ⓘ How accurate is this? — click to expand
This calculator uses user-provided diagonal size and aspect ratio. Results are geometric calculations only — they cannot detect the actual bezel size or measure the true viewable area of your specific display. Manufacturer-listed diagonal sizes are sometimes rounded.
Monitor Dimensions Calculator & Computer Screen Size Calculator
Whether you are setting up a home office, configuring a multi-display desk, or planning a wall mount, knowing the exact screen width and height of your display is crucial.
Using a reliable monitor dimensions calculator makes it easy to find these values. By entering a few basic specifications, you can instantly convert diagonal inches into real-world physical dimensions.
Our free online computer screen size calculator and monitor size calculator support standard, ultrawide, and custom aspect ratios. This tool helps you quickly evaluate screen real estate, surface area, and footprint options before buying a display.
📊 Monitor Size Calculator
Enter the diagonal size and select an aspect ratio to calculate the exact width, height, and area.
How screen size calculations work
Calculating display dimensions from a diagonal measurement relies on simple geometry. The physical size of a monitor is governed by the Pythagorean theorem (a² + b² = c²).
If you know the diagonal screen size and the aspect ratio, you can calculate the exact physical screen width and height using basic trigonometry:
- Step 1: Find the Diagonal Angle: Calculate the angle of the diagonal using the arctangent of the aspect ratio. For example, for a 16:9 screen:
Angle = arctan(9 / 16) ≈ 29.36°. - Step 2: Determine Screen Width: Multiply the cosine of this angle by the diagonal screen size:
Width = cos(29.36°) × Diagonal. For a 27-inch screen:cos(29.36°) × 27 ≈ 23.53 inches. - Step 3: Determine Screen Height: Multiply the width by the aspect ratio fraction:
Height = Width × (9 / 16). For a 27-inch monitor:23.53 × 0.5625 ≈ 13.23 inches.
This formula applies to standard 16:9 widescreen displays, ultrawide 21:9 monitors, and old-school 4:3 CRT screens.
💡 Quick Formula: For 16:9 screens, width ≈ diagonal × 0.8716 and height ≈ diagonal × 0.4903. For 21:9 ultrawide, width ≈ diagonal × 0.9192 and height ≈ diagonal × 0.3939.
Common screen sizes reference table
Here are the calculated dimensions for popular monitor and TV sizes at standard aspect ratios:
| Diagonal | Aspect | Width (in) | Height (in) | Width (cm) | Height (cm) | Area (in²) |
|---|---|---|---|---|---|---|
| 13.3" | 16:9 | 11.59 | 6.52 | 29.4 | 16.6 | 75.6 |
| 13.3" | 16:10 | 11.28 | 7.05 | 28.7 | 17.9 | 79.5 |
| 15.6" | 16:9 | 13.60 | 7.65 | 34.5 | 19.4 | 104.0 |
| 15.6" | 16:10 | 13.24 | 8.27 | 33.6 | 21.0 | 109.5 |
| 24" | 16:9 | 20.92 | 11.77 | 53.1 | 29.9 | 246.2 |
| 27" | 16:9 | 23.53 | 13.23 | 59.8 | 33.6 | 311.3 |
| 27" | 16:10 | 22.90 | 14.31 | 58.2 | 36.3 | 327.7 |
| 32" | 16:9 | 27.89 | 15.69 | 70.8 | 39.8 | 437.6 |
| 34" | 21:9 | 31.25 | 13.39 | 79.4 | 34.0 | 418.4 |
| 49" | 32:9 | 45.56 | 12.81 | 115.7 | 32.5 | 583.6 |
| 55" | 16:9 | 47.94 | 26.96 | 121.8 | 68.5 | 1292.5 |
| 65" | 16:9 | 56.65 | 31.87 | 143.9 | 80.9 | 1805.4 |
Why screen dimensions matter
The physical size of a display affects nearly every aspect of your daily usage. A larger screen with a lower resolution has low pixel density (PPI), making text and images appear pixelated at close range. Conversely, a smaller screen with high resolution delivers crisp images but might require display scaling to keep text readable.
Using a dedicated monitor size calculator is highly recommended when planning multi-monitor desks. It ensures proper alignment by calculating the exact physical screen width and height of different panels beforehand.
Ultrawide (21:9) and super-ultrawide (32:9) monitors typically match the height of standard 16:9 screens in smaller classes. Knowing this lets you configure fluid side-by-side setups without vertical screen misalignment.
Viewing distance and screen size
For comfortable viewing, the ideal screen size depends on how far away you sit. A common recommendation is that the display should fill roughly 30 to 40 degrees of your field of vision.
For standard desk setups, a 27-inch monitor is ideal for a 24-inch viewing distance. For living room TV viewing from 6 to 10 feet away, larger displays in the 55 to 75-inch range work best.
Aspect ratio considerations
Identical diagonal sizes yield very different physical footprints depending on their aspect ratios. For example, a 27-inch 16:10 monitor has about 5% more total surface area than a 27-inch 16:9 display.
A 34-inch 21:9 ultrawide has about 34% more viewing area than a 27-inch 16:9 screen. When comparing options, always look at the physical width and height rather than relying solely on the diagonal measurement.