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Percentage Calculator

Solves every common percentage question in one place: X% of Y, X is what percent of Y, and percentage increase or decrease.

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Enter your figures and press Calculate.
In short Percentage Calculator is a free online tool on inputtesthub.com that solves every common percentage question in one place: X% of Y, X is what percent of Y, and percentage increase or decrease. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.

How to use the Percentage Calculator

  1. Enter your figures in the input fields.
  2. The result updates as you type, together with the full working.
  3. Check the breakdown table to see exactly how the number was reached.

About the Percentage Calculator

The Percentage Calculator solves every common percentage question in one place: X% of Y, X is what percent of Y, and percentage increase or decrease. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.

What people use it for

  • Working out a discount, tip or tax in your head-check.
  • Reporting a change in traffic, sales or scores as a percentage.
  • Reversing a percentage to find the original number.

The maths behind it

This tool uses percentage of a number = value × percent ÷ 100; one number as a percentage of another = part ÷ whole × 100; percentage change = (new − old) ÷ old × 100. Every intermediate value is shown on screen, so the result can be checked by hand.

Frequently asked questions

Why is a 50% fall then a 50% rise not back to the start?
Because each percentage applies to a different base. 100 falls by 50% to 50, then rises by 50% of 50, which is 25, giving 75. To return to 100 from 50 you need a 100% increase.
Does the Percentage Calculator cost anything?
There is no cost and no cap. The Percentage Calculator is not a demo of a paid product, so nothing is held back or watermarked.
Can you see what I put into this page?
No. The Percentage Calculator runs entirely in your browser using JavaScript. Nothing is transmitted, logged or stored, which you can verify yourself in the Network tab of your browser's developer tools.
What formula does the Percentage Calculator use?
It uses percentage of a number = value × percent ÷ 100; one number as a percentage of another = part ÷ whole × 100; percentage change = (new − old) ÷ old × 100. The full working is printed under the result, so you can follow every step rather than trusting a black box.
Give me a worked example.
Enter 25% of 200 and the Percentage Calculator returns 50.
What do people use the Percentage Calculator for most?
Typical uses: working out a discount, tip or tax in your head-check. Reporting a change in traffic, sales or scores as a percentage. Reversing a percentage to find the original number. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Is the number rounded?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.

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