The basic method: multiply by 100 and add the % sign
To change a decimal to a percentage, multiply the decimal by 100 and then add the percent symbol (%). That is the entire process. A decimal like 0.65 becomes 65% because 0.65 × 100 = 65.
The reason this works is that a percentage is always a number out of 100. When you multiply a decimal by 100, you are moving the decimal point two places to the right. So 0.65 becomes 65, and 0.05 becomes 5, and 0.5 becomes 50.
You can use a calculator for this, or do it by hand. Either way, the step is the same: multiply by 100, then write the % symbol after your answer.
Key Takeaways
- Multiply the decimal by 100 and add a percent sign — that is the complete conversion.
- Moving the decimal point two places to the right gives you the same result as multiplying by 100.
- A decimal like 0.75 becomes 75%, and 0.08 becomes 8%.
- Decimals smaller than 0.01 become percentages smaller than 1%, such as 0.005 becoming 0.5%.
Moving the decimal point instead of multiplying
If you prefer not to multiply, you can move the decimal point two places to the right. This gives the same answer because moving the decimal point two places is what multiplying by 100 does.
Start with 0.42. Move the decimal point two places right: 0.42 becomes 42. Then add the % sign: 42%. The decimal point in 42 is at the end (42.0), but you do not need to write it.
For a decimal like 0.5, moving the decimal two places right gives you 50. So 0.5 = 50%. For 0.125, you get 12.5%, because the decimal point moves from between the 1 and 2 to between the 2 and 5.
What to do when the decimal has more than two places
Decimals with three or more places work the same way. Multiply by 100 (or move the decimal two places right), and the result is your percentage.
Take 0.335. Multiply by 100: 0.335 × 100 = 33.5. Add the % sign: 33.5%. Or move the decimal: 0.335 becomes 33.5, then add %.
For 0.0625, multiply by 100 to get 6.25, so the percentage is 6.25%. For 0.00875, you get 0.875%. The decimal point moves the same way no matter how many digits are after it.
Decimals larger than 1
A decimal larger than 1 becomes a percentage larger than 100%. This is correct and happens when something is more than a whole.
If a price increases from $10 to $25, the decimal form of that increase is 2.5 (because 25 ÷ 10 = 2.5). Multiply by 100: 2.5 × 100 = 250. So the price is now 250% of what it was, or it increased by 150%.
The method does not change. Multiply by 100, add the % sign. A decimal of 1.5 becomes 150%, and 3.2 becomes 320%.
Very small decimals and percentages less than 1%
When a decimal is smaller than 0.01, the percentage will be smaller than 1%. The process is still the same: multiply by 100.
A decimal of 0.005 becomes 0.5% (because 0.005 × 100 = 0.5). A decimal of 0.0075 becomes 0.75%. A decimal of 0.001 becomes 0.1%. These are all valid percentages, even though they are less than 1%.
You may see these in contexts like interest rates, scientific measurements, or very small changes. The conversion method does not change.
Common examples you might see
| Decimal | Multiply by 100 | Percentage |
|---|---|---|
| 0.25 | 0.25 × 100 = 25 | 25% |
| 0.5 | 0.5 × 100 = 50 | 50% |
| 0.75 | 0.75 × 100 = 75 | 75% |
| 0.1 | 0.1 × 100 = 10 | 10% |
| 0.33 | 0.33 × 100 = 33 | 33% |
| 0.125 | 0.125 × 100 = 12.5 | 12.5% |
| 1.5 | 1.5 × 100 = 150 | 150% |
| 0.008 | 0.008 × 100 = 0.8 | 0.8% |
Frequently Asked Questions
Do I always add the % sign, or is it optional?
The % sign is not optional — it is what makes the number a percentage. Without it, 25 is just the number 25, not 25%. The symbol tells anyone reading it that the number represents a part of 100.
What if I move the decimal point the wrong direction?
If you move the decimal left instead of right, you will get a number that is 100 times too small. For example, 0.65 would become 0.0065 instead of 65. Check your answer: a percentage should usually be between 0% and 100% (unless the decimal was larger than 1 or smaller than 0.01).
Can I convert a percentage back to a decimal?
Yes — do the opposite. Divide the percentage by 100 (or move the decimal point two places to the left). So 65% becomes 0.65, and 8% becomes 0.08. This is useful when you need to use the percentage in a calculation.
What about repeating decimals like 0.333...?
Multiply by 100 the same way: 0.333... × 100 = 33.333...%, which is often written as 33.3% or 33⅓%. Round to as many decimal places as you need for your purpose.