Monitor distance calculator
How far should your monitor be from your eyes?
OSHA puts the screen 20 to 40 inches (50 to 100 cm) from your eyes, and never closer than 20 inches. The UK HSE, Cornell University and the American Academy of Ophthalmology (AAO) all say about an arm’s length, which the AAO puts at about 25 inches (64 cm). Within that range, sit where you can read all the text with your head upright, and make the text bigger rather than leaning in. Enter your screen below to see how big it looks from there, how sharp it is, how high to put it and how to angle two screens.
Your screen at 70 cm
27 in, 2560 × 1440
- Viewing distance
- 70.0 cm · 27.6 in
- Within OSHA’s 50–100 cm HSE, Cornell and the AAO put it at about arm’s length.
- Screen size
- 59.8 × 33.6 cm
- 23.5 × 13.2 in picture area, 27-inch diagonal, 16:9.
- Visual angle
- 46.2° × 27.0°
- How wide and tall the screen looks from where you sit.
- Pixels per degree
- 52.3
- At the centre of the screen. Pixel pitch 0.233 mm, 109 pixels per inch.
- Height
- Top ≤ eye level
- Top at eye level (HSE, Cornell), or 1.9 to 8.7 cm · 3.4 in below it to put the centre 15–20° below eye level as OSHA suggests.
- Tilt
- 10–20° back
- So the screen faces your line of sight (OSHA). Watch for ceiling lights reflecting once it is tilted.
What the guidelines say
The main guides agree on the idea and differ a little on the numbers, so the calculator shows them side by side rather than picking one.
| Source | Distance | Height |
|---|---|---|
| OSHA eTool, Monitors | 20–40 in (50–100 cm); at least 20 in | Top line at or below eye level; centre 15–20° below |
| OSHA evaluation checklist | Roughly 18–20 in, or arm’s length | Top at or below eye level |
| HSE (UK) | About an arm’s length | Top of the screen level with your eyes |
| Cornell University | Usually around an arm’s length | Eyes in line with the top of the viewing area; centre about 17–18° below |
| AAO | About 25 in (64 cm), about arm’s length | Gaze slightly downward |
Cornell suggests a quick test: sit back and stretch your arm out; your fingertips should reach about to the screen. OSHA’s two pages give slightly different distances, and the more detailed monitors page is the one the calculator checks against. All of them put comfort first: if you have to lean forward to read, the text is too small or the screen is too far away.
Monitor size for your distance
A bigger screen further away can look the same as a smaller one up close. What your eyes care about is the visual angle: how many degrees of your view the screen covers. The calculator works out the picture’s width from the diagonal and aspect ratio (width = diagonal × 16 ÷ √(16² + 9²) for a 16:9 screen), then the angle as 2 × arctan(half the width ÷ distance).
Pixels per degree says how sharp the screen looks from where you sit: how many pixels fit into one degree of view at the centre of the screen. It rises as you move back and as the resolution goes up. Text and lines look smoother at higher values, and it lets you compare a 4K screen far away with a lower-resolution one up close.
| Screen | Distance | Width seen | Pixels per degree |
|---|---|---|---|
| 24 in, 1920 × 1080 | 60 cm (23.6 in) | 47.8° | 37.8 |
| 27 in, 2560 × 1440 | 70 cm (27.6 in) | 46.2° | 52.3 |
| 32 in, 3840 × 2160 | 80 cm (31.5 in) | 47.8° | 75.7 |
All three fill about the same part of your view, but the 32-inch 4K screen at 80 cm packs twice as many pixels into each degree as the 24-inch Full HD screen at 60 cm. We found no official guideline that sets a best visual angle, so the calculator reports it rather than rating it. If you have to turn your head to read the edges, sit back or choose a smaller screen; OSHA asks for the screen directly in front of you so you don’t twist your head or neck.
Height and tilt
With the top of the screen at eye level, the centre of a 27-inch 16:9 screen at 70 cm sits 13.5° below your eyes. To bring the centre to OSHA’s 15–20°, the top would go between 1.9 cm and 8.7 cm (0.8 and 3.4 in) below eye level, which still fits OSHA’s “at or below eye level”. The calculator works this window out for your screen and distance. Then tilt the screen back by 10 to 20 degrees so it faces your line of sight, as OSHA suggests, and check that ceiling lights don’t now reflect in it.
Glasses. With bifocals or progressive lenses you look through the lower part of the lens, so OSHA suggests lowering the screen below the usual height, raising your chair, or asking about single-vision glasses made for computer work. The AAO describes computer glasses as designed for screens about 20 to 26 inches (51 to 66 cm) away.
Two monitors
OSHA’s checklist puts the main screen directly in front of you, with any others beside it; if you use two screens equally, put them side by side so you need little head movement. The calculator draws the layout from above. For two equal screens it puts the join straight ahead and turns each screen in by arctan(half the screen width ÷ distance), so the middle of each faces you: two 27-inch screens at 70 cm each turn in by about 23°, meeting at about 134°. For a main screen and a second one, the main screen stays straight ahead and the second turns in to face you: a 24-inch screen beside a 27-inch at 70 cm turns in by about 44°.
Common mistakes
- Pulling the screen closer to read small text. Make the text bigger instead; the HSE suggests choosing a text size you can read from a normal, comfortable position.
- A screen that is too high, often on a laptop riser plus a monitor stand, so you look up.
- The screen off to one side, so you work with your head turned.
- Facing a bright window, or sitting with one behind you. OSHA suggests placing the screen at right angles to windows; the HSE suggests blinds and moving the screen to get rid of reflections.
- Brightness left on the factory setting. The HSE suggests adjusting brightness and contrast to suit the lighting in the room.
Buying or setting up a new monitor? Our sister site Flicker Button has a dead pixel test, worth running while you can still return it. Working from a laptop? See how to raise the screen.
General information, not medical advice. If your eyes stay tired, sore or blurry after you have adjusted your screen, see an optometrist or eye doctor: you may need new glasses or treatment for dry eye. The 20-20-20 timer page covers eye strain in more detail.
Sources
All checked on 5 November 2026.
- OSHA Computer Workstations eTool: Monitors and Evaluation checklist.
- Health and Safety Executive (HSE): Good posture when using DSE (updated 20 March 2025), DSE workstation checklist (CK1, 2013) and Working with display screen equipment (DSE): a brief guide (INDG36 rev4, 2013).
- Cornell University Ergonomics Web (Prof. Alan Hedge): Ergonomic guidelines for arranging a computer workstation: 10 steps for users (last revised 13 June 2015).
- American Academy of Ophthalmology: Computers, digital devices and eye strain (27 June 2024) and Eye strain and sleepy eyes (5 May 2023).
- Maths: picture size from the diagonal and aspect ratio by Pythagoras; visual angle 2 × arctan(size ÷ 2 ÷ distance); pixels per degree at the centre 2 × distance × tan(0.5°) ÷ pixel pitch; 1 inch = 2.54 cm.
Questions
How far should a 27-inch monitor be from your eyes?
Within OSHA’s 50 to 100 cm (20 to 40 in), and about an arm’s length for most people. At 70 cm a 27-inch 16:9 screen fills about 46° of your view, much like a 24-inch screen at 60 cm.
Is arm’s length the right distance?
It is a good starting point: the HSE, Cornell and the AAO all use it, and the AAO puts it at about 25 inches. Then adjust until you can read all the text without leaning forward, and enlarge the text if you can’t.
What does pixels per degree mean?
How many pixels fit into one degree of your view at the centre of the screen. It combines resolution, screen size and distance into one number for sharpness, so you can compare screens at different distances.
How high should my monitor be?
With the top of the screen at about eye level, or a little below. OSHA suggests the centre 15 to 20 degrees below eye level and a tilt back of 10 to 20 degrees; with bifocals or progressives, go lower.
How should I set up two monitors?
If one is your main screen, put it straight in front of you and the second beside it, turned in to face you. If you use both equally, put the join in front of you and turn both in, like the two halves of a shallow V.