Once you get the hang of rounding numbers, you’ll begin to use it every day, from balancing your checkbook to estimating your grocery bill. In this post, we’ll show you how to round to the nearest tenth (or any decimal place, for that matter).
What Does Rounding Numbers Mean?
Rounding numbers makes a number simpler to work with but still close to the original value. Because you are changing the place value of some of the digits though, the rounded number is only a guess — not the exact correct answer.
The same goes for rounding decimals or numbers that come after the decimal point.
Let's review what each place value digit represents:
The ones digit represents the whole numbers you normally use to count something, like apples (4.0 apples = four apples).
The tenths digit represents one-tenth of an item, like if you were to split a pizza into 10 equal pieces to share (0.2 of a pizza = two slices of a 10-slice pizza).
The hundredths digit represents one-hundredth of something. In the United States, our currency is set up such that a penny, or one cent, is worth one one-hundredth of a dollar (1 penny = $0.01).
Rounding To the Nearest Tenth
Whenever you want to round a number to a particular digit, look only at the digit immediately to its right. For example, if you want to round to the nearest tenth, look to the right of the tenths place: This would be the hundredths place digit. Then, if it is 5 or higher, you get to add one to the tenths digit. If it is 4 or lower, the tenths digit remains the same.
For example, 3.58 can be rounded to 3.6 because the hundredths place digit, 8 is greater than or equal to 5.
3.32 would be rounded to 3.3, because the hundredths place digit, 2, is less than 5.
Rounding To the Nearest Hundredth
The same goes for rounding to the nearest hundredth. Take the number 14.225 for example.
The hundredths place digit is 2, and we want to determine whether to keep it the same or round up.
The thousandths place digit is 5. Since it is 5 or higher, 14.225 gets rounded to 14.23.
Rounding Across the Decimal
Does the same apply across the decimal place? You bet. If you want to round to the nearest whole number — another way of saying to the unit or ones digit — you will look to the first digit to the right of the decimal point. That’s right, that’s the tenth digit.
4.0 rounds to 4 because the 0 is less than 5.
4.3 also rounds to 4 because 3 is less than 5.
4.6 rounds to 5 because 6 is greater than or equal to 5.
One Rule to Remember
Whether you're on the left side or the right side of the decimal point or using slightly different definitions for how to round, the only digit you really have to pay attention to is the digit immediately to the right of the digit place you want to round to. If you are rounding to the tens digit, look at the ones digit. If you are rounding to the nearest thousandth, look at the ten-thousandths digit.
And that's it! Go forward and round with confidence, no matter where on the number line you are.