Viewing Distance Calculator

Calculate a viewing distance from your screen diagonal, aspect ratio, and the horizontal viewing angle you want.

Go to test controls

This calculator runs on this page using only the values you enter. How accurate is this test?

Before you start

  • Measure the screen diagonal rather than estimating it.
  • Enter the native resolution to supply the screen aspect ratio, and measure from your eyes to the screen.
Step-by-step instructions

How to run this check

  1. Open Viewing Distance Calculator
  2. Enter your screen size (inches)
  3. Enter the native resolution to supply the screen aspect ratio
  4. Choose a horizontal viewing angle and optionally enter your measured distance
  5. Compare the calculated distance with your desk depth and adjust for comfortable reading

How large will the screen look from your seat?

A screen has a physical width and an apparent angular width. This calculator connects those two quantities: choose a horizontal angle to calculate a distance, or enter your measured distance to find the angle the screen occupies. The 30°, 40°, 50°, and 60° buttons are comparison examples you can change, not recommended or medically safe viewing targets.

The model assumes a flat rectangular screen, square pixels, and a viewer centered straight in front of it. A curved screen, an off-center seat, or a tilted screen needs different geometry. The calculator does not save or upload your entries.

Enter the screen and a comparison

Use the viewable panel diagonal, excluding its bezel. Size buttons change only this input.

Choose the panel's native pixel dimensions. Their ratio determines physical width; the pixel count also supplies PPI. Selecting another resolution with the same aspect ratio changes PPI, not viewing geometry.

A larger angle means the same screen occupies more of your view and the calculated distance is shorter. These are illustrative preferences; 40° is simply the initial example.

Measure from your eye position to the screen center, not from the desk edge. This adds the actual horizontal angle at your current position.

Enter the screen diagonal to calculate. The result describes geometry, not a universal best distance.

The triangle behind the numbers

Imagine looking down on a flat screen and your seated eye position. Draw lines from your eyes to the left and right edges. The angle between those lines is the horizontal angle, θ. Split that triangle down its center: the opposite side is half the screen width, W/2, and the adjacent side is distance D.

Top view of a flat screen and a centered viewer The screen width W forms the top of a triangle. A centered eye is distance D from the screen. Lines from the eye to the screen edges enclose the full horizontal angle theta. Diagram is not to scale. Screen width WDθCentered eye position
1. Diagonal to physical width
W = diagonal × pixel width / √(pixel width² + pixel height²)
2. Desired angle to distance
D = W / (2 × tan(θ / 2))
3. Measured distance to actual angle
θ = 2 × arctan(W / (2 × D))

Use the same length units for W and D. Angles displayed here are degrees; the calculation converts to radians for the JavaScript trigonometric functions. These are applications of the opposite/adjacent tangent relationship in OpenStax's right-triangle trigonometry reference.

Worked example: a 27-inch 2560 × 1440 screen

These are calculated example dimensions, not measurements of a particular monitor. A 27-inch 16:9 rectangle is 23.53 inches (59.77 cm) wide. At an illustrative 40° horizontal angle, the equation gives 82.1 cm. At a measured 70 cm instead, that same screen occupies 46.2°.

30° example: 111.5 cm from your eyes to the screen.

40° example: 82.1 cm from your eyes to the screen.

50° example: 64.1 cm from your eyes to the screen.

60° example: 51.8 cm from your eyes to the screen.

The 40° calculation is 59.77 / (2 × tan(20°)) ≈ 82.1 cm. This does not tell you to move to 82.1 cm: it tells you what that chosen angle implies. If your measured position is 70 cm, moving about 12 cm farther away would make the screen occupy a smaller horizontal angle. Whether that is useful depends on the task and whether you can still read the content.

Change only the selected resolution to 1920 × 1080 while keeping the diagonal and 16:9 shape: the calculated width and all angle distances stay the same. PPI changes from about 109 to 82. Pixel count changes how much detail can be represented; it does not physically widen this screen or determine one correct seat position.

Turn the calculation into a desk comparison

  1. Record the current arrangement. Sit as you normally work and measure from your eyes to the screen center. Note the screen size, selected resolution, OS scaling, and app zoom. Desk depth alone omits your seated position and the monitor stand.
  2. Pick one comparison, not a target to pass. Use a second measured distance you can actually fit on the desk, or calculate the distance for a different angle. Check the stand, keyboard, and chair clearance before moving anything.
  3. Use the same task at both positions. Read the same paragraph, inspect the same image detail, or use the same spreadsheet columns. Keep app zoom unchanged for this first comparison. Note when you lean forward to read or turn farther to reach the screen edges.
  4. Separate text size from screen size. If text becomes hard to read farther away, compare an increase in app text size or OS scaling as a separate change. The text samples give you a repeatable reference. Changing text size alone does not change these geometric angles or distances.
  5. Keep the useful arrangement and stop. Record the distance and settings that work for your task. A calculated angle cannot establish comfort, eyesight, posture, or medical safety, and there is no score to maximize.

CCOHS's monitor-positioning guidance treats workstation recommendations as starting points to adapt to the person and emphasizes readable text. Its monitor placement angle above or below eye level is different from this calculator's left-edge-to-right-edge horizontal angle. The guidance does not endorse our example angles.

Background

Viewing distance, field of view, and visible detail

How far you sit decides two different things: how much of your vision the screen fills, and whether you can see individual pixels. The calculator above handles the first with simple geometry. The sections below cover the second, along with common reference points from cinema and workplace guidance.

Field of view reference points

The horizontal angle the screen fills is set by its width and your distance. Film and home-theater guidance gives a sense of scale. SMPTE has recommended a viewing angle of at least 30° for cinema screens, and THX recommends around 36–40° from the back row for an immersive picture. A desk monitor is often closer to 40–60°, which suits work where you move your eyes and head across documents. These are reference points, not rules; reading, gaming, and watching films each suit different angles.

When pixels stop being visible

Normal visual acuity (20/20) resolves detail of about one arcminute, 1/60 of a degree. The distance beyond which neighboring pixels blend together is 1 ÷ (PPI × tan(1/60°)), roughly 3,438 ÷ PPI inches. Closer than that, a sharp eye can in principle see pixel structure; further away, extra resolution adds little visible sharpness.

Approximate distance at which pixels blend for 20/20 vision
ScreenPPIDistance
24-inch 1920 × 108091.8about 37 in (95 cm)
27-inch 2560 × 1440108.8about 32 in (80 cm)
27-inch 3840 × 2160163.2about 21 in (54 cm)

Workplace guidance

Ergonomic guidance for office monitors, such as OSHA’s computer workstation guidelines, suggests placing the monitor at least 20 inches (about 50 cm) from your eyes, often 20–40 inches, with the top of the screen at or slightly below eye level. Larger screens generally need more distance so you are not turning your head constantly. If you find yourself leaning in to read, increasing text scaling is usually better than moving the screen closer.

Putting it together

  • Use the calculator to find the distance for the field of view you want.
  • Compare it with the pixel-blending distance above. If you sit much closer, text rendering and scaling matter more.
  • Check the result against your desk depth and posture. A monitor arm can add useful flexibility.

Common questions

Does sitting close to a screen damage your eyes?
For adults, there is no good evidence that close viewing causes lasting damage. It can cause eye strain and dry eyes, mostly because people blink less while concentrating, and regular breaks help: a common suggestion is to look at something about 20 feet away every 20 minutes or so. In children, a lot of close-up work and little time outdoors are linked to faster progression of nearsightedness.
Why do curved monitors change the recommended distance?
A curve brings the edges closer to your eyes and turns them toward you. It reduces the off-angle viewing at the sides on wide screens, which lets you sit a little closer comfortably.
Is a 4K monitor wasted at normal distance?
Not for text. Even beyond the pixel-blending distance, higher density makes letters smoother because each character is drawn with more pixels. For video and games, the visible difference shrinks with distance.

How accurate is this test?

What it shows reliably

  • Geometric distance from the entered screen diagonal, resolution aspect ratio, and chosen horizontal viewing angle; the angle at an optional measured distance.

What needs a measuring instrument

  • Personal comfort, eyesight, and posture still decide the final distance; an eye-care professional can advise on visual strain.

Reading your result

  • The chosen angles are comparison examples, not a recommended viewing-distance range. Check actual text readability and desk space.
  • Resolution supplies the aspect ratio. At the same diagonal and aspect ratio, additional pixels change PPI but not the geometric distance.
  • Exact physical placement requires a tape measure; individual ergonomic assessment requires a qualified professional.
Recommended setup and sources

Recommended setup

  1. Enter the display diagonal and native resolution accurately; the model assumes a flat screen and square pixels.
  2. Measure from your eyes to the screen rather than to the desk edge.

Sources

Methodology reviewed: