Percentage Calculator
Use any section below. You can type whole numbers or decimals.
1) What is X% of Y?
2) A is what percent of B?
3) Percent change (increase or decrease)
Quick Answer
If you are asking, “How do I figure percentage on a calculator?” the shortest answer is this: divide, then multiply by 100.
- Find X% of Y:
(X ÷ 100) × Y - Find what percent A is of B:
(A ÷ B) × 100 - Find percent increase/decrease:
((New - Old) ÷ Old) × 100
That’s the core idea. Once you understand those three formulas, you can solve almost every percentage problem: discounts, tax, tips, test scores, savings growth, and budget tracking.
How to Do Percentages on a Basic Calculator
Method 1: Without the % button
Even the most basic calculator can do percentages if it has divide and multiply. For example, to find 18% of 250:
- Type 18 ÷ 100 (which gives 0.18)
- Then multiply by 250
- Answer: 45
So, 18% of 250 is 45.
Method 2: Using the % key
Many phone and handheld calculators include a percent key. A common flow is: number × percent %. For example, for 15% of 80:
- Type 80 × 15 %
- Result: 12
Different calculator brands may handle the % key slightly differently, so if results look odd, use Method 1 and the formula approach. It always works.
Practical Examples You’ll Use in Real Life
Shopping discount
A jacket costs $120 and is 25% off.
- Discount amount:
25% of 120 = 30 - Final price:
120 - 30 = 90
Restaurant tip
Your bill is $48 and you want to leave 20%.
- Tip:
20% of 48 = 9.60 - Total:
48 + 9.60 = 57.60
Sales tax
Item price is $75 and tax is 8%.
- Tax:
8% of 75 = 6 - Total:
75 + 6 = 81
Test score percentage
You got 42 correct out of 50.
(42 ÷ 50) × 100 = 84%
How to Calculate Percentage Increase and Decrease
This one is especially useful for budgeting, salary changes, and price comparisons.
Formula: ((New - Old) ÷ Old) × 100
Example: price goes from 40 to 50.
- Change:
50 - 40 = 10 - Relative change:
10 ÷ 40 = 0.25 - Percent change:
0.25 × 100 = 25%
That means a 25% increase.
Common Percentage Mistakes
- Forgetting to divide by 100: 15% means 0.15, not 15.
- Using the wrong base value: “percent of what?” matters.
- Mixing up increase vs. final amount: 10% increase means add 10% to the original, not replace it.
- Confusing percentage points with percent change: moving from 10% to 15% is +5 percentage points, but +50% relative change.
Fast Mental Shortcuts
- 10% = move decimal one place left (10% of 250 = 25)
- 5% = half of 10% (5% of 250 = 12.5)
- 1% = move decimal two places left (1% of 250 = 2.5)
- 15% = 10% + 5%
- 20% = 10% × 2
Final Takeaway
To figure percentage on a calculator, remember one rule: percent problems are just division and multiplication. Use the calculator above whenever you need a quick answer for discounts, tips, grades, taxes, or percent change.