How to Use Percentage Calculator
The Percentage Calculator is a multi-mode tool designed for fast, accurate percentage math with no manual formula entry required.
- Select a mode — Choose from four calculation modes at the top of the Percentage Calculator: "What % is A of B?", "What is X% of B?", "% Change", or "Increase / Decrease by %".
- Enter your values — Fill in the number fields shown for that mode. The Percentage Calculator accepts any real number.
- Read the result — The Percentage Calculator instantly displays the answer in the result panel on the right. For percent change, a color-coded badge shows whether the value increased or decreased.
The Percentage Calculator updates in real time — there is no submit button to press. Switch modes freely to explore different percentage relationships in the same data.
Formula & Theory — Percentage Calculator
The Percentage Calculator is built on four core percentage formulas that cover the most common real-world scenarios.
What percent is A of B?
Percentage = (A ÷ B) × 100
What is X% of B?
Result = (X ÷ 100) × B
Percent change from original to new value:
Percent Change = ((New − Original) ÷ |Original|) × 100
Adjust a value by a percentage:
Result = Base × (1 + X/100) [increase]
Result = Base × (1 − X/100) [decrease]
| Symbol | Meaning |
|---|---|
| A | Part value |
| B | Total or reference value |
| X | Percentage rate |
| Original | Starting value for change calculation |
| New | Ending value for change calculation |
The Percentage Calculator evaluates these formulas client-side so results appear instantly as you type.
Use Cases for Percentage Calculator
The Percentage Calculator handles a broad range of everyday and professional scenarios:
- Retail discounts — Enter the original price and discount rate to find the sale price using the Increase / Decrease by % mode.
- Grade and score analysis — Use the "What % is A of B?" mode to find what percentage of total marks a student earned.
- Financial growth — Track investment returns or salary increases with the % Change mode of the Percentage Calculator.
- Tip calculation — Find 15% or 20% of any bill amount with the "What is X% of B?" mode.
- Data comparison — Quickly see how two figures relate as a percentage when analyzing reports or surveys.
- Tax and surcharge — Apply a tax rate to a base price using the Increase by % option in the Percentage Calculator.
Whether you need a quick mental math check or a precise figure for a report, the Percentage Calculator handles it in seconds.