Calculate screen width and height from diagonal and aspect ratio, or find the diagonal from width and height. Compare TV and monitor sizes in inches or centimeters.
A screen size is usually its diagonal, while aspect ratio describes width compared with height. Choose dimensions-to-diagonal when you can measure both sides, or diagonal-and-ratio when comparing a listed TV or monitor size. Measure the active display area rather than its frame.
Use the active viewing area when comparing a monitor or television. Choose the calculation that matches the measurements you have.
The diagonal is √(24² + 18²) = 30. The same sides are 60.96 × 45.72 cm, with a 76.20 cm diagonal.
Scale both ratio values by 27 ÷ √(16² + 9²). A different aspect ratio changes width and height even when the diagonal stays 27 inches.
These are panel dimensions. Check the product specification for the bezel, stand and mounting clearance. Changing the unit selector reinterprets your input; enter converted values when switching units.
A screen’s advertised size usually describes the diagonal of its viewing area. Choose width and height from diagonal to combine that measurement with an aspect ratio. If you already know the width and height, choose diagonal from width and height instead. For example, a rectangular viewing area 24 inches wide and 18 inches high has a 30-inch diagonal: the square root of 24 squared plus 18 squared.
The calculation follows the Pythagorean theorem. If the ratio is a:b and the diagonal is d, the scale factor is d divided by the square root of a squared plus b squared. Multiplying that factor by a gives width, and multiplying it by b gives height. Panel area is width times height. The formula uses the ratio values as proportions, so 16:9 and 32:18 describe the same shape.
Choose inches or centimeters for the supplied diagonal. Width and height are returned in that unit, with area in squared units and an additional width conversion to centimeters. These are physical dimensions, not pixel counts or a recommendation about viewing distance. Inputs are processed in your browser without uploading a photograph or a room plan.
Choose width and height from diagonal if you know the screen size and aspect ratio. Choose diagonal from width and height if you have measured both sides of the viewing area. Exclude the bezel in either mode.
Match the unit selector to the diagonal value you entered. A 27-inch display requires 27 with inches selected; choosing centimeters changes the meaning of that same number.
For diagonal input, supply horizontal and vertical ratio values such as 16 and 9. For width and height input, enter both measurements in the selected unit; an aspect ratio is not required.
Read width, height and area, then compare them with the space available. Add clearance for the enclosure, stand and cables using actual manufacturer dimensions before purchasing furniture or hardware.
Enter any positive ratio values rather than being limited to a short preset list. Equivalent ratios produce equivalent dimensions for the same diagonal.
The area output uses square inches or square centimeters. It helps compare viewing surfaces, but says nothing about brightness, pixel density or display quality.
An inch is exactly 2.54 centimeters. The secondary width readout uses that conversion, while the primary dimensions retain the selected measurement unit.
An advertised diagonal describes the active screen, not the full monitor or television. The bezel, stand and mounting clearances add space. Use these calculations to compare panel shapes, then check the manufacturer’s physical dimensions before choosing a shelf or desk. Pixel resolution is a separate specification and cannot be inferred from the diagonal alone.
Estimate how much viewing width a candidate monitor provides. Check the manufacturer’s overall size and stand depth separately before assuming it will fit in a constrained space.
Explore why two equally sized diagonals can have different heights and areas. This is useful when comparing a wide video display with a taller reading or document layout.
| Input or option | Reference | What to check |
|---|---|---|
| Diagonal | Corner-to-corner measurement | Not the horizontal width |
| Aspect ratio | Width-to-height relationship | 16:9 and 4:3 yield different dimensions |
| Physical size | Derived display width and height | Compare with mounting or desk space |
Write the active screen width and height as width:height, using the same units, then simplify the ratio. For a 1920 × 1080 resolution with square pixels, divide both numbers by 120 to get 16:9. A viewing area measuring 24 × 18 inches simplifies to 4:3. Enter the ratio values in this screen size calculator together with the diagonal to calculate physical width and height.
Measure the active viewing area horizontally and vertically, excluding the bezel. Divide width by height to find the decimal ratio: 24 ÷ 18 = 1.333…, equivalent to 4:3. Both measurements must use the same unit. A diagonal measurement alone cannot determine aspect ratio; check the product specifications if you only know the advertised screen size.
Combine the diagonal d with the ratio a:b. Width = d × a ÷ √(a² + b²), and height = d × b ÷ √(a² + b²). For a 27-inch 16:9 monitor, the active panel is approximately 23.53 inches wide and 13.24 inches high. Choose Width and height from diagonal and enter 27, 16, and 9 to reproduce the example.
Square the screen width and height, add them, then take the square root: diagonal = √(width² + height²). Use the same unit for both sides. A 24-inch-wide by 18-inch-high display has a 30-inch diagonal. In the tool, select the dimensions-to-diagonal calculation and enter the measured viewing area.
No. Pixel resolution and physical dimensions are separate specifications. Displays with the same pixel count can have different diagonals and therefore different pixel densities. This calculator does not infer resolution from size.
The formula describes a flat rectangle. Curved products may report size in ways that do not match a straight-line desk footprint. Use the manufacturer’s enclosure measurements for space planning rather than relying on this idealized result.
The active panel excludes the surrounding bezel and other hardware. Stands can also extend below or in front of the panel. Those parts are outside the calculation, so the output is not the complete product footprint.
The outputs are rounded to two decimal places, but accuracy also depends on the supplied diagonal and ratio. Advertised sizes may themselves be rounded. Do not treat additional displayed digits as a replacement for an actual product measurement.
An internet connection is required to open tools and refresh a temporary session. Processing stays on your device; the handshake sends a random challenge, not files or text inputs. Libraries, fonts or models may download. Local processing cannot remove risks from an untrusted device or extension.
Divide width and height by their greatest common divisor. For 1920 × 1080 pixels, dividing both by 120 gives 16:9. Pixel aspect ratio does not reveal the physical screen size: many monitor and TV diagonals share that resolution. Use a physical diagonal together with 16:9 to calculate physical width and height.
