Question 1

How do I calculate a percentage of a number?

Accepted Answer

To find X% of Y, multiply Y by X and divide by 100. For example, 15% of 250 = 250 x 15 / 100 = 37.50. Our calculator does this instantly — just type the percentage and the number.

Question 2

How do I calculate the percentage change between two numbers?

Accepted Answer

Percentage change = ((New Value - Old Value) / Old Value) x 100. If a stock went from $80 to $120, the change is ((120-80)/80) x 100 = 50% increase. A positive result means increase, negative means decrease.

Question 3

How much should I tip at a restaurant?

Accepted Answer

In the US, 15-20% is standard. 15% for average service, 18% for good service, and 20%+ for excellent service. Our tip calculator splits the bill evenly between any number of people and can round up to the nearest dollar for convenience.

Question 4

What is the difference between profit margin and markup?

Accepted Answer

Margin is profit as a percentage of selling price: (Selling Price - Cost) / Selling Price x 100. Markup is profit as a percentage of cost: (Selling Price - Cost) / Cost x 100. A product bought for $50 and sold for $80 has a 37.5% margin but a 60% markup. Margin is always lower than markup for the same transaction.

Question 5

What is a good profit margin for my business?

Accepted Answer

It varies by industry. Grocery/retail averages 2-5%, restaurants 3-9%, professional services 15-25%, software/SaaS 70-90%. Generally, below 10% is considered low, 10-20% is average, 20-50% is good, and above 50% is excellent (common in digital products and software).

Percentage, Tip & Profit Calculator

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