Figures or Words? How to Write Numbers in IELTS Task 1

Candidates ask whether to write 30% or thirty percent, and they expect a rule. There is no such rule. IELTS does not mark number formatting, so both forms are acceptable.

What is marked is whether the number says what the chart says. A separate guide covers which numbers to select from the data. This one covers how to write them once you have chosen, because most lost marks here are not about digits at all. They are about the small words around the number: by, to, percent, percentage point, of. Those words sit inside two criteria, Lexical Resource, which is the range and precision of your vocabulary, and Grammatical Range and Accuracy, which is your control of sentence structure.

Digits or words: pick one habit and stop thinking about it

Both are correct. Digits are shorter, faster to write, and harder to misread, which matters in a twenty minute task. The practical habit is this.

The one thing to avoid is mixing the two forms for the same quantity in the same answer. Writing 35% in one sentence and thirty five percent in the next is not an error, but it reads as carelessness, and carelessness is what the reader is trained to notice.

Do not spell out long figures. Four point two million costs you eight words of your word budget and gives the reader nothing that 4.2 million did not.

The error that actually costs marks: percent against percentage point

This is the most common number mistake in Task 1, and it is a meaning error rather than a style one.

If a figure moves from 20% to 30%, two different true statements are available.

• It rose by 10 percentage points. This is the simple subtraction.
• It rose by 50 percent. This is the change relative to where it started, because 10 is half of 20.

Saying "it rose by 10 percent" when the chart shows 20% to 30% is wrong. The reader can see the chart, so the sentence reports data that is not there. That is a Task Achievement problem, not a vocabulary one, and it is the reason this pair of words is worth learning properly.

If you are unsure, use the safe form: rose from 20% to 30%. It states both endpoints, it cannot be wrong, and it needs no arithmetic under exam pressure.

By and to are not interchangeable

These two prepositions carry the whole meaning of a trend sentence.

• Sales rose to 40% means 40% is the final figure.
• Sales rose by 40% means the increase itself was 40%, so the final figure is something else.

A reader who meets by where you meant to gets a different number from the one on the page. Two fixes make this reliable. First, use from X to Y whenever you can, because it names both ends and removes the ambiguity. Second, when you use by, put the word of nowhere near it; an increase of 40% and increased by 40% are both correct, while increased by an increase of is the kind of sentence that appears when a candidate is combining two memorised patterns.

Approximation language that stays accurate

You will not always want the exact figure, and you should not always give it. Rounding is normal in an overview. The risk is a word that rounds in the wrong direction.

Just under, just over, nearly, approximately, roughly and around are enough for any chart. They show range in Lexical Resource and they stay true to the data. What they must not do is contradict the direction: 48% is not over half, and a reader with the chart in front of them sees that immediately.

The grammar of a number phrase

Three patterns cover almost every sentence you need, and each one is a different structure, which is what Grammatical Range measures.

1. Verb pattern. The proportion of households with internet access rose from 20% to 55% between 2000 and 2010.
2. Noun pattern. There was a sharp rise in internet access, from 20% in 2000 to 55% in 2010.
3. Comparison pattern. At 55%, internet access was almost three times the 2000 figure.

Using all three in one answer is how a Task 1 response stops sounding like a list. Using only the first is the most common reason a technically correct answer stays at band 6.

Two accuracy points inside these patterns. The number of takes a countable plural noun, so the number of visitors. The amount of takes an uncountable noun, so the amount of electricity. And a percentage used as a subject is singular: 35% of the population was born abroad, when the noun after of is singular.

Before and after

A real paragraph with number errors, then the same content repaired.

Before: In 2000 the internet access was 20 percent and it increased by 55 percent in 2010 which is more than double. The amount of households was also rise in the same period by 10 percent approximately about a third.

Four separate problems: increased by 55 percent reports a change that is actually an endpoint, the amount of households takes the wrong quantifier, was also rise is a verb form error, and the final clause gives two different approximations for one figure.

After: Household internet access rose from 20% in 2000 to 55% in 2010, almost tripling over the decade. The number of connected households increased by roughly a third in the same period.

The second version is shorter, and every number in it can be checked against the chart. That is the only test that matters.

Do this today

Take any Task 1 answer you have already written. Circle every number in it. For each one, write in the margin whether it is an endpoint or a change, then check that the preposition in front of it is to for an endpoint and by for a change. Then check every approximation word against the real figure and ask whether it rounds in the right direction.

Most candidates find two or three errors in a single paragraph, and they are all cheap to fix. You can paste the corrected answer into Bandly for an estimated band on each of the four criteria, with the sentences that carry the weakest grammar marked, so you can see whether the repairs moved anything.