Monitor Size Calculator: Free Screen Size Calculator
Monitor Size Calculator. Enter a Screen Diagonal and aspect ratio in this monitor size calculator to get your screen's Width, Height and Screen Area. To compare screen sizes for a multi-monitor setup, enter each panel's diagonal and ratio to see the combined desk footprint.
Interactive Tool
Diagonal → Width × Height
In centimeters: 59.8 cm wide × 33.6 cm tall, 2010.0 sq cm area.
Width × Height → Diagonal
68.5 cm diagonal.
Compare With a Second Screen
Enter a screen diagonal and aspect ratio and this monitor size calculator works out the physical width, height, and screen area in inches and centimeters — or work backwards from width and height to find the diagonal size and detected aspect ratio.
A listing that says "31.5 inches" tells you the diagonal, not how wide the panel is or whether it fits under your shelf. The monitor size calculator turns that one number plus an aspect ratio into the real height and width, the area and the pixel density, so you can compare a display, a TV or phone screen dimensions before you buy. Add the pixel resolution and it also shows how sharp the image size will look from your chair.
How the Screen Size Calculator Works
The online screen size calculator needs only two inputs for a standard panel, and a third for a curved one. The rest is exact geometry.
- Choose the aspect ratio from the drop-down menu, or pick custom and type both sides of the ratio yourself.
- Enter the diagonal in inches or centimetres, as printed on the spec sheet.
- Set the screen shape to flat or curved; a curved display also asks for its curvature.
- Read the width, height and area of the screen size you entered, plus the pixel figures if you added a resolution.
Picking Your Aspect Ratio and Diagonal
The aspect ratio is the width-to-height ratio of a rectangular display. It describes proportion only: 16:9, the widescreen standard, says the panel is 16 units wide for every 9 tall in landscape orientation, but nothing about how big it is.
Monitor Size Calculator Formula: Width and Height from the Diagonal
The diagonal, width and height form a right triangle, so the Pythagorean theorem links them. With the ratio written as one number, \(AR = \frac{W}{H}\), the height comes first: Use the tv size calculator to find the largest TV size that still looks sharp from your sofa position given its resolution.
$$H = \frac{D}{\sqrt{AR^{2} + 1}} \qquad W = AR \times H \qquad A = W \times H$$Worked example: a 31.5-inch 16:9 panel has \(AR = 1.778\), so \(\sqrt{1.778^{2} + 1} = 2.040\). The screen height is 31.5 ÷ 2.040 = 15.44 in (39.2 cm), the width is 1.778 × 15.44 = 27.45 in (69.7 cm), and the area is 424 sq in. That is the whole job of a screen width and height calculator.
How to Measure Diagonal Screen Size by Hand
Run a measuring tape from one corner of the visible picture to the opposite corner, ignoring the bezel. To check the screen's diagonal against a spec, measure the height and width, add their squares and take the square root: 27.45² + 15.44² gives 31.5 again, the same answer a diagonal screen size calculator returns.
Screen Area from Width and Height
Multiply width by height for the screen surface. Two panels with the same diagonal measurement can differ by more than 100 sq in, which a screen dimensions calculator makes obvious.
Screen Size by Aspect Ratio: 16:9 vs 21:9 vs 16:10 vs 4:3
Keep 31.5 inches fixed and change only the ratio, and the panel changes shape and area. An aspect ratio screen size calculator shows the trade-off at once:
| Aspect ratio | Width (inches) | Height (inches) | Area (sq in) |
|---|---|---|---|
| 16:9 | 27.45 | 15.44 | 424 |
| 21:9 ultrawide | 28.95 | 12.41 | 359 |
| 16:10 | 26.71 | 16.69 | 446 |
| 4:3 | 25.20 | 18.90 | 476 |
The wider the ratio, the less area you get. A gaming monitor in a stretched format suits films and racing games, but standard video shows letterboxing bars at the sides, and a TV signal stretched to fill it means cropping. A laptop with a taller ratio gains vertical room for documents.
Viewable Area of a Curved Monitor: Curvature Rating and Base Width
A curved monitor uses the same diagonal and ratio, but its panel bends along a circle. The curvature rating gives that circle's radius in millimetres: 1800R means 1,800 mm, and 1500R is a tighter 1,500 mm. Treat the flat width as the arc length \(L\) and the radius as \(R\):
$$W_{base} = 2R\sin\left(\frac{L}{2R}\right) \qquad d_{base} = R\left(1 - \cos\frac{L}{2R}\right)$$For the same 31.5-inch panel bent to 1500R (59.06 in), the base width is 27.21 in and the base depth is 1.59 in.
Why a Curved Screen Takes Less Desk Width
The bend pulls the edges in about a quarter inch but pushes the corners toward you. Plan your desk width from the base width, and add the base depth to the stand depth.
Checking Display Size for an Ultrawide in a 36.6-Inch Speaker Gap
I mix podcasts on a desk where two studio monitors sit on stands exactly 36.6 in apart, inner edge to inner edge. The speakers can't move without wrecking the stereo image, so the question is narrow: will a 37.5-inch 24:10 ultrawide fit between them, and is it really bigger than the two 23.8-inch 16:9 screens I use now? The short answer is yes on both counts, though by less than the diagonal suggests.
I start with the current pair. Entering 23.8 in and 16:9 returns 20.74 in wide by 11.67 in tall, 242 sq in each. Side by side with a 0.9 in bezel seam, they span 42.38 in, which is why they already hang past the speakers.
Then the candidate: 37.5 in, ratio set to custom 24:10. The calculator divides 37.5 by \(\sqrt{2.4^{2}+1} = 2.6\) and returns 34.62 in wide, 14.42 in tall, 499 sq in. I check it by hand: 34.62² + 14.42² = 1,406.5, and its square root is 37.50. With about 0.4 in of bezel per side, the panel needs 35.4 in, leaving 1.2 in of air in the gap.
| Setup | Width | Height | Area |
|---|---|---|---|
| Two 23.8 in 16:9 | 42.38 in | 11.67 in | 484 sq in |
| 37.5 in 24:10 flat | 34.62 in | 14.42 in | 499 sq in |
| 37.5 in 24:10 at 2300R | 34.41 in | 14.42 in | 499 sq in |
Solving backwards, the largest 24:10 panel that clears the gap with 0.8 in of bezel is a 38.78-inch diagonal, so a 37.5 in model is the right class and a 40 in one is not.
The number I watch is height, not area. The ultrawide adds 2.75 in of height, but that is only 1.18 in more than a single 27-inch 16:9 panel at 13.24 in. Comparing diagonals across different ratios misleads; compare heights instead.
One caveat comes from the calculator's sharpness result: 3840 x 1600 on 37.5 in works out to 110.9 pixels per inch, and the 1/60° acuity limit puts pixel visibility at 31.0 in. I sit 27.6 in away, inside OSHA's 20 to 40 inch workstation range but close enough to see the pixel grid on fine waveform lines. I'll accept that, because the bigger risk was the speakers, and the 1.2 in of clearance answers it.
Pixel Density and Screen Area
Once you know the size, the pixel count decides sharpness. Pixels per inch divides the pixel count along the corners by D:
$$PPI = \frac{\sqrt{p_w^{2} + p_h^{2}}}{D}$$At 4K (3840 x 2160), our 31.5-inch panel holds 8.29 megapixels at 139.9 PPI, a pixel size of 0.18 mm. The same panel at full HD (1920 x 1080) drops to 69.9 dots per inch. DPI and pixels per inch mean the same thing for screens; a phone with a Retina panel passes 300. A ppi calculator runs the same sum.
Matching Source Resolution to the Panel
Higher pixel density gives sharper images only when the source resolution matches. Low-detail content stretched across a big, dense panel shows pixelation and soft edges.
Viewing Distance and Image Size
Size depends on viewing distance. Two rules set the range. Visual acuity: the eye resolves about 1/60 of a degree, so on the 4K display above single pixels disappear beyond about 24.6 in. Field-of-view: for an immersive 30° viewing angle, sit about 51 in from a 27.45-inch-wide panel. A tv screen size calculator applies the same maths to the living room and home theater.
Ideal Viewing Distance for a Desk Monitor
Take the width the calculator returns and check your seat against it. For office work, an arm's length of 20 to 30 in avoids eye strain and turning your head, and it should sit between the acuity and field-of-view distances above. Push a large screen too far back and you waste the viewing experience.
Display Size Calculator Uses: Phones, Projectors and Multi-Monitor Setups
The same width and height formula sizes a smartphone, a tablet or a projector image: a 100-inch 16:9 picture comes out 87.2 in wide and 49.0 in tall. A projector screen size calculator adds throw distance on top, and an aspect ratio calculator handles the ratio alone, but every display size calculator rests on this geometry. This free screen size calculator gives you both numbers for gaming or productivity setups.
Planning a Dual Monitor Setup
Add the widths of each panel plus about 1 in of bezel between them. Match the heights too, or your cursor jumps when it crosses from one screen to the next in a multi-panel monitor setup.
Frequently Asked Questions
- How do I calculate a monitor's width and height from its diagonal?
- Turn the aspect ratio into one number (16:9 is 1.778), then divide the diagonal by the square root of that number squared plus one to get the height. Multiply the height by the ratio to get the width. A 31.5-inch 16:9 monitor works out to 15.44 in tall and 27.45 in wide.
- How do I measure diagonal screen size?
- Measure from one corner of the visible picture to the opposite corner, leaving out the bezel. If you only have the width and height, square both, add them and take the square root.
- How do I calculate screen area?
- Measure the width and height in the same unit and multiply them. Area is the better way to compare panels with different aspect ratios, because two screens with the same diagonal can have very different areas.
- How big is a 16:9 screen?
- It depends on the diagonal, since 16:9 only fixes the shape. Multiply the diagonal by 0.872 for the width and by 0.49 for the height, then multiply width by height for the area.
- How do you measure a curved monitor?
- Measure the diagonal along the curved surface, just like a flat screen. The curvature rating gives the radius in millimetres (1800R is 1,800 mm), and the calculator uses it to work out the straight-line base width and how far the curve sticks out, the base depth.
- Why does aspect ratio change the screen size?
- With a fixed diagonal, a wider ratio gives you more width but less height and less total area. A 21:9 ultrawide is wider than a 16:9 panel with the same diagonal, but shorter and smaller overall.
- How far should I sit from my monitor?
- For desk work, about an arm's length (20 to 30 in) suits most monitors. Sharper, higher pixel density panels let you sit closer before individual pixels become visible.