How to use the Percentage Calculator
This calculator covers four common percentage tasks in one place: finding a percentage of a number, finding what percentage one number is of another, measuring percentage increase or decrease, and calculating a discounted final price. Start by choosing the mode that matches your question. The field labels, formula breakdown, and result description then update to match that calculation.
As you change the values, the result can update immediately. If you also press Calculate, the same calculation is confirmed with a brief visual loading cue before the result is shown. The answer card gives the result, while the formula card shows the expression used so you can check the arithmetic.
1. Find a percentage of a number
Choose Percentage of a number when your question is like “What is 20% of 200?” Enter the percentage first and the number second. The formula is (percentage ÷ 100) × number. For 20% of 200, the calculation is (20 ÷ 100) × 200 = 40.
The result is the percentage portion itself. If you need the amount left after removing a percentage, use Discount & final price instead.
2. Find what percentage one number is of another
Choose Percentage ratio when you know a part and a whole and want the percentage. Enter the part as X and the whole as Y. The formula is (X ÷ Y) × 100. For example, 30 out of 120 is 25%.
The whole value cannot be zero because division by zero is undefined. If the second value is zero, the calculator keeps the previous valid result and reports the input problem instead of presenting a misleading answer.
3. Calculate percentage increase or decrease
Choose Increase / decrease. Enter the original value first and the new value second. The tool uses ((new − original) ÷ |original|) × 100. A move from 80 to 100 is a 25% increase, while a move from 100 to 80 is a 20% decrease.
The original value cannot be zero. For negative starting values, this calculator divides by the magnitude of the original value, so interpret the result in the context of the values you are comparing.
4. Calculate a discount and final price
Choose Discount & final price. Enter the discount percentage and the original price. The formula is original price − ((discount ÷ 100) × original price). A 20% discount on 200 gives a final price of 160.
For an ordinary discount, use a percentage from 0% to 100%. The calculator can process other numeric values, but percentages outside that range may represent a surcharge or produce a result that does not make sense as a normal retail price.
Quick picks, result actions, and the visual bar
The quick-pick buttons enter common values such as 5%, 10%, 15%, 18%, 20%, and 50%. The 18% GST chip only enters the number 18; it does not decide whether tax should be added, removed, or treated as inclusive. Choose the calculation mode that matches the tax question you actually need to solve.
Copy Result copies the current calculation result. Share opens the device share sheet when supported and otherwise copies shareable text. Reset returns the calculator to the default 20% of 200 example. The progress bar is a visual aid: in percentage and discount modes it shows the selected percentage, while in percentage-change mode it shows the magnitude of the change.
Check inputs and interpret the answer
- Choose the calculation mode that matches the question you are solving.
- Read the field labels and enter the values in the displayed order.
- Use a quick-pick button when one of the preset values is convenient.
- Review the answer card and formula breakdown to confirm the calculation.
- Copy, share, or reset the result when you are finished.
Accuracy, rounding, and input limits
The arithmetic runs in your browser and results are formatted to a maximum of twelve significant digits. Inputs are limited to magnitudes of one trillion. Like most browser calculators, very small decimal fractions can be affected by standard floating-point representation, so this tool is intended for practical everyday calculations rather than arbitrary-precision mathematics.
For money, invoices, tax, or accounting, apply the rounding rule required by the relevant store, payment system, tax authority, or accounting standard. A mathematically correct percentage can still differ from an official total if another system rounds intermediate values differently.
What the calculator does with your values
The percentage arithmetic is performed in the browser, and this tool does not create a calculation-history list. Reset clears the current fields back to their defaults. Copy and Share only act when you choose those controls.
Percentage points are different from percent change
If a rate moves from 10% to 12%, it rises by 2 percentage points. Relative percent change compares the difference with the starting value, so the same move is a 20% increase. Keeping those two ideas separate prevents a common interpretation error.
Frequently asked questions
What is a percentage and how is it calculated?
A percentage expresses a quantity per 100. To find P% of a number N, divide P by 100 and multiply by N.
How do I calculate a percentage of a number?
Choose Percentage of a number, enter the percentage first and the number second, then review the live result or press Calculate. For example, 25% of 80 is 20.
How do I find what percentage one number is of another?
Use Percentage ratio. Divide the first number by the second and multiply by 100. For example, 30 out of 120 is 25%.
How is percentage increase or decrease calculated?
Subtract the original value from the new value, divide by the magnitude of the original value, and multiply by 100. A positive result is an increase and a negative result is a decrease.
How do I calculate a discount and final price?
Choose Discount & final price, enter the discount percentage and original price, and calculate. The tool subtracts the percentage discount from the original price.
Can I enter decimal percentages such as 7.5%?
Yes. Decimal percentages and decimal numbers are supported, so values such as 7.5%, 12.25%, or 99.9 can be entered directly.
Is a percentage point the same as a percent change?
No. A move from 10% to 12% is two percentage points, while the relative percent change is 20%.
Why can’t ratio or percentage change divide by zero?
Those calculations require division by the whole or original value. A denominator of zero makes the percentage mathematically undefined.
What does the 18% GST quick pick do?
It enters 18 as the current percentage value. It does not automatically add or remove tax, so choose the calculation mode that matches the GST calculation you need.
Does the percentage calculator save my values or results?
The tool does not create a calculation-history list. The arithmetic runs in the browser, and Reset restores the default calculator values.