47, Whole: 60

Expected result

78.3333%

Price increase

Input

Original value: 1200, New value: 1350

Expected result

12.5% ↑ increase

Tips

  • To add a percentage to a value, find the percentage in the first panel and add it to the number yourself
  • Read the increase/decrease label under the change result — the number itself is shown without a sign
  • When compounding two percentages, apply them sequentially, not by adding them together
  • Results can carry up to four decimals — round to two before using them as currency
  • Pair with the Discount Calculator when you also need to see the total savings in currency terms

Frequently Asked Questions

What is the difference between a percent and a percentage point?
A percent expresses a ratio relative to a base value — 20% of $100 is $20. A percentage point is the arithmetic difference between two percentages — if interest rises from 2% to 3%, that is a one percentage point increase, not a 1% increase. Confusing these two is one of the most common errors in financial reporting.
How do I find the original price before a percentage was added?
Divide the final amount by (1 + rate/100). For example, a gross total of ₹1,180 at 18% GST came from ₹1,180 ÷ 1.18 = ₹1,000. This calculator does not have a reverse mode, so do that division yourself, or use the GST Calculator, which can remove tax from an inclusive amount.
Why does a 50% increase followed by a 50% decrease not return the original?
Because each percentage operates on a different base. Starting with 100, a 50% increase gives 150, and a 50% decrease of 150 gives 75 — not 100. Percentage changes are multiplicative, not additive, so they don't simply cancel each other out.
How do I compute year-over-year growth?
Use the third panel: enter last year's figure as the Original value and this year's as the New value. The formula is ((new − old) / old) × 100. The result shows the size of the change, and the label underneath says whether it is an increase or a decrease.
How many decimal places are shown?
Results are shown with up to four decimal places, and trailing zeros are dropped. For example, 47 out of 60 displays as 78.3333%. Round the figure yourself if your report needs two decimals.
How do I find what percent X is of Y?
Use the second panel: enter X as the Part and Y as the Whole. The formula is (Part ÷ Whole) × 100. For example, 47 ÷ 60 × 100 = 78.3333%.
What happens if I enter zero as the whole or original value?
Dividing by zero has no meaningful answer, so the result shows a dash and a message asking for a non-zero Whole or Original value.
What is percent error and how do I calculate it?
Percent error measures how far a measured value is from the true value: (|measured − true| / |true|) × 100. Enter the true value as the Original value and the measured value as the New value in the third panel; the number shown is already the absolute percentage.

Explore the category

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Glossary

Percent
A ratio expressed as a fraction of 100, denoted by the % symbol. 'Per cent' literally means 'per hundred', so 25% means 25 out of every 100 units.
Percentage Point
The arithmetic difference between two percentage values. If unemployment rises from 4% to 6%, it increases by 2 percentage points — not by 2% (which would mean 2% of 4%, equalling 0.08%).
Base Value
The reference quantity from which a percentage is calculated. In 'what is 20% of $50', the base value is $50. Choosing the wrong base is the most common cause of percentage errors.
Percent Change
A measure of how much a value has grown or shrunk relative to its starting point, calculated as ((new − old) / old) × 100. A positive result is an increase; a negative result is a decrease.
Markup
The percentage added to a cost price to arrive at a selling price, calculated as (profit ÷ cost) × 100. A markup of 25% on a $100 item produces a $125 selling price.
Markdown
The percentage reduction applied to a price, typically to clear inventory or run a promotion. A 20% markdown on $125 reduces the price to $100 — the inverse of a 25% markup in this example.
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