Rounding Numbers

Rounding means replacing a number with a nearby, simpler number that is close in value. It is used every day for estimating, quick calculations, and reporting figures that do not need to be exact.

The Rounding Rule

Look at the digit immediately to the right of the rounding place.
If it is 0–4, round down (keep the rounding digit as it is).
If it is 5–9, round up (increase the rounding digit by 1).
Replace all digits to the right of the rounding place with zeros.

Rounding to the Nearest Ten

63 → ones digit is 3 (less than 5) → round down → 60

67 → ones digit is 7 (5 or more) → round up → 70

Rounding to Various Places

Number	Round to Nearest	Digit to Check	Result
4,372	Hundred	Tens digit = 7 (≥5)	4,400
4,372	Thousand	Hundreds digit = 3 (<5)	4,000
56,851	Ten	Ones digit = 1 (<5)	56,850
99,950	Hundred	Tens digit = 5 (≥5)	100,000

Using a Number Line

Find the number on a number line. It will sit between two multiples of the rounding unit. The closer multiple is the rounded value. If exactly halfway, round up.

35 rounded to nearest 10: halfway between 30 and 40 → round up → 40

Rounding Decimals

Number	Round to	Digit to Check	Result
3.74	Nearest whole	Tenths = 7 (≥5)	4
3.74	1 decimal place	Hundredths = 4 (<5)	3.7
2.485	2 decimal places	Thousandths = 5 (≥5)	2.49

Estimating with Rounding

389 + 212 ≈ 400 + 200 = 600 (quick estimate)

Key Points

Identify the rounding place, then look one digit to its right.
0–4: round down (the rounding digit stays); 5–9: round up (add 1).
Replace all digits to the right of the rounding place with zeros.
Rounding may cause a carry that changes several digits (e.g., 9,950 → 10,000).
Rounding helps estimate and simplify calculations.

Practice: Round the Number

Round the number below to the place shown. If you get it wrong (or leave it blank), we'll check the key digit together.

Round this number:

Summary

Rounding is a controlled simplification: you choose a place, check the next digit to the right, and adjust accordingly. It is the key to estimation, measurement, and data reporting. For decimals the process is identical, just applied to decimal place columns instead of whole-number columns.