How do you add decimals with different numbers of decimal places?

Line up the decimal points and fill the empty places with zeros so both numbers have the same number of decimal places. For example, 97.9 + 3.137 becomes 97.900 + 3.137 = 101.037.

Why do you line up the decimal points?

So that each digit is added to a digit with the same place value: ones to ones, tenths to tenths, hundredths to hundredths. Lining up the last digits mixes up the places.

Does adding a zero to the end of a decimal change its value?

No. 2.5, 2.50 and 2.500 are the same number. A zero at the end of the decimal part only says there are no hundredths or thousandths, and it makes lining up easier.

How do you subtract a decimal from a whole number?

Write the whole number with a decimal point and zeros, then subtract as usual, exchanging across the zeros. For example, 20 − 6.14 = 20.00 − 6.14 = 13.86.

What grade learns adding and subtracting decimals?

In the US Common Core, grade 5 covers decimals to hundredths (5.NBT.B.7), and grade 6 expects fluency with multi-digit decimals (6.NS.B.3). In England it is mainly Year 5, building on money and measure problems in Year 4.

Is there a free adding and subtracting decimals worksheet with answers?

Yes. Use the Print a worksheet button on this page. Each worksheet is freshly made, and the answer key can show answers only or answers with worked steps.

Grades 5 and 6 (Years 5 and 6 in England)

Adding and subtracting decimals

Adding decimals and subtracting decimals both come down to one habit: line up the decimal points. Here is the method step by step, with a fully worked example and plenty more at different levels. Try the free practice set below, then print a fresh worksheet with an answer key.

The method, step by step

Write the numbers in a column so the decimal points sit directly under each other.
Fill any empty decimal places with zeros, so both numbers have the same number of digits after the point.
Add or subtract from the right, one column at a time, just as you would with whole numbers.
Carry or exchange across the decimal point exactly as you would between any other two columns.
Put the decimal point in the answer directly below the decimal points in the question.
Check with an estimate: round each number to the nearest whole number and see if your answer is close.

CCSS 5.NBT.B.7CCSS 6.NS.B.3England: Y5 Fractions (including decimals)England: Y6 Fractions (including decimals)England: KS3 Number

Worked example

12.6 + 4.75 = ?

Write 12.6 above 4.75 with the decimal points in one column.
12.6 has one decimal place and 4.75 has two, so write 12.6 as 12.60. The value does not change.
Hundredths: 0 + 5 = 5.
Tenths: 6 + 7 = 13. Write 3 and carry 1 into the ones column.
Ones: 2 + 4 + 1 = 7. Tens: 1.
Estimate to check: 13 + 5 = 18, which is close.
12.6 + 4.75 = 17.35

Practice now

Question 1 of 100 correct

3.63 − 2 = ?

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Why lining up the decimal points works

Every column in a number has a value: tens, ones, tenths, hundredths and so on. You can only combine digits of the same value, so tenths must be added to tenths and hundredths to hundredths. Lining up the decimal points is simply the quickest way to make sure every digit sits in the right column.

Money makes it easy to picture. $3.40 + $1.25 is 3 dollars and 4 dimes plus 1 dollar, 2 dimes and 5 cents. Dollars go with dollars, dimes with dimes and cents with cents, so the total is 4 dollars, 6 dimes and 5 cents, or $4.65. Writing 3.4 as 3.40 does not change the amount. It just shows that there are no extra cents.

On a hundred square, where the whole square is 1, each column is one tenth and each small square is one hundredth. Adding 0.8 and 0.7 fills 15 columns: one whole square and 5 more columns. That is why 0.8 + 0.7 = 1.5, and why a carry can cross the decimal point into the ones.

Adding and subtracting decimals: more examples

These examples get a little harder each time. The method never changes: line up the points, fill gaps with zeros, then work from the right.

Same number of places: 2.5 + 3.4 = 5.9.
A carry across the point: 0.8 + 0.7 = 1.5. Ten tenths make one whole, so the 1 moves into the ones column.
Different numbers of places: 97.9 + 3.137. Write 97.9 as 97.900, then 97.900 + 3.137 = 101.037.
Subtracting with an exchange: 8.42 − 5.7 = 8.42 − 5.70 = 2.72. In the tenths column, 4 − 7 needs an exchange, so one of the 8 ones becomes 10 tenths.
Subtracting from a whole number: 20 − 6.14. Write 20 as 20.00, exchange across the zeros and get 13.86.
A two-step money problem: items cost $2.35 and $1.80, and you pay with $5. The total is 2.35 + 1.80 = 4.15, so the change is 5.00 − 4.15 = $0.85.

Subtracting decimals across zeros

The question children find hardest is a whole number minus a decimal, such as 5 − 2.36. Write 5 as 5.00. There are no tenths or hundredths to take from, so exchange one of the 5 ones for 10 tenths, then one of those tenths for 10 hundredths. That leaves 4 ones, 9 tenths and 10 hundredths. Now subtract column by column: 10 − 6 = 4 hundredths, 9 − 3 = 6 tenths and 4 − 2 = 2 ones, so 5 − 2.36 = 2.64.

Counting up is a good mental check, and it is how many people work out change. From 2.36, add 0.04 to reach 2.40, add 0.60 to reach 3, then add 2 to reach 5. Altogether that is 0.04 + 0.60 + 2 = 2.64.

Estimating to catch mistakes

Before you calculate, round each number to the nearest whole number. 19.8 + 6.45 is about 20 + 6 = 26, and the exact answer is 26.25. If you got 8.43, the digits were lined up on the right instead of at the decimal point, which turns 19.8 into 1.98 by mistake.

A misplaced decimal point is a very common slip with decimals, and an estimate catches it in seconds. Get into the habit of saying the estimate out loud before writing the exact answer.

How it is taught in school

In the US, Common Core expects grade 5 students to add and subtract decimals to hundredths using models, drawings and place value, and to connect those strategies to a written method (5.NBT.B.7). By grade 6, students add and subtract multi-digit decimals fluently with the standard algorithm (6.NS.B.3).

In England, Year 4 pupils solve simple money and measure problems with decimals to two decimal places. The Year 5 guidance has pupils adding and subtracting decimals, including a mix of whole numbers and decimals, decimals with different numbers of decimal places, and complements of 1 such as 0.83 + 0.17 = 1.

How parents can help

Use real prices. Add two items from a receipt or a menu, then work out the change from a round amount.
Say decimals by place: 3.45 is 'three and forty-five hundredths' or 'three point four five', not 'three point forty-five', which hides what each digit is worth.
Ask for an estimate first, then let your child check the exact answer against it.
Measure things. Add two heights in meters, or find the difference between two race times in seconds.
Keep sessions short. Print a fresh worksheet, let your child mark it with the answer key, and read the worked steps together for any they missed.

Common mistakes

Lining up the last digits instead of the decimal points. 19.8 + 6.45 is not 8.43; with the points lined up it is 19.80 + 6.45 = 26.25.
Writing 0.8 + 0.7 = 0.15. Ten tenths make a whole, so the answer is 1.5.
Taking the smaller digit from the bigger one in each column. In 8.42 − 5.7 the tenths column is 4 − 7, so exchange a one for 10 tenths instead of working out 7 − 4.
Bringing the decimal part straight down when subtracting from a whole number. 5 − 2.36 is not 3.36. Write 5 as 5.00 and exchange across the zeros to get 2.64.
Leaving out the decimal point in the answer, or putting it somewhere else. Bring it straight down from the question.

Questions people ask

How do you add decimals with different numbers of decimal places?: Line up the decimal points and fill the empty places with zeros so both numbers have the same number of decimal places. For example, 97.9 + 3.137 becomes 97.900 + 3.137 = 101.037.
Why do you line up the decimal points?: So that each digit is added to a digit with the same place value: ones to ones, tenths to tenths, hundredths to hundredths. Lining up the last digits mixes up the places.
Does adding a zero to the end of a decimal change its value?: No. 2.5, 2.50 and 2.500 are the same number. A zero at the end of the decimal part only says there are no hundredths or thousandths, and it makes lining up easier.
How do you subtract a decimal from a whole number?: Write the whole number with a decimal point and zeros, then subtract as usual, exchanging across the zeros. For example, 20 − 6.14 = 20.00 − 6.14 = 13.86.
What grade learns adding and subtracting decimals?: In the US Common Core, grade 5 covers decimals to hundredths (5.NBT.B.7), and grade 6 expects fluency with multi-digit decimals (6.NS.B.3). In England it is mainly Year 5, building on money and measure problems in Year 4.
Is there a free adding and subtracting decimals worksheet with answers?: Yes. Use the Print a worksheet button on this page. Each worksheet is freshly made, and the answer key can show answers only or answers with worked steps.

Updated November 1, 2026.

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