How to Work Percentage Without Calculator

Basic Percentage Calculation

To calculate a percentage of a number without a calculator, follow these steps:

1. Write down the percentage you want to calculate (e.g., 20%).
2. Convert the percentage to a decimal by dividing by 100 (20% = 0.20).
3. Multiply the decimal by the number you want to find the percentage of.

Example: What is 25% of 80?

1. Convert 25% to decimal: 0.25
2. Multiply by 80: 0.25 × 80 = 20
3. Answer: 25% of 80 is 20

Calculating Percentage Increase

To find the percentage increase between two numbers:

1. Subtract the original number from the new number.
2. Divide the result by the original number.
3. Multiply by 100 to get the percentage.

Example: If a product's price increases from $50 to $75, what is the percentage increase?

1. Subtract: 75 - 50 = 25
2. Divide: 25 / 50 = 0.5
3. Multiply: 0.5 × 100 = 50%
4. Answer: The price increased by 50%

Calculating Percentage Decrease

The process for percentage decrease is similar to increase, but you'll get a negative result.

Example: If a stock drops from $100 to $80, what is the percentage decrease?

1. Subtract: 100 - 80 = 20
2. Divide: 20 / 100 = 0.2
3. Multiply: 0.2 × 100 = 20%
4. Answer: The stock decreased by 20%

Finding Percentage of Total

To find what percentage one number is of another:

1. Divide the part by the whole.
2. Multiply by 100 to convert to percentage.

Example: If 30 students out of 100 passed an exam, what percentage passed?

1. Divide: 30 / 100 = 0.3
2. Multiply: 0.3 × 100 = 30%
3. Answer: 30% of the students passed

Calculating Percentage Change

Percentage change measures how much a quantity has increased or decreased.

Example: If a company's revenue went from $500,000 to $600,000, what was the percentage change?

1. Subtract: 600,000 - 500,000 = 100,000
2. Divide: 100,000 / 500,000 = 0.2
3. Multiply: 0.2 × 100 = 20%
4. Answer: The revenue increased by 20%