Question 1

How do you convert a decimal to a percentage?

Accepted Answer

Multiply the decimal by 100 and add a "%" sign (or equivalently, move the decimal point two places to the right). 0.45 × 100 = 45%; 0.075 × 100 = 7.5%; 1.25 × 100 = 125%. This works because "percent" (from Latin per centum) means "per hundred" — so percent is just the decimal multiplied by the 100-base denominator. Values above 1.0 become percentages above 100% (meaning more than the whole).

Question 2

How do you convert a percentage back to a decimal?

Accepted Answer

Divide the percentage by 100 (or move the decimal point two places to the left). 45% ÷ 100 = 0.45; 7.5% = 0.075; 150% = 1.5; 0.5% = 0.005. Common errors: 5% is 0.05, not 0.5 (a factor-of-10 mistake that causes major calculation errors). When multiplying by a percentage in a formula, always convert to decimal first: "increase by 15%" means multiply by 1.15; "decrease by 15%" means multiply by 0.85.

Question 3

How do percentages work in spreadsheets and programming?

Accepted Answer

In Excel and Google Sheets, cells formatted as "Percentage" display the underlying decimal multiplied by 100. A cell containing 0.45 shows as 45%. When writing formulas, use the decimal form (=A1*0.15, not =A1*15%). In Python/JavaScript, the % operator is the modulus operator (remainder), not percentage — always divide by 100 manually: tax = price * 0.15. This distinction catches many beginners who write "price * 15%" and get a syntax error or wrong result.

Question 4

What is percentage increase and decrease, and how is it calculated?

Accepted Answer

Percentage change = ((New Value − Old Value) ÷ Old Value) × 100%. Increase: price goes from $50 to $65 → ((65−50)÷50) × 100 = 30% increase. Decrease: from $80 to $60 → ((60−80)÷80) × 100 = −25% (a 25% decrease). To apply a percentage increase: New value = Old × (1 + rate). To apply a decrease: New = Old × (1 − rate). A 50% decrease followed by a 50% increase does NOT return to the original: $100 → $50 → $75 (not $100).

Question 5

What is the difference between percentage points and percent change?

Accepted Answer

This is one of the most misused distinctions in statistics and journalism. Percentage points are the arithmetic difference between two percentages. Percent change is the relative change. Example: interest rate rises from 2% to 5%. The increase is 3 percentage points (5 − 2 = 3 pp), but a 150% increase relative to the original (3 ÷ 2 × 100 = 150%). "Interest rates doubled" would be incorrect (that would mean rising to 4%); "rates rose 3 percentage points" and "rates rose 150%" are both accurate but describe different things.

Decimal to Percent Converter

Everyday Uses

Reading reports

Statistics homework

Interest rate clarity

Spreadsheet prep

Sale prices

Tips and service charges

Frequently Asked Questions

How do you convert a decimal to a percentage?

How do you convert a percentage back to a decimal?

How do percentages work in spreadsheets and programming?

What is percentage increase and decrease, and how is it calculated?

What is the difference between percentage points and percent change?

Related Calculators

Everyday Uses

Reading reports

Statistics homework

Interest rate clarity

Spreadsheet prep

Sale prices

Tips and service charges

Frequently Asked Questions

How do you convert a decimal to a percentage?

How do you convert a percentage back to a decimal?

How do percentages work in spreadsheets and programming?

What is percentage increase and decrease, and how is it calculated?

What is the difference between percentage points and percent change?