Place Value and Rounding
7 min read · Updated September 26, 2026 · by the SolveCalcPro editorial team
The value of a digit depends on where it sits. In 4,829.317 the 8 means eight hundreds but the 3 means three tenths. Understanding place value is the base of all arithmetic, and it is what makes rounding and estimating make sense.
Place value chart
| Digit | 4 | 8 | 2 | 9 | . | 3 | 1 | 7 |
|---|---|---|---|---|---|---|---|---|
| Place | thousands | hundreds | tens | ones | tenths | hundredths | thousandths |
Each place is ten times the one to its right.
Expanded form
4,829.317 = 4,000 + 800 + 20 + 9 + 0.3 + 0.01 + 0.007. Writing numbers this way shows what each digit is worth.
Comparing numbers
Line up the decimal points and compare digits from the left. 0.45 and 0.5: compare tenths, 4 versus 5, so 0.5 is larger even though 45 looks bigger than 5. Adding zeros helps: 0.50 versus 0.45.
Rounding
Find the place you are rounding to, then look at the digit to its right. If it is 5 or more, round up; if 4 or less, leave it. 4,829.317 to the nearest hundred is 4,800; to the nearest ten is 4,830; to the nearest tenth is 4,829.3. Use the rounding calculator to check.
Big numbers
Groups of three digits get names: thousand, million (1,000,000), billion (1,000,000,000) and trillion. Very large numbers are easier in scientific notation.
Practice questions
Test yourself, then tap to check. Answers are calculated by the tools linked below.
- Round 7.8449 to 2 decimal places.
Show answer
Rounded to 2 decimal places: 7.84
- Write 45,000,000 in scientific notation.
Show answer
Scientific notation: 4.5 × 10^7
- How many kilometres is a 26.2-mile marathon?
Show answer
26.2 mi in km: 42.1648128
Frequently asked questions
What is place value?
The value a digit has because of its position in the number.
How do I round to the nearest thousand?
Look at the hundreds digit. 5 or more rounds up. 6,478 becomes 6,000 and 6,578 becomes 7,000.
What is 0.4 compared with 0.04?
0.4 is ten times larger.
Why does rounding matter?
It gives simpler numbers for estimating and reporting results at an appropriate precision.
Try it yourself
Rounding CalculatorRound to decimal places, significant figures or the nearest 10, 100 or 1,000.
Scientific Notation ConverterConvert numbers to scientific, engineering and standard notation.
Unit ConverterConvert length, mass, temperature, volume, area and speed between metric and imperial units.Keep learning
Scientific Notation7 min readConverting Fractions, Decimals and Percents8 min readHow to Calculate Percentages7 min readWritten and reviewed by the SolveCalcPro editorial team. Spot a mistake? Tell us. See our editorial policy.