What is a Decimal?
Numbered or ordered in groups of 10. A number written using base 10. Relating to tens or tenths.
A decimal is a way of writing numbers that can represent parts of a whole—or whole numbers—using a decimal point. It uses a decimal point to separate the whole number part from the fractional part.
Here’s what a decimal looks like:
- 0.5 means half (or 5 tenths)
- 2.75 means 2 whole units and 75 hundredths
- 4.0 means exactly 4 with no fractional part
Decimals are part of the base-ten system, just like whole numbers. Each place to the right of the decimal point is 10 times smaller than the one before it:
- 0.1 is one tenth
- 0.01 is one hundredth
- 0.001 is one thousandth
So, decimals help us describe numbers that fall between whole numbers—just as a fraction, right?
In fact, decimals and fractions are two different ways of showing parts of a whole, and learning decimals builds on what many students already know about fractions.
We use decimals every day:
- When dealing with money: $3.75 means 3 dollars and 75 cents
- Measuring distance: 1.5 miles means one and a half miles
- Tracking time: 0.25 hours (15 minutes)
When Do Students Learn About Decimals?
Most students are introduced to the idea of decimals in upper elementary school and continue building on this understanding through middle school.
Grades 3–4 – Introduction to Decimals
Students begin learning how decimals represent parts of a whole. They use number lines, grids, and money to understand tenths and hundredths.
Grade 5 – Working with Decimals
Students read, write, compare, and round decimals. They also begin adding, subtracting, multiplying, and dividing decimals using place value strategies.
Grades 6–7 – Advanced Decimal Operations
Students work with decimals in more complex problems, including percent calculations, measurement conversions, and multi-step word problems.
