How to use icons in worksheets and slides so they stay clear

A worksheet with a small picture of a telescope next to the astronomy questions looks friendly. A slide with a flask icon beside each chemistry step helps a learner find their place. Used well, small icons make study materials easier to scan. Used badly, they add clutter, vanish when printed small, or leave some readers behind. This guide is for teachers, tutors, parents and anyone who makes learning resources. It covers how to choose where an icon helps, how to test that it is legible at the size you use, and how to handle contrast, text alternatives and file formats.

Does the icon do a job?

Before you place an icon, ask what it is for. Useful jobs include:

Marking a category. A small planet beside every question about space, a leaf beside biology. The learner learns the code and finds the section quickly.
Marking a step or a type of task. A magnifying glass for "observe", a flask for "mix", a pencil for "write".
Anchoring a concept. A single clear drawing of a prism next to the word "refraction".
Making a page less intimidating for younger learners.

Be honest about the last one. Decoration has a cost. Mayer and Moreno (2003) reviewed ways to reduce the mental load of multimedia learning, and one of their suggestions, which they call weeding, is to remove interesting but extraneous material so that learners are not distracted from the core content. Their paper reviews research on learning from words and pictures, and it does not test any particular icon set, so treat it as a principle and not a promise. The practical lesson is plain: use icons where they help the learner do something, and cut the ones that are only there to fill space.

Be consistent

If a flask means "experiment" on page one, it should mean "experiment" on every page. Pick a small vocabulary of icons and use each for one job. A consistent style matters too: icons drawn with the same outline weight, the same level of detail and the same kind of border look like a family, and the learner stops noticing them as decoration and starts using them as signs. Mixing drawings from several sources makes a page look noisy and can hide the meaning.

Test at the real size

Icons are usually drawn large and shown small. A design that is clear at 1,024 pixels can turn into a smudge at 64. The test is easy: put the icon at the size you will actually use on the page or slide, on the real background, and look at it from the distance a learner will. Ask three questions. Can you tell what it is? Can you tell it apart from the others in the set? Does the outline hold up?

Do the arithmetic for outlines. Scaling a 1,024-pixel image down to 64 pixels reduces each dimension by 1,024 / 64 = 16 times. Suppose, as an invented example, that an icon has a 24-pixel outline in the large file. At 64 pixels, that outline is 24 / 16 = 1.5 pixels wide. A thin line becomes faint on some screens and on a low-resolution print. If an outline looks too light, show the icon larger, or choose a set with bolder lines. Simple shapes survive shrinking better than fine detail.

Remember that worksheets are often printed, sometimes in black and white and sometimes on a cheap printer. Print a test page before you print thirty.

Contrast and colour

Icons need to stand out from their background. The Web Content Accessibility Guidelines 2.2, success criterion 1.4.11 (Non-text Contrast), asks for a contrast ratio of at least 3:1 against adjacent colours for the parts of a graphic that are required to understand the content. It is written for the web, but it is a good rule for any slide or worksheet. If a pale icon sits on a pale page, its outline can fail the test even if it looks charming on your screen.

Two practical habits help. Choose icons with a dark outline and a border, so that they stay visible on light, dark or photographic backgrounds. And do not rely on colour alone for meaning. If a green plate means "biology" and a blue plate means "chemistry", add the word as well, because some learners do not see those colours as you do.

Text alternatives

If a worksheet or slide is shared digitally, some readers will use a screen reader. The W3C's alt decision tree gives a short route to the right answer for each image:

Decorative, or repeating nearby text: use an empty alt attribute, so it is skipped.
Adds meaning: use a short description that conveys that meaning.
Part of a link or button: describe the destination or the action.

A telescope beside a heading that already says "Astronomy" is decorative, and an empty alt is right. A flask that marks "Step 3: mix" is also redundant if the step says "mix", but if the icon alone marks the type of task, give it text. Decide for each use, not once for the whole set.

PNG or SVG

A PNG is a grid of pixels, with transparency. It works in nearly every tool, but it is sharp only up to its own size. An SVG is a vector drawing, described as shapes, so it scales to any size without blur, and many tools let you recolour or edit it. Text inside an SVG may depend on installed fonts, unless it has been converted to shapes.

A practical rule: use SVG when your tool supports it and you want to resize or edit, and PNG when a tool only takes pictures or when you need a quick drop-in. In both cases, test the real size. Export a smaller PNG if the file will be emailed, to keep the document light.

Worked example: planning one worksheet

This is invented, to show the method. A one-page worksheet has 10 questions, in two groups: five on space and five on living things. You decide on two category icons, one for each group, at 1.5 cm, and one small "observe" icon beside the three questions that ask the child to look closely. That is 2 + 3 = 5 icons on the page, not 10, and each has a job. At 1.5 cm and a screen or print of 300 pixels per inch, one icon needs 1.5 / 2.54 x 300 = about 177 pixels, so a 1,024-pixel PNG is more than enough, and about 5.8 times larger than necessary (1,024 / 177).

Then you test. Print the page. Hold it at arm's length. Can a child tell the planet from the leaf? Can they find the "observe" questions at a glance? If not, change one thing, such as making the icons larger, and test again.

A short checklist

Does each icon have a job, and is each job always done by the same icon?
Have you looked at it at the real size and on the real background?
Is there enough contrast between the outline and the page?
Is meaning carried by more than colour?
Does each icon have the right alt text: empty, descriptive or functional?
Does the page still make sense if all icons are removed?
Have you checked the printed version?

Tool that fits

Little Lab Stickers (EUR 9, paid once) is a set of 100 friendly science icons: space (15), biology (16), chemistry (14), physics (14), lab equipment (14), nature (14) and observation (13). Each is a transparent 1024 x 1024 px PNG and an editable SVG, in one style with a dark outline, a colour-coded plate for each group and a white die-cut border, and clear at 64 px. A 100-icon contact sheet PDF and a CSV index with names and keywords help you find the right one. The icons are simplified, symbolic and not to scale, and they are original artwork with no branded characters or logos. Unlimited personal and commercial projects of your own; the files may not be resold or shared.

What to do next

Little Lab Stickers has 100 science icons in seven groups, from space and biology to lab equipment and observation, as 1024 px PNG and SVG, clear at 64 px. €9 once, for your own projects; the files may not be resold.

See the Lab Stickers

Questions people ask

Is SVG always clearer than PNG?

SVG is a vector format, so it can be scaled to any size without blur, and it can be edited. A PNG is a fixed grid of pixels, so it is sharp only up to its own size. At small sizes both can look fine, and some tools accept only PNG, so pick the format your tool handles and test it at the real size.

When does an icon need a text label?

When the meaning is not obvious to a first-time reader. A magnifying glass is widely understood. A tiny drawing of a particular piece of equipment may not be. If a learner might ask "what is that?", add a word. The label also helps anyone who cannot see the picture.

What makes an icon decorative?

An icon is decorative if it adds no information that the surrounding text does not already give. The W3C alt decision tree says to use an empty alt attribute for decorative images, so a screen reader skips them. If the icon carries meaning, such as marking a type of question, give it a short text alternative.

Sources

We checked each source on 17 October 2026. If a fact here is out of date, tell us at hello@hiddenway.info.