Percent of Number Calculator

Mode

Pick the question you want answered.

Precision (decimals)

Higher precision keeps more decimal digits.

Rounding

Controls how values are rounded.

Percent (%)

Number

Part

Whole

Known result

Percent (%)

Starting number

Change percent (%)

Direction

Reset

Formula used

Percent of number: result = (p ÷ 100) × n
What percent: p = (part ÷ whole) × 100
Base from percent: base = (result × 100) ÷ p
Increase or decrease: new = n × (1 ± p ÷ 100)

How to use this calculator

Select the mode that matches your question.
Enter the required values in the visible fields.
Set precision and rounding if you need control.
Press Calculate to see results above the form.
Use the export buttons to save CSV or PDF.

Example data table

Mode	Input	Input	Output
Percent of a number	15%	260	39
What percent?	30	120	25%
Base from percent	45	12.5%	360
Increase or decrease	200	8% increase	216

Examples are rounded for readability.

FAQs

1) Can I use negative percentages?

Yes. A negative percent flips the direction in percent-of-number mode, and it can represent losses or offsets. For change mode, use the direction selector plus a positive percent for clarity.

2) Why does my result look slightly different from a calculator?

Differences usually come from rounding choices and displayed precision. Increase the precision setting, or switch rounding to floor or ceil. The steps show raw and rounded values.

3) What does “Base from percent” mean?

It solves the reverse problem: if you know a value is p% of some base, it finds that base. Example: 45 is 12.5% of 360.

4) Can I calculate a discount or tax?

Yes. Use “Percent of a number” to find the discount amount, then subtract it. Or use “Increase or decrease” to apply tax or markdown directly as a new value.

5) What happens if I enter whole as zero?

Percent as a ratio requires dividing by the whole. Division by zero is undefined, so the calculator blocks that input and asks you to change it.

6) Does the export include my steps?

Exports include the mode, inputs, the main result, and notes about rounding. Steps are shown on-screen for quick review and learning.

7) Which rounding should I choose?

Half up matches many handheld calculators. Floor always rounds down, while ceil always rounds up. For money, choose the method your policy requires.

8) Is this tool suitable for large numbers?

It works well for typical business and study values. Extremely large inputs may lose precision due to floating point limits, so consider using fewer digits or scaling units.