MT
My Toolbox

Percentage Calculator — Calculate Percentages, Increases & Decreases

What's 15% of 230? What percentage is 45 of 180? How much is a 20% discount on $89? Type the numbers, get the answer. Handles all three common percentage questions in one tool.

Quickly calculate percentages

Calculate
Calculate percentages and percentage changes
Result
Calculate percentages and percentage changes
Enter value

Three Types of Percentage Problems

Every percentage question falls into one of three patterns:

1. "What is X% of Y?" — Multiply: Y × (X/100). Example: 15% of 230 = 230 × 0.15 = 34.5

2. "X is what percent of Y?" — Divide: (X/Y) × 100. Example: 45 is what % of 180? = (45/180) × 100 = 25%

3. "What is Y after X% increase/decrease?" — Add/subtract: Y × (1 + X/100) for increase, Y × (1 - X/100) for decrease. Example: $89 after 20% discount = 89 × 0.80 = $71.20

The confusion people have: "percentage" vs "percentage points." If a tax rate goes from 10% to 12%, that's a 2 percentage point increase but a 20% relative increase (2/10 = 0.20). Politicians and media often mix these up — "taxes increased by 2%" could mean either thing. This calculator works with relative percentages (the mathematical kind).

How to Use

  1. Enter the base value (the number you're calculating a percentage of).
  2. Enter the percentage (positive for increase, negative for decrease).
  3. See the percentage amount and the final total instantly.
  4. Use negative percentages for discounts and decreases.

When You'll Use This

Calculating discounts while shopping

Item is $89 with a 30% off sale. What's the final price? 89 × 0.70 = $62.30. Or: what's the actual savings? 89 × 0.30 = $26.70 off. Quick math before deciding if the "deal" is worth it.

Figuring out tips at restaurants

Bill is $67. 15% tip = $10.05. 18% = $12.06. 20% = $13.40. Quick trick: 10% of $67 is $6.70, double it for 20% ($13.40), or add half for 15% ($10.05).

Understanding salary increases or tax rates

You got a 4% raise on a $75,000 salary. That's $3,000 more per year, or $250/month before tax. Is it worth celebrating? Depends on inflation — if inflation is 3.5%, your real raise is only 0.5%.

Calculating margins and markups in business

You buy a product for $40 and sell for $60. Markup is 50% (20/40). But margin is 33% (20/60). These are different calculations that confuse many business owners. Markup is based on cost, margin is based on selling price.

Common Mistakes

1.

Percentage increase then decrease doesn't return to original

A 20% increase followed by a 20% decrease does NOT give you the original number. $100 + 20% = $120. $120 - 20% = $96 (not $100). The second 20% is calculated on the larger number. This is why stock markets need a 25% gain to recover from a 20% loss.

2.

Percentage points ≠ percentage

Interest rate going from 3% to 4% is a 1 percentage point increase but a 33% relative increase. "Sales grew by 5%" and "market share grew by 5 percentage points" mean very different things. Always clarify which is meant.

3.

Margin vs markup — know which you're calculating

Markup = (profit / cost) × 100. Margin = (profit / revenue) × 100. A 50% markup ($40 cost → $60 price) is only a 33% margin. If someone says "we need 40% margin," don't apply a 40% markup — you'll underprice.

4.

Compounding percentages multiply, they don't add

Three consecutive 10% increases is not 30%. It's 1.10 × 1.10 × 1.10 = 1.331, or 33.1%. The difference grows with larger percentages and more periods. This is why compound interest is more powerful than it seems.

Examples

25% discount on $89

A common shopping calculation — what do you actually pay?

Input

Base: $89 | Percentage: -25%

Output

Discount: $22.25 | Final price: $66.75

What percentage is 45 of 180?

Finding what fraction one number is of another.

Input

45 ÷ 180 × 100

Output

25%

Features

  • Calculates percentage of any number instantly
  • Shows both the percentage amount and the total after applying
  • Supports negative percentages for discounts/decreases
  • Handles decimal percentages (7.5%, 2.25%, etc.)
  • Visual indicators for increases vs decreases
  • Runs 100% in your browser — no data sent anywhere

Frequently Asked Questions

How do I calculate X% of a number?

Multiply the number by X/100. 15% of 230 = 230 × 0.15 = 34.5. Quick mental math: 10% is just moving the decimal (230 → 23), then adjust. 15% = 10% + 5% = 23 + 11.5 = 34.5.

How do I find what percentage one number is of another?

Divide the part by the whole, multiply by 100. "45 is what % of 180?" = (45 ÷ 180) × 100 = 25%. Think of it as: what fraction is 45 of 180? It's 1/4, which is 25%.

Why doesn't a 20% increase then 20% decrease give me the original?

Because the decrease is calculated on the increased amount. $100 + 20% = $120. Then $120 - 20% = $120 × 0.80 = $96. The 20% decrease is 20% of $120 ($24), not 20% of the original $100 ($20). To get back to $100 from $120, you need a 16.67% decrease (20/120).

What's the difference between markup and margin?

Markup is profit as a percentage of COST: (60-40)/40 = 50% markup. Margin is profit as a percentage of REVENUE: (60-40)/60 = 33% margin. Same transaction, different percentages. Retail typically talks margin; wholesale talks markup. A 100% markup = 50% margin.

How do I calculate percentage change between two numbers?

Formula: ((new - old) / old) × 100. Revenue went from $80K to $95K: ((95-80)/80) × 100 = 18.75% increase. If it went from $95K to $80K: ((80-95)/95) × 100 = -15.8% decrease. Note: the percentage is different depending on direction.

Tips & Related Workflows