Column Addition Explained: Carrying Made Simple
By the TimesTable.co team · Updated · 3 min read
Column addition is the first written method most children learn, and it's the foundation for column subtraction, long multiplication and adding decimals. The idea is simple, but carrying (now often called "exchanging" or "regrouping") is where mistakes creep in. Here's the method step by step.
How do you set out column addition?
Write the numbers one above the other, lined up on the right so that ones are under ones, tens under tens and hundreds under hundreds. Draw a line underneath and leave room for the answer. Place-value headings (H, T, O) help at first. Our column addition practice shows these headings above each column.
How do you add without carrying?
23 + 45
- Ones: 3 + 5 = 8.
- Tens: 2 + 4 = 6.
- Answer: 68.
How does carrying work?
47 + 35
- Ones: 7 + 5 = 12. That's 1 ten and 2 ones. Write 2 in the ones column and carry a small 1 under the tens column.
- Tens: 4 + 3 + the carried 1 = 8.
- Answer: 82.
The key idea: ten ones are exchanged for one ten. Making it concrete with coins (ten 1p coins swapped for a 10p) or base-ten blocks helps enormously.
What about bigger numbers?
2,587 + 1,648
- Ones: 7 + 8 = 15 → write 5, carry 1.
- Tens: 8 + 4 + 1 = 13 → write 3, carry 1.
- Hundreds: 5 + 6 + 1 = 12 → write 2, carry 1.
- Thousands: 2 + 1 + 1 = 4.
- Answer: 4,235.
How do you add decimals in columns?
Line up the decimal points, not the right-hand edges. If one number has fewer decimal places, add a zero as a placeholder: 45.67 + 23.8 becomes 45.67 + 23.80. Add as normal and bring the point straight down: 69.47. Our column addition has a Decimals level for exactly this.
What are the most common mistakes?
- Numbers lined up on the left instead of the right (hundreds under tens).
- Forgetting to add the carried 1.
- Writing 12 in a single column instead of carrying.
- Starting from the left.
How can you check an answer?
Estimate first: 47 + 35 is about 50 + 35 = 85, so 82 is sensible and 712 isn't. Or check with the inverse: 82 − 35 should give 47, which is practice for column subtraction.
How can you practise at home?
Start with 2-digit numbers without carrying, then add carrying, then move up a digit at a time. The column addition tool goes from single digits to 4-digit numbers and decimals, prompting each column in turn and celebrating each finished sum. For paper practice, the worksheet generator makes addition sheets with answer keys. Seeing jumps on a number line helps younger children with mental addition too.
What comes after column addition?
The same column layout is used in column subtraction and in adding the rows of long multiplication. Decimal sums also link to fractions, decimals and percentages, which the decimals explorer shows visually.
Frequently asked questions
What is column addition?
A written method where numbers are lined up by place value (ones under ones, tens under tens) and added one column at a time, starting from the ones.
What does carrying mean in addition?
When a column adds up to 10 or more, the ten is carried into the next column as a small 1. For example, 7 + 5 = 12 in the ones column: write 2 and carry 1 ten.
Why do you start from the right in column addition?
Starting with the ones means any carried ten can be added into the tens column before you work it out. Starting from the left would mean going back to change answers.
What year is column addition taught?
In England, children start the formal written method in Year 3 and use it with larger numbers in Year 4, and with decimals in Year 5 and 6.
Is carrying the same as regrouping?
Yes. Many schools now say "exchanging" or "regrouping" instead of carrying, because ten ones are exchanged for one ten. The method is the same.
How do you add decimals in columns?
Line up the decimal points first, fill any gaps with zeros (23.8 becomes 23.80), then add as usual and bring the decimal point straight down into the answer.