Percentage Calculator
Use these quick tools to calculate percentages, discounts, tips, tax, and percent change in seconds.
1) Find X% of Y
2) What percent is A of B?
3) Increase or Decrease by %
Tip: For a 20% discount, use Decrease and enter 20.
The fast answer
If you are asking, “how do you calculate a percentage on a calculator,” the core idea is simple:
- To find a percentage of a number: (percent ÷ 100) × number
- To find what percent one number is of another: (part ÷ whole) × 100
- To add a percentage increase: number × (1 + percent ÷ 100)
- To subtract a percentage decrease: number × (1 - percent ÷ 100)
How to do it on a basic calculator
Method A: With a % button
Many calculators (especially phone calculators) let you use the % key directly. For example, to find 15% of 240:
- Type 240 × 15 %
- Press equals
- You get 36
For discounts, you can do: original - (original × discount%), or on some devices: original - discount% after typing the original value first.
Method B: Without a % button
If your calculator has no percent key, just convert the percent to decimal by dividing by 100.
- 15% becomes 0.15
- 7.5% becomes 0.075
- 125% becomes 1.25
Then multiply by the number you care about.
Everyday examples
1) Sales discount
A jacket costs $120 and is 25% off.
- Discount amount: 120 × 0.25 = 30
- Final price: 120 - 30 = 90
2) Restaurant tip
Your meal is $48 and you want to leave an 18% tip.
- Tip: 48 × 0.18 = 8.64
- Total: 48 + 8.64 = 56.64
3) Tax
An item costs $85 and tax is 7%.
- Tax: 85 × 0.07 = 5.95
- Total with tax: 85 + 5.95 = 90.95
4) Percent increase
Your salary is $60,000 and increases by 4%.
- Increase amount: 60,000 × 0.04 = 2,400
- New salary: 62,400
Common mistakes to avoid
- Forgetting to divide by 100: 12% is 0.12, not 12.
- Using the wrong base number: always verify what the percent applies to.
- Confusing percentage points vs percent change: going from 10% to 12% is a 2 percentage-point increase, not 2% increase.
- Rounding too early: keep full decimals until the final step for better accuracy.
Mental shortcuts that save time
- 10% is easy: move decimal one place left (10% of 250 = 25).
- 5% is half of 10% (5% of 250 = 12.5).
- 1% is move decimal two places left (1% of 250 = 2.5).
- 15% = 10% + 5%.
- 20% = double 10%.
Quick reference formulas
Find percentage of a number
Result = (P ÷ 100) × N
Find what percent A is of B
Result = (A ÷ B) × 100
Increase by a percentage
New value = Original × (1 + P ÷ 100)
Decrease by a percentage
New value = Original × (1 - P ÷ 100)
Final takeaway
Once you remember that “percent” means “per 100,” percentage math becomes straightforward. Whether you are calculating discounts, tips, tax, markups, or growth, the same handful of formulas works every time. Use the calculator above to get instant answers and verify your manual calculations.