What Size Is My Screen in Inches? Check Your Monitor Size
What Size Is My Screen in Inches? Open this page to answer what size is my screen in inches: it shows a Best Guess from your resolution, or enter your own measurement. Use the free viewport size checker online to confirm everything looks correct before you rely on it elsewhere.
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Work Out Screen Size From a Measurement
Measure one edge of the visible screen with a tape measure, pick which edge it is, and we will work out the diagonal in inches (the number on the box).
Asking what size is my screen in inches? The estimator compares your detected resolution and pixel ratio against a small table of known devices to offer a probable diagonal size match, then lets you enter your own measured inches in the manual diagonal field for a number you can actually trust. No browser API can read a screen's physical dimensions, so treat the automatic guess as a starting point rather than a fact, and click Use This Size once you've settled on the real one. Worth knowing before you buy a monitor arm, stand, or privacy filter sized to your exact panel.
Asking what size is my screen in inches sounds simple until you notice the number on the box never matches the width of your desk. Your monitor size is the diagonal size of the lit picture, and once you know it, along with the resolution, you can work out the real width, height and sharpness of any laptop, computer monitor or display, from small 13-inch notebooks to screens anywhere from 13 to 43 inches on a desk.
What Size Is My Screen in Inches? The Diagonal Measurement Explained
Every screen size you see in a listing is measured corner to corner: from one corner of the picture to the opposite corner, never straight across. Only the viewable area counts. The bezel, the plastic or metal frame, and the casing behind it are all left out, so a monitor with chunky borders still has the same rating as a thin-edged one if the visible screen matches. The screen orientation checker tool gives you a clear, actionable result instantly, with no sign-up required.
That single figure is quoted in diagonal inches almost everywhere, even in countries that use metric for everything else. It tells you nothing about shape on its own, which is why the rest of this measurement guide pairs it with aspect ratio and resolution.
How to Measure Monitor Size with a Tape Measure
A flexible tape measure (or a rigid measuring tape for big screens) is all you need. Switch the screen on so the picture edge is easy to see, and keep the tape flat against the glass. The free css breakpoint checker runs entirely in your browser — nothing you enter is ever sent to a server.
Measuring a Desktop Computer Monitor
Start at the top-left corner of the picture and stretch the tape to the bottom-right corner. Read the number where the image ends, not where the frame ends. Measure the lit panel only, round to the nearest tenth, and compare it with the common sizes in the chart below; a reading of 23.7 to 23.8 is a typical "24-inch class" screen.
Measuring a Laptop Screen Without the Bezel
On a laptop screen, open the lid fully and measure across the glass, ignoring the hinge and the touchpad deck. Thin bezels make it easy to over-read by a few millimetres, so start the tape exactly at the first row of pixels. The same method works if you plug in an external monitor and want to compare the two.
Finding My Monitor Size from the Model Number or Product Label
Often you can skip the tape. The model number frequently contains the diagonal: two digits right after the brand letters, such as a "27" or "34" buried in the code. Check the product label on the back, the box, your order history or the manufacturer specs page. For a laptop, search the exact laptop model and look for the "Display" line in its specifications.
Screen Size Calculator Formula for Width and Height
A screen size calculator turns the diagonal \(d\) and the resolution \(w_{px} \times h_{px}\) into real width and height. First find the diagonal in pixels, then scale each side by the ratio of the real diagonal to the pixel diagonal:
$$d_{px} = \sqrt{w_{px}^{2} + h_{px}^{2}}$$ $$\text{Width} = d \times \frac{w_{px}}{d_{px}} \qquad \text{Height} = d \times \frac{h_{px}}{d_{px}} \qquad \text{PPI} = \frac{d_{px}}{d}$$This is exactly what a monitor size checker does behind the scenes. The result is an estimate of the physical inch size, because it trusts the diagonal you enter; the panel itself is never measured by software.
Trigonometry Shortcut for 16:9 Screens
If you know the shape, trigonometry gives a shortcut. For a 16:9 widescreen, the diagonal sits about 29.36° above the bottom edge (the inverse cotangent of 16/9), so width is roughly \(0.8716 \times d\) and height roughly \(0.4903 \times d\).
Worked Example: Physical Size of a 16-Inch 2560×1600 Laptop
Take a 16-inch laptop running 2560 × 1600. The pixel diagonal is \(\sqrt{2560^{2} + 1600^{2}} \approx 3018.9\), so:
- PPI: 3018.9 ÷ 16 = 188.7
- Screen width: 16 × 2560 ÷ 3018.9 = 13.57 in (34.5 cm)
- Height: 16 × 1600 ÷ 3018.9 = 8.48 in (21.5 cm)
- Picture area: 13.57 × 8.48 ≈ 115.1 sq in
Those are the physical dimensions of the picture, and they explain something the label hides: a 15.6-inch 1920 × 1080 laptop is 13.60 in wide, almost the same, but only 7.65 in tall. The 16-inch model's physical size is about 11% larger in picture area purely because of its taller shape.
Diagonal Length from Measured Sides with the Pythagorean Theorem
Sometimes it's easier to measure the sides than the diagonal, for example on a portable monitor with a curved edge. The Pythagorean theorem gives the diagonal length from width \(W\) and height \(H\):
$$d = \sqrt{W^{2} + H^{2}}$$Measure 34.4 cm across and 19.4 cm up, and the diagonal is \(\sqrt{34.4^{2} + 19.4^{2}} \approx 39.49\) cm, or 15.55 in after dividing by 2.54. That rounds to a 15.6-inch screen, and the 34.4 ÷ 19.4 ≈ 1.77 ratio confirms the panel is widescreen.
Sizing a Privacy Filter by Monitor Diagonal When the Label Is Gone
I'm ordering a privacy filter for a shared office monitor whose rear sticker has peeled off. Filters are sold by diagonal and aspect ratio, and the shop offers 23.8-inch 16:9, 24-inch 16:9 and 24-inch 16:10 cuts. The answer, worked out below: the screen is 23.73 inches diagonal at 16:9, so the 23.8-inch 16:9 filter is the one to buy.
With the screen switched on, I measure only the lit picture: 20.69 in across and 11.63 in tall. Measuring the sides is easier here than the diagonal, because the stand's arm blocks the bottom-left corner. Into the calculation they go:
- Diagonal: \(\sqrt{20.69^{2} + 11.63^{2}} = \sqrt{428.08 + 135.26} \approx 23.73\) in
- Shape: 20.69 ÷ 11.63 = 1.779, a hair off 16:9's 1.778
- Cross-check: Windows reports 1920 × 1080 for this screen, which is exactly 16:9, and 2,202.9 pixels across the diagonal over 23.73 in gives about 92.8 PPI, a normal figure for this size class
So the screen size in inches is 23.73, which is how the industry's "24-inch class" panels usually measure. A 23.8-inch 16:9 filter is 20.74 × 11.67 in, within 0.05 in of the picture on each side.
| Filter option | Filter width × height | Overhang vs picture |
|---|---|---|
| 23.8 in, 16:9 | 20.74 × 11.67 in | 0.05 in wide, 0.04 in tall |
| 24 in, 16:9 | 20.92 × 11.77 in | 0.23 in wide, 0.14 in tall |
| 24 in, 16:10 | 20.35 × 12.72 in | 0.34 in short, 1.09 in too tall |
The trap I nearly fell into: my first pass ran the tape over the frame edge, adding about 0.3 in per side. That rerun gives 21.29 × 12.23 in and a 24.55-inch diagonal, which would have pointed me at a 25-inch filter that hangs off the bezel. The input that matters most is where the tape starts, not how precisely you read it.
The 24-inch 16:9 cut would also fit if the clips grip the bezel, but the 16:10 one is the real mistake: same "24-inch" label, over an inch taller than the picture. The diagonal alone can't separate those two; the ratio check is what settles it.
Display Size vs Screen Resolution: Inches Are Not Pixels
Display size is a physical length; screen resolution is the pixel grid, such as 1920 by 1080, 2560 by 1440 or 3840×2160. The two are independent: a 13-inch tablet and a 43-inch TV can share the same pixel count. That's why checking resolution in your settings never tells you the inches, and why a screen size calculator needs both numbers. More pixels on the same diagonal means smaller, finer dots, not a bigger picture.
Pixel Density: PPI at Each Diagonal Size
Pixel density, measured in PPI (pixels per inch), links the two. A 24-inch 1920 × 1200 monitor lands at 94.3 PPI, while the 16-inch laptop above reaches 188.7 PPI, twice the sharpness. Higher density gives sharper text, but the right figure depends on viewing distance: you sit farther from a desk monitor, so a lower PPI still looks crisp. Very dense panels usually need operating-system scaling at 150% or 200% so menus aren't tiny.
How Big Is My Monitor at 16:10 or 21:9? Aspect Ratio Explained
Two screens with the same diagonal can differ a lot in usable picture, so "how big is my monitor" depends on the aspect ratio as well. A 24-inch 16:10 panel is 20.35 × 12.72 in, while a 24-inch widescreen at 16:9 is 20.92 × 11.77 in: slightly wider, nearly an inch shorter. Ultrawide 21:9 screens stretch further, so a 34-inch ultrawide is about as tall as a 27-inch standard model. Older 4:3 screens are the squarest of all and give the most height per diagonal inch.
Screen Size Chart: Common Laptop and Monitor Dimensions
The chart below lists real monitor dimensions calculated with the formula above, in inches and cm, plus the PPI at a typical resolution for each size.
| Diagonal | Ratio / resolution | Width | Height | PPI |
|---|---|---|---|---|
| 13.3 in (33.8 cm) | 16:10, 1920 × 1200 | 11.28 in / 28.6 cm | 7.05 in / 17.9 cm | 170.2 |
| 14 in (35.6 cm) | 3:2, 2256 × 1504 | 11.65 in / 29.6 cm | 7.77 in / 19.7 cm | 193.7 |
| 15.6 in (39.6 cm) | 16:9, 1920 × 1080 | 13.60 in / 34.5 cm | 7.65 in / 19.4 cm | 141.2 |
| 24 in (61.0 cm) | 16:10, 1920 × 1200 | 20.35 in / 51.7 cm | 12.72 in / 32.3 cm | 94.3 |
| 34 in (86.4 cm) | 21:9, 3440 × 1440 | 31.36 in / 79.7 cm | 13.13 in / 33.3 cm | 109.7 |
| 43 in (109.2 cm) | 16:9, 3840 × 2160 | 37.48 in / 95.2 cm | 21.08 in / 53.5 cm | 102.5 |
Is My Monitor Size Right for Your Desk?
Once you know the width, compare it with your desk space. A good desk fit leaves a few inches either side of the stand and puts the screen roughly an arm's length away. For productivity work such as spreadsheets and coding, a wider panel lets you tile two windows; for graphics and photo editing, height and PPI matter more than raw width. A cramped workstation is usually better served by one sharp screen than a large one pushed too close.
What Size Is My Monitor? Popular 24 to 34-Inch Sizes, Ultrawide and 4K
Most desktop screens fall into a handful of sizes, each with a resolution that suits it:
- 24-inch: the compact baseline, usually 1080p (Full HD) for office use
- 27-inch: the popular middle ground, typically 1440p (QHD) for work and gaming
- 27-inch 4K: the sharper option when text clarity matters most
- 32-inch: pairs best with 4K so pixels don't look coarse up close
- 34-inch ultrawide: a 1440p-tall canvas built for multitasking and immersive gaming
Can a Browser Detect Your Screen Size? Viewport, CSS Pixels and DPR
No website can read your physical inches. A browser exposes the viewport (the page area in CSS pixels) and the device pixel ratio (DPR), the number of real pixels behind each CSS pixel. A phone with a DPR of 3 reports a viewport around one-third of its panel width. That's useful for web design and responsive testing, but it can't tell a 24-inch monitor from a 27-inch one at the same resolution, so any online check of inches still needs your diagonal as an input.
Find the Monitor Diagonal in Windows and Mac Display Settings
Neither system prints the size directly, but both point you to it. In Windows, open Display settings, choose Advanced display, and note the monitor name to look up its specs. On a Mac, open the Apple menu, choose About This Mac, then Displays: built-in screens show the diagonal, and external ones show a model name you can search.
Check the Size of a Monitor or TV: LCD, LED and OLED Panels
The rules don't change with technology. An LCD, an LED-backlit LCD and an OLED panel are all rated by the visible diagonal, so you check the size of a monitor or a TV the same way. Large TVs are often listed as "class" sizes, for example a "65-inch class" set that is 64.5 inches of viewable picture, so measure if a wall gap or cabinet is tight.
Check Screen Size on Phone, Tablet and Laptop
To check screen size on phone models and tablets, open the settings page that lists the model name, then look it up; phone diagonals include the rounded corners as if they were square, so the real picture is slightly smaller. On a laptop, the spec sheet or the sticker near the keyboard usually gives it. When in doubt, the tape method above works on any device.
Check Your Monitor Size Before Buying a Mount, Arm or Screen Protector
Accessories are sold by size, so check your monitor size before you order. Monitor arms list a maximum diagonal and weight, TV mounts list a size range and VESA pattern, and privacy filters or screen protectors are cut to an exact diagonal and aspect ratio. Getting the inches right first avoids a return.
Frequently Asked Questions
- How is screen size measured?
- Screen size is the diagonal of the visible picture, measured from one corner to the opposite corner in inches. Width and height are not the rated size.
- Does the bezel count toward my screen size?
- No. Only the lit display area counts. Start and stop the tape where the picture ends, not at the edge of the frame.
- Is screen size the same as screen resolution?
- No. Screen size is a physical length in inches, while resolution is the pixel grid, such as 1920 × 1080. Two screens of different sizes can share one resolution.
- Can a website detect my screen size in inches?
- No. Browsers report pixels, viewport size and device pixel ratio, not physical inches, so you need to enter one real measurement or the size from the specs.
- How do I find my monitor size without measuring?
- Check the model number, the label on the back, the box, your order page or the manufacturer specs. Many model numbers include the diagonal as two digits after the brand letters.
- Are LCD and LED screens measured differently?
- No. LCD, LED and OLED screens, laptops and TVs are all rated by the diagonal of the visible picture.
- Why do I need the aspect ratio to get width and height?
- The diagonal alone doesn't fix the shape. A 24-inch 16:9 screen and a 24-inch 16:10 screen have different widths and heights, so the calculator needs the ratio or your resolution.