Percentage Calculator
The universal tool for proportional math and growth analysis.
Percent Calculator
Percentages show up everywhere — sales discounts, tip calculations, grade percentages, interest rates, and data analysis. This calculator handles every type of percentage question in one place.
Three Types of Percentage Problems
- What is X% of Y? → e.g., What is 15% of $80? = $12
- X is what % of Y? → e.g., 45 is what % of 180? = 25%
- X is Y% of what? → e.g., 36 is 40% of what? = 90
How to Use This Calculator
- Select the type of percentage problem you want to solve.
- Enter the known values.
- Click Calculate for the instant answer.
Key Percentage Formulas
P% of X = (P ÷ 100) × X
X is what % of Y = (X ÷ Y) × 100
Percentage change = ((New − Old) ÷ Old) × 100
Find original (X is Y% of ___) = X ÷ (Y ÷ 100)
Example Calculations
- 15% of $240 = $240 × 0.15 = $36
- 75 out of 300 = 75 ÷ 300 × 100 = 25%
- Price went from $50 to $65 → change = (65−50)/50 × 100 = +30%
- After 20% increase, price is $120. Original = $120 ÷ 1.20 = $100
Common Mistakes to Avoid
- Adding percentages directly — A 25% increase followed by a 25% decrease doesn't return to the original. $100 +25% = $125, then −25% = $93.75 (not $100).
- Confusing percent change direction — Use the original value as the denominator, not the new value.
- Percent points vs. percent — Going from 10% to 15% is a 5 percentage-point increase but a 50% relative increase. These are different concepts.
Frequently Asked Questions
How do I calculate a tip?
Multiply the bill by the tip percentage: $85 bill × 20% tip = $17 tip → $102 total. For a quick 20% estimate: move the decimal one place ($8.50) and double it ($17). See our Tip Calculator.
What is a percentage point?
A percentage point is the arithmetic difference between two percentages. If interest rates go from 3% to 5%, that's a 2 percentage-point increase (but a 67% relative increase).
How do I calculate percentage off?
Sale price = Original × (1 − Discount%). A 35% discount on $200: $200 × 0.65 = $130. See our Discount Calculator for more.
Conclusion
Whether you're checking a sale price, calculating a grade, or analyzing data, percentages are unavoidable. This calculator makes any percentage problem trivial — choose the question type, enter your numbers, and get the answer instantly.
Related: Discount Calculator | Tip Calculator | Fraction Calculator | Percent Error Calculator
Expert Math
Percentages are reversible. X% of Y is always equal to Y% of X. For example, 8% of 50 is the same as 50% of 8 (which is 4). This can often make mental math much easier!
