How to Describe a Process Diagram in IELTS Writing Task 1

Some Academic Task 1 questions show stages instead of numbers. In a process diagram, the key features are the stages and the order they come in. This guide shows how to read the diagram, write the overview and link the stages. It is part of the Writing Task 1 guide, which covers the charts and the rules every Task 1 answer shares.

What a process task asks

You report the stages of the process in order. You do not need to know the topic beforehand.

The task can test whether you can describe the stages of a process or procedure, and explain how something works source: ielts.org.

Using the right language to describe the process matters more than knowing exactly how the process works source: IDP.

So the labels on the diagram give you the facts. Your job is the language that joins them.

Read the diagram before you write

Spend your first minute reading, not writing. A process has an order, and you need to see all of it before you describe any part.

A process diagram can show a cycle, such as the life cycle of a frog from egg to adult source: IDP. Questions to ask for the overview include whether it is cyclic or linear, how many stages it has, and what machinery is used source: IDP.

Here is an invented process. The rest of this guide uses it.

Invented data, drawn by Compass IELTS to show how a process diagram is described. Not an IELTS task.

Show the data

Invented process: How a small workshop turns rainwater into drinking water, stage by stage

Stage	Step	What happens
1	Rain collected	Rain runs off the workshop roof into gutters.
2	Stored in tank	The water is held in a covered tank.
3	Sand filter	It passes through layers of sand and gravel, which hold back dirt.
4	UV treatment	Ultraviolet light kills any bacteria left in the water.
5	Quality tested	A sample from each batch is tested.
6	Bottled	The water is bottled and labelled.

This process runs in a line. It has six stages, from rain on a roof to a labelled bottle. Stages 3, 4 and 5 all clean or check the water, so they make a natural group.

The overview

The overview tells the reader the size and shape of the process before any detail.

An overview summarises the main points, including the number of steps source: ielts.org. In the overview, summarise the important features of the process, and keep the specifics for the detail paragraphs source: IDP.

Here is one overview of the sample, written for this page.

Overall, there are six stages,^{note 1} from collecting rain on a roof to bottling the clean water.^{note 2} Three of the stages clean or check the water.^{note 3}

1. An overview "summarises the main points. That is, the main trends, changes, or number of steps" source: ielts.org. The count tells the reader how long the process is before any stage is described.
2. A key feature might be "the steps in a process" source: ielts.org. The first and last stages show where the process starts and ends, in one clause.
3. At band 7, "the data are appropriately categorised" source: ielts.org. The middle stages are grouped by what they do. That is categorising, on a diagram with no numbers.

Describe the stages in order

Take the stages in the order the diagram gives, and link each one to the next.

Learners should practise sequencing words, such as firstly and next source: ielts.org.

At band 6, cohesion "may be faulty or mechanical due to misuse, overuse or omission". At band 8, "information and ideas are logically sequenced" source: ielts.org.

Overuse is the risk in a process answer. Six stages tempt you to start six sentences with "then". Use a range instead: first, next, after that, at the next stage, finally. Words such as "once" and "after" can also join two stages in one sentence.

Group the stages into paragraphs. In the sample, stages 1 and 2 collect and store the water, and stages 3 to 6 clean, test and bottle it. That gives two body paragraphs of a sensible size.

This grouping is not the same as the overview's, and that is fine. The overview groups stages by their job. The paragraphs split the six stages into two parts of a similar length.

A process report has the same layout as other Task 1 reports: an introduction, an overview, and detail paragraphs source: IDP.

When the passive helps

The passive is useful when the diagram shows what happens to a thing, not who does it. Use it where it fits the meaning, not in every sentence.

IDP's advice differs from page to page. On one page, the passive voice is the rule for processes, maps and developments source: IDP. On another, the passive voice is often necessary when describing a process source: IDP.

Neither line is a marking rule. Our advice sits closer to the second one: most process stages suit the passive, but not all of them.

In the sample, the water is the subject of most stages. It is collected, stored, filtered, treated, tested and bottled. No person is shown, so "the water is filtered" is more accurate than "workers filter the water".

Some stages have a subject that acts by itself. "Rain runs off the roof" and "the sand holds back dirt" are active, and they are correct.

For bands 7 and above, you also need complex structures in your writing. They include passive forms source: ielts.org.

Diagrams give you labels to support your main points. Still, write your own words, including verbs, in the right tense and voice source: IDP.

A process like this one has no time period. With no time period, use the present tense source: IDP.

Here is part of a body paragraph for stages 3 and 4, written for this page.

Next,^{note 1} the water is passed through layers of sand and gravel,^{note 2} which hold back any dirt. Once it has been filtered,^{note 3} it is treated with ultraviolet light^{note 4} to kill any bacteria.

1. Learners should practise sequencing words, such as firstly and next source: ielts.org. "Next" moves the reader from the stages before to stage 3.
2. Complex structures include passive forms source: ielts.org. The water is the subject, and the diagram shows no person doing the work.
3. At band 7, "a range of cohesive devices including reference and substitution is used flexibly" source: ielts.org. "Once it has been filtered" joins stage 3 to stage 4. The word "it" refers back to the water instead of repeating it.
4. Write your own words, including verbs, rather than only the labels source: IDP. The label says "UV treatment". The sentence turns it into a verb and says what the light is for.

Stages 5 and 6 would finish this paragraph. We stop at stage 4, because this guide shows parts of an answer and never a whole one.

What changes from band 6 to band 7

The step from band 6 to band 7 on a process is from listing stages to showing the shape of the whole.

The band 5 line names "a tendency to focus on details (without referring to the bigger picture)" source: ielts.org. The band 6 and band 7 lines are quoted in full in the Writing Task 1 guide.

On a process, details without the bigger picture means six stages with no overview and no grouping. Check two things. Does your overview give the number of stages, the start and the end? Do your paragraphs group stages that belong together?

The overview and the grouping count under Task Achievement. The linking words count under Coherence and Cohesion. How IELTS Writing is marked covers both, and the band score calculator turns section bands into an overall score.

If your task shows a place at two times, read how to describe a map. General Training candidates write a letter instead: see the General Training letter. How to improve your IELTS Writing score shows what each band step asks for.

The task wording comes from ielts.org's Academic Writing format page. The points on overviews, key features and complex structures come from its Writing test resources page, and the point on sequencing words from its article on preparing learners for Task 1. The band wording comes from the Writing band descriptors (updated May 2023). The points marked IDP come from IDP Canada's articles on process diagrams and phrases for diagrams and maps, and IDP's article on common Task 1 types. The band descriptors PDF was last opened on 26 September 2026. The other pages were last checked on 3 October 2026. The process and examples were made up for this page and are not from any test.

Frequently asked questions

Should every sentence be in the passive?

Not in our view. Use the passive where nothing in the diagram shows who does the action, and the active where the subject acts by itself.

On one IDP page, the passive voice is the rule for processes source: IDP. On another, it is often necessary for a process source: IDP. Passive forms are one of the complex structures that count for bands 7 and above source: ielts.org.

Can I leave out a stage?

No. Cover every numbered stage, because each one is part of the main chain.

Some minor points or details may be left out source: ielts.org.

On a process diagram, those are the small details inside a stage.

Which tense should I use?

The present, if the diagram shows no time period source: IDP.