How to use this calculator
Enter the part you want to describe and the whole it is compared with. Divide the part by the whole, then multiply by 100. The order matters: 20 out of 80 is not the same percentage as 80 out of 20. Keep units consistent, such as points out of points or one currency amount out of another.
Formula
Part ÷ Whole × 100
Worked example
30 out of 200 gives 30 ÷ 200 × 100 = 15%. The ratio is 0.15 and the remaining amount is 170. A part of 250 out of 200 gives 125%.
Assumptions and limitations
The whole must not be zero. A zero part with a nonzero whole is 0%, but zero divided by zero is undefined. Signed values are supported mathematically; negative totals may be hard to interpret as a real-world share.
Frequently asked questions
Is this the same as percentage change?
No. This tool uses part ÷ whole. Percentage change first subtracts the original value from the new value, then divides by the original. Use the change tool for growth or decline.
How precise are these results?
Calculations use ordinary floating-point arithmetic. Results show up to six decimal places; very small nonzero values use scientific notation. They are estimates for everyday arithmetic, not arbitrary-precision accounting.
Can I use decimals and negative numbers?
Yes where the input allows them. Percentage change requires a nonnegative starting value; difference uses nonnegative values; discount requires a nonnegative price and a rate between 0% and 100%.
Keep the same units for both values. Amounts have no assumed currency.