Adding Decimals: Column Method (Year 5–6)

D7Adding Decimals

Line up the points. Add column by column.

Adding decimals works like column addition — as long as the decimal points line up.

3.45 + 2.3 = ?

 3.45
+2.30
 5.75

Points lined up · zero padded on · add right to left → 5.75

Learn the 3-Step Method

1Line up the decimal points.

Write one number above the other with the points in a straight column.

3.45
2.3

2Pad with zeros.

Fill empty places: 2.3 → 2.30. Now every column is full.

3.45
2.30

3Add column by column.

Add from the right, carrying as usual. The point drops straight down.

5.75

💡 Key IdeaThe decimal point in the answer sits directly below the points above — nothing moves.

Worked Example

Work out 4.68 + 1.75.

Set up

 4.68
+1.75

→

Add hundredths

8 + 5 = 13 → write 3, carry 1

→

Add tenths, then ones

6 + 7 + 1 = 14 → write 4, carry 1
4 + 1 + 1 = 6

→

✓ Answer

6.43

Watch Out! Common Mistakes

Lining up the ends instead of the points.

3.45
+ 2.3

Wrong! Right-aligning makes the 3 add to hundredths. Line up the decimal points.

Forgetting the point in the answer.

3.45 + 2.30 = 575 ✕

Wrong! Drop the point straight down: the answer is 5.75.

Not carrying.

4.68 + 1.75 = 5.33 ✕

Wrong! 8 + 5 = 13: write 3, carry 1 into the tenths. Correct answer: 6.43.

⬇ Cheat Sheet

ADDING DECIMALS

Line up the decimal points vertically.
Pad empty places with zeros.
Add right to left, carrying as usual.
Drop the decimal point straight down into the answer.

Examples: 3.45 + 2.3 = 5.75 · 4.68 + 1.75 = 6.43

📖 Continue Your Journey

✓ D1 What Are Decimals?✓ D2 Place Value in Decimals ✓ D3 Decimals on a Number Line ✓ D4 Comparing Decimals ✓ D5 Ordering Decimals ✓ D6 Rounding Decimals D7 Adding Decimals D8 Subtracting Decimals D9 Multiplying by 10, 100 and 1000 D10 Dividing by 10, 100 and 1000 D11 Multiplying Decimals by Whole Numbers D12 Dividing Decimals by Whole Numbers D13 Fractions to Decimals D14 Decimal Problem Solving

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Next Lesson: D8 Subtracting DecimalsLine up the points. Subtract column by column.

📄 Free printable: Download the Adding Decimals cheat sheet (PDF) — keep it by your child's desk.

Quick summary

Line up the decimal points before you add anything.
Pad shorter numbers with zeros so every column is full.
Add right to left with normal carrying.
The decimal point drops straight down into the answer: 3.45 + 2.3 = 5.75.

Frequently asked questions

How do you add decimals step by step?

Write the numbers in columns with the decimal points lined up, pad with zeros so they're the same length, then add column by column from the right, carrying as usual.

Why must decimal points line up?

So that tenths add to tenths and hundredths to hundredths. If you right-align 3.45 and 2.3 instead, you'd wrongly add 3 tenths to 5 hundredths.

What is 3.45 + 2.3?

5.75. Pad 2.3 to 2.30, then add: 3.45 + 2.30 = 5.75.

D8 Subtracting Decimals