Percentage Calculator | What Is X% of Y & More

Quick Start Guide

  1. Select a calculation mode: Choose from 7 percentage modes, or skip straight to the natural-language question box below the fields for a plain-English question.
  2. Enter your values: Fill in the fields your chosen mode asks for.
  3. View your result: The result updates automatically as you type.
  4. Try other modes: Switch modes anytime to explore the same numbers a different way — for example, percent-of vs. percent-change.
  5. Reuse recent calculations: Click any saved calculation to reload it.
  6. Export or copy your result: Save as JSON (guests) or PDF/CSV (signed in), or copy a formatted summary.

Understanding Percentages

8 modes, one underlying idea

Every mode here is really the same relationship — part, whole, and percent — solved for a different unknown. "X% of Y" solves for the part; "X is what % of Y" solves for the percent; "Reverse Percent" solves for the whole given a part and its percent. Picking the right mode just means picking which of the three you already know.

Percent change vs. percent difference

Percent change (this calculator's "Increase/Decrease" mode) divides by the starting value, so it matters which number came first — going from 100 to 150 is +50%, but 150 back to 100 is −33.3%, not −50%. Percent difference (not the same calculation) instead divides by the average of the two numbers and is direction-agnostic. Mixing these up is a common source of wrong answers.

Simple / Practical

These two tabs don't change how anything is calculated — they just filter which of the 7 workflow modes are shown, from the 3 most common (Simple) up to reverse-percentage and compound-percentage (Practical). The natural-language question box below the fields works independently of both tabs and is always available.

What this calculator does not cover

This handles single-step percentage arithmetic — it does not compound percentages over multiple periods (see a savings or investment calculator for that) or convert between percentages and fractions. For fraction math, see the Fraction Calculator.

Features

7 Calculation Modes: Supports core percentage math plus an always-available natural-language question box.

Recent History: Tracks recent calculations within your session.

Quick Actions: Useful presets for tips, sales tax, and discounts.

Common Use Cases

Discount and Sale: calculate percentage discount on items, find the final price after discount, and compare sale prices.

Growth and Change: calculate percentage increase/decrease, analyze investment growth, and track performance changes.

Tip and Tax: calculate tip amount on bills, determine sales tax, and total cost with tax included.

Data Analysis: find percentage breakdowns, compare proportions, and support statistical reporting.

Frequently Asked Questions

Convert the percentage to a decimal (divide by 100) and multiply by Y. Example: 20% of 50 = 0.20 × 50 = 10.
Formula: ((New Value − Old Value) ÷ Old Value) × 100. A positive result is an increase; a negative result is a decrease. Note this divides by the starting value, so 100 to 150 (+50%) and 150 back to 100 (−33.3%) are not mirror images of each other.
Use 'Add X% to Y' or 'Subtract X% from Y' mode. Enter the percentage and the base number. For example, adding a 15% tip to a $100 bill gives $115. Formula: Number ± (Number × Percentage ÷ 100).
Use 'X is what % of Y?' mode and enter both numbers. For example, 25 is 25% of 100. Formula: (First Number ÷ Second Number) × 100.
Both tabs calculate the same way — they just filter which of the 7 workflow modes are shown, from the 3 most common (Simple) up to reverse-percentage and compound-percentage (Practical). The natural-language question box below the fields works independently of both tabs and is always available.
Yes — the calculator automatically saves your recent calculations for the session. Click any saved calculation to reload it, which is useful for repeated calculations or comparing different scenarios.

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