Percentage Calculator
Use any of the tools below to calculate percentages, percent increase/decrease, and percentage change quickly.
1) Find X% of Y
2) What % is A of B?
3) Increase or Decrease by %
4) Percent Change (Old → New)
Why use a calculator with percentage?
Percentages are part of everyday decisions: discounts while shopping, savings goals, tax rates, investment returns, grade calculations, and business performance reports. A calculator with percentage saves time and reduces errors by applying the formulas for you instantly.
Instead of doing multiple steps manually, you can enter your values and get clear results. This is especially useful when you are comparing options quickly, such as determining whether a 25% discount on one item is better than a 15% discount on another item with a lower base price.
Core percentage formulas (quick reference)
1) Find a percentage of a number
Formula: Result = (Percentage ÷ 100) × Number
Example: 20% of 150 = (20 ÷ 100) × 150 = 30
2) Find what percent one number is of another
Formula: Percentage = (Part ÷ Whole) × 100
Example: 30 is what percent of 120? (30 ÷ 120) × 100 = 25%
3) Increase or decrease a value by a percentage
Increase: New Value = Original × (1 + Percentage ÷ 100)
Decrease: New Value = Original × (1 - Percentage ÷ 100)
Example: Increase 800 by 12% → 800 × 1.12 = 896
4) Calculate percent change between old and new values
Formula: Percent Change = ((New - Old) ÷ Old) × 100
Example: Old = 50, New = 65 → ((65 - 50) ÷ 50) × 100 = 30% increase
Practical examples you can solve with this tool
- Shopping: Find the final price after a sale discount.
- Personal finance: Calculate salary raise percentages or budget cuts.
- Investing: Estimate gain/loss percentages on stocks or funds.
- School: Compute test score percentages and grade improvements.
- Business: Track month-over-month growth in revenue or users.
Common mistakes to avoid
- Confusing “percent of” with “percent change.” These are different calculations.
- Using the wrong base number when comparing two values.
- Forgetting that a negative result means a decrease.
- Attempting percent change from an old value of zero, which is mathematically undefined.
Tips for better percentage calculations
Always identify the base value first. If you are calculating a discount, the base is the original price. If you are calculating growth, the base is the old value. In reports and dashboards, consistent base values are key to making valid comparisons over time.
For financial decisions, round only at the final step to avoid compounding rounding errors. This calculator keeps decimals until the end so you can get more accurate outputs.
Frequently asked questions
Is this percentage calculator free to use?
Yes. It runs directly in your browser and does not require sign-up.
Can I use decimal percentages like 2.75%?
Absolutely. The calculator accepts both whole numbers and decimal percentages.
What if my values are negative?
Negative values are supported for many cases. Just interpret the result carefully in context, especially with percent change and directional comparisons.
Final thought
A reliable calculator with percentage is one of the most practical tools you can keep handy. Whether you're managing money, evaluating performance, or checking quick math on the go, clear percentage calculations help you make better decisions faster.