Monitor Viewing Distance Calculator

Introduction: two different constraints decide how far to sit

Screen distance advice is usually a single number pulled from a rule of thumb, and the rules of thumb contradict each other because they answer different questions. Sitting distance is really governed by two independent constraints, and the sensible answer is wherever they overlap.

The first is optical: how close can you sit before the pixel grid itself becomes visible? That depends only on pixel density, not on screen size. A 27-inch 1080p panel and a 27-inch 4K panel are the same size and want completely different distances.

The second is ergonomic: what distance keeps your neck neutral, your eyes focused comfortably, and the whole screen inside a reasonable sweep of the eyes? The OSHA computer workstation eTool gives a preferred range of 20 to 40 inches, roughly 50 to 100 cm, from the eye to the front surface of the screen.

This calculator computes both and reports where they meet. It deliberately does not use the "one to two times the screen diagonal" rule that circulates for monitors, because that rule comes from television viewing, where the goal is a cinema-like field of view from a sofa. Applied to a 27-inch desk monitor it produces about 43 inches, further than most desks are deep and comfortably outside the OSHA range.

How to use the monitor viewing distance calculator

Four inputs, three of which come straight off the spec sheet.

1. Screen diagonal in inches. The advertised size. If in doubt, measure corner to corner across the visible glass, ignoring the bezel.
2. Horizontal and vertical resolution. Both halves of a spec like 2560 × 1440. Entering both means the calculator derives the true aspect ratio rather than assuming 16:9, which matters a great deal for ultrawide panels.
3. Your current distance (optional). Measure from the bridge of your nose to the front glass while sitting in your normal working posture. Measuring from the desk edge typically overstates it by several inches.

The result gives your panel's pixel density, the distance at which pixels become indistinguishable, where that sits relative to the OSHA band, and the horizontal field of view you end up with. A top-down diagram underneath draws your eye position, the screen, the field-of-view cone, and the shaded ergonomic band, so you can see immediately whether the constraints overlap or fight each other. Units toggle between inches and centimetres, and the address bar updates with a link that reproduces the whole setup.

Formula: pixel density, the acuity limit, and field of view

Pixel density comes from the pixel diagonal over the physical diagonal. With horizontal resolution $R_h$, vertical resolution $R_v$, and diagonal $s$ in inches:

The pixel pitch is the reciprocal, $p=1/\mathrm{PPI}$ inches. A viewer with 20/20 vision resolves detail down to about one arcminute of visual angle, so a pixel stops being individually visible once it subtends less than that. Since one radian is 3437.75 arcminutes, the distance at which a pixel of pitch $p$ subtends exactly one arcminute is:

with the result in the same unit as the pitch. Note what is absent: the screen diagonal cancels out of the ratio in every place except through PPI, so two panels with the same pixel density want the same distance regardless of how large they are.

Physical screen width follows from the diagonal and the pixel aspect ratio, since desktop panels use square pixels:

and the horizontal field of view at a viewing distance $d$ is a straightforward bit of trigonometry:

The recommendation is then the acuity distance clamped into the ergonomic band:

When $d_{\mathrm{acuity}}$ falls inside the band, the two constraints agree and you have a clean answer. When it exceeds 40 inches, the panel is too coarse to hide its pixels at any ergonomic distance, and no amount of desk rearranging fixes it. When it falls below 20 inches the panel is denser than your eyes can exploit at a desk, which is fine: you can sit at the near end of the band and simply never see a pixel.

Worked example: a 27-inch 1440p panel on a normal desk

Take the most common enthusiast desktop configuration, a 27-inch panel at 2560 × 1440. The pixel diagonal is:

so the density is 2937.2 / 27 = 108.8 PPI, and the pitch is 1/108.8 = 0.00919 inches (0.233 mm). The acuity distance follows:

That sits comfortably inside the 20 to 40 inch ergonomic band, so 31.6 inches is the recommendation with no compromise required. The screen is 27 × 2560/2937.2 = 23.5 inches wide, giving a horizontal field of view of 2 · arctan(23.5 / 63.2) = 40.8°, which is a comfortable productivity angle: the whole panel is inside the sweep of your eyes without head movement.

Contrast that with a 27-inch panel at 1920 × 1080, a configuration many people buy because it is cheap. The density drops to 81.6 PPI and the acuity distance rises to 42.1 inches, outside the ergonomic band. There is no seating position that is both comfortable and pixel-free. The old rule of thumb would have told you to sit 43 inches away and would have been accidentally right about the number while being wrong about the reason and impossible to act on. The real answer is to raise display scaling so glyphs are drawn from more pixels, or to buy a denser panel.

Reference distances for common panels

Every row below is computed with the formulas above, not estimated. The recommended column is the acuity distance clamped into the OSHA band, and the field of view is measured at that recommended distance.

Two patterns stand out. Pixel density, not size, drives the distance: the 27-inch 1440p, the 34-inch ultrawide, and the 49-inch superultrawide all land within half an inch of each other because all three are near 109 PPI. And field of view, not distance, is what makes very wide panels tiring: at 73° the far edges of a 49-inch screen sit outside the range your eyes can reach without turning your head.

Reading the result and adjusting your setup

If your current distance is inside the recommended band, nothing needs to change. If it is shorter, the usual cause is text that is too small: people lean in rather than change scaling. Raise the display scaling or font size one step and see whether you naturally sit back. If it is longer, check the screen height first, since a monitor that is too high pushes people back and up into chin-jutting posture more often than distance alone does.

The field of view number is worth a second look on large or ultrawide panels. Below roughly 40° the whole screen is inside a comfortable eye sweep. Between 40 and 60° you will move your eyes a lot but rarely your head. Above 60° head movement becomes constant, which is why superultrawides are usually curved and placed further back than their pixel density alone would suggest.

Distance is only one of several ergonomic variables, and it is not the one people most often get wrong. Keeping the top of the screen at or just below eye level, eliminating glare from windows behind you, and taking periodic distance-focus breaks all matter at least as much as the exact number of inches.

Limitations and assumptions in this model

The optics here are exact; the assumptions surrounding them are where the answer can drift from what feels right.

• Display scaling and font size are not modelled, and this is the largest gap. The acuity distance says when pixels become invisible, not when text becomes readable. At 150% scaling each glyph is drawn from far more pixels and remains legible much further away than raw pixel geometry implies.
• 20/20 vision is assumed. One arcminute is the standard threshold, but real acuity varies widely. Someone with 20/15 vision resolves finer detail and would need to sit further back to hide the same pixels; a presbyopic viewer in progressive lenses has a preferred focal range that may override everything here.
• Subpixel rendering is ignored. Text antialiasing that addresses individual RGB subpixels effectively triples horizontal resolution for edge placement, so text can look smooth at distances where a test pattern would still show structure.
• Flat geometry. The field-of-view calculation treats the panel as flat and measures to its centre. On a curved monitor the edges are nearer than the formula assumes, which is precisely why curves are used on wide panels.
• The OSHA band is a general workstation guideline. It is not a per-person prescription, and it assumes a seated desk posture. Standing desks, laptops on laps, and lounge setups all fall outside its scope.
• Single-monitor geometry. Multi-monitor arrays place secondary panels at an angle, so effective distance and viewing angle differ per screen and neither is captured here.
• Not medical advice. Persistent headaches, eye pain, or neck problems warrant an optometrist or an occupational health assessment rather than a calculator.

Questions people ask about screen distance