Decimal Point — Definition, Formula & Examples
A decimal point is the dot (.) placed in a number to separate the whole-number part on the left from the fractional part on the right. For example, in 3.75, the decimal point sits between the 3 and the 75.
The decimal point is a symbol (typically a period in the US) that denotes the boundary between the units (ones) place and the tenths place in a base-ten numeral, indicating where the integer portion ends and the fractional portion begins.
How It Works
Every digit to the left of the decimal point represents whole numbers: ones, tens, hundreds, and so on. Every digit to the right represents parts of a whole: tenths, hundredths, thousandths, and so on. Moving one place to the right of the decimal point divides the value by 10. So in 4.62, the 6 is worth six tenths and the 2 is worth two hundredths. If a number has no decimal point written, you can think of it as sitting invisibly at the far right — the number 8 is the same as 8.0.
Worked Example
Problem: What does each digit in the number 5.39 represent?
Identify the whole-number part: The digit to the left of the decimal point is 5. It sits in the ones place, so it represents 5 ones.
Identify the tenths digit: The first digit to the right of the decimal point is 3. It sits in the tenths place.
Identify the hundredths digit: The second digit to the right of the decimal point is 9. It sits in the hundredths place.
Answer: 5.39 means 5 ones + 3 tenths + 9 hundredths, or .
Why It Matters
You rely on the decimal point every time you read a price tag, measure a distance, or calculate a test score. Placing it in the wrong spot changes a value by a factor of 10 or more — the difference between $1.50 and $150.
Common Mistakes
Mistake: Shifting the decimal point one place when multiplying or dividing by 10, but moving it in the wrong direction.
Correction: Multiplying by 10 moves the decimal point one place to the right (making the number bigger). Dividing by 10 moves it one place to the left (making the number smaller).