Percentage Calculator

What this tool does

This percentage calculator handles three modes: a specified percentage of a value, one value as a percentage of a total, and percentage increase or decrease from an initial value to a final value. Decimal and negative numbers work where the selected formula permits, and results update immediately. It does not provide dedicated discount, tax, tip, markup, margin or compound-growth workflows, reverse percentage or original-value recovery, financial, tax or accounting advice, saved history, spreadsheets or batch calculations. Inputs and results stay in the browser and are not uploaded to LocalTools.

How to use it

1. Choose percent of a value, share of a total or percentage change.
2. Enter the two numbers required by that formula, including decimals or negatives where valid.
3. Read the result immediately; the calculation remains in your browser.

Privacy

This tool runs entirely in your browser. Your input is never uploaded, stored or shared — closing the tab removes it.

Frequently asked questions

How do you calculate a percentage of a number?

To find P% of a value, multiply the value by P and divide by 100, or enter both numbers in the percent-of-value mode.

How do you calculate what percentage one number is of another?

Divide the part by the total and multiply by 100%. The formula is undefined when the total is zero.

What is the formula for percentage change?

Subtract the initial value from the final value, divide by the initial value, then multiply by 100%. A positive result is an increase and a negative result a decrease; the initial value cannot be zero.

Can this recover an original value or calculate a discount?

No. There is no reverse-percentage or original-value mode and no dedicated discount, tax, tip, markup, margin or compound-growth workflow.

Are my numbers sent to a server?

No. The calculation runs immediately in your browser, and LocalTools does not receive the input or result.