semkuPercentage calculator

Percentage calculator

Choose the calculation you need. Each result shows the numbers used, the base and the formula.

What would you like to calculate?
Each calculation keeps its own inputs when you switch.
Find a percentage of the base value. For example, 20% of 200 is 40.
Results are displayed to the selected number of decimal places, including trailing zeros. The inputs and base are not rounded.
Use a decimal point or comma: 12.5 and 12,5 mean the same number. Negative values are allowed. Thousands separators are not supported. Enter one thousand as 1000. Because commas and full stops are read as decimal separators, both 1,000 and 1.000 are read as 1. A final % sign does not change the entered number. Use it for percentage inputs; enter base values, parts and totals as numbers.
Result
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Enter both values to see the result.
 A change from 20% to 25% is 5 percentage points and a 25% relative increase.
The copy includes your inputs, the base, the formula and the result. Copied text may remain on your clipboard. This calculator provides arithmetic results, not financial or tax advice. The selected decimal places affect the displayed result only. Calculations use the full input values.
Calculation rules and supported formats

To find X% of Y, calculate X ÷ 100 × Y. The result is an amount, not another percentage. For example, 20 ÷ 100 × 200 = 40.

To find what percentage a part is of a whole, calculate part ÷ whole × 100. For example, 18 ÷ 24 × 100 = 75%. The whole cannot be zero. If the whole is negative, its sign stays in the denominator.

For percentage change, calculate (new value − starting value) ÷ abs(starting value) × 100. Here, abs means absolute value: abs(−80) is 80. A change from 80 to 100 is +25%; a change from 100 to 80 is −20%. The starting value cannot be zero. For a negative starting value, this calculator uses its absolute value as the base. This convention is stated with the result.

To compare two percentages, subtract the starting percentage from the new percentage. The difference is measured in percentage points. Relative percentage change is (new percentage − starting percentage) ÷ abs(starting percentage) × 100, using the numbers as entered: use 20 for 20%. From 20% to 25%, the difference is 5 percentage points and the relative change is +25%. If the starting percentage is zero, only the percentage-point change is defined.

Increase, decrease and no change describe the exact numerical comparison before rounding. They do not say whether a change is favourable. A small increase may be displayed as 0% after rounding and still be labelled Increase.

Calculations use the full input values without intermediate rounding. Each displayed result is rounded separately to the selected decimal places. Ties are rounded away from zero: 0.005 becomes 0.01 and −0.005 becomes −0.01 to two decimal places. Trailing zeros are kept. No rounding needed describes the displayed number only. The ≈ symbol marks an approximate result.

Enter whole numbers or decimals, with an optional sign. Use one decimal point or comma. Thousands separators, fractions and scientific notation are not supported as inputs. A final % sign is ignored when the number is read; 20% is read as 20, not 0.2. The whole-number part can contain up to 15 digits. Results use a decimal point and no thousands separators.

Calculation rules v1 · 14 September 2026

Frequently asked questions
What is the formula for a percentage?
To express a part as a percentage of a whole, divide the part by the whole and multiply by 100. For example, 18 out of 24 is 18 ÷ 24 × 100 = 75%. The whole cannot be zero.
How do I calculate a percentage of a number?
Divide the percentage by 100, then multiply by the number. For example, 20% of 200 is 20 ÷ 100 × 200 = 40. Choose X% of Y and enter 20 and 200.
How do I calculate a percentage increase or decrease?
Choose Percentage change from A to B. With a positive starting value, subtract it from the new value, divide by the starting value and multiply by 100. From 80 to 100, the increase is 25%. From 100 to 80, the decrease is 20%. For a negative starting value, this calculator uses its absolute value as the denominator and shows a note.
How do I calculate a percentage from marks?
Choose X is what % of Y. Enter the marks earned as the part and the total possible marks as the whole. For example, 18 out of 24 is 75%. This calculates the percentage only; it does not apply grade boundaries or weighting.
Is percentage difference the same as percentage change?
Percentage difference often uses the average of two positive values as its base. Percentage change uses a starting value. This calculator uses a starting value for change and shows percentage points separately when comparing two rates. A move from 20% to 25% is 5 percentage points and a 25% relative increase. It does not calculate difference using the average of two values.
How do I calculate a discount?
Use X% of Y to find the discount amount, with the discount percentage as X and the original price as Y. Then subtract the result from the original price. For example, 20% of 200 is 40, so the price after that discount is 160. The calculator returns the discount amount in this mode.

Privacy on this page

This page does not send usage statistics or automatic error reports and does not provide a feedback form. Calculations run in your browser. semku does not send your calculation inputs or results to the server or save them permanently in browser storage. Separately, the hosting provider Cloudflare processes access data in standard access logs when you visit the website. Hosting through Cloudflare Pages generates records that include your IP address, the time of the request and user-agent information. More information is available in the privacy policy in Korean.