How to use this screen size calculator
- Enter the diagonal for Screen A and choose the unit printed in its specification. A screen diagonal runs from one corner of the active picture to the opposite corner; it is not the complete width of the product.
- Enter the width and height parts of its aspect ratio. Common examples are 16:9 for many TVs and monitors, 16:10 for some laptops, 21:9 for ultrawide monitors, and 4:3 for older or specialized displays. Custom positive ratios are accepted.
- Repeat the same entries for Screen B. The units do not need to match: you can compare a 27-inch monitor with a 68.58-centimeter display because the calculator normalizes both before comparing them.
- Read each screen’s active width, active height and active area. Then use the signed differences and area percentage to understand how Screen B changes from Screen A.
- Use the shared-scale outlines to check shape and relative size at a glance. Treat the listed measurements—not the number of pixels shown on your browser—as the planning values.
What the comparison means
A diagonal is only one length. Two displays with the same diagonal can have different widths, heights and areas when their aspect ratios differ. The calculator therefore derives the two sides before comparing area. Active area is width multiplied by height and is a useful way to describe the amount of rectangular viewing surface.
The percentage uses Screen A as the baseline: (area B − area A) ÷ area A × 100. A positive value means B has more active area, a negative value means B has less, and zero means the calculated rectangles are equal. Width and height differences remain signed because a wider ultrawide screen can also be shorter than another screen.
Both outlines use one mathematical scale and baseline, preserving relative geometry. They do not calibrate your browser, monitor, zoom or device pixel ratio, so do not measure them with a ruler.
How width and height are calculated
For a diagonal d and aspect ratio w:h, the ratio diagonal is √(w² + h²). Active width is d × w ÷ √(w² + h²), and active height is d × h ÷ √(w² + h²). The same unit follows through both results.
The calculator converts centimeters to inches with 1 inch = 2.54 centimeters for the internal comparison, then shows both inch and centimeter measurements. Squaring that conversion gives 1 square inch = 6.4516 square centimeters. Displayed values are rounded for readability while the comparison uses unrounded numbers.
Worked screen comparisons
55-inch versus 65-inch 16:9 TVs
A 55-inch 16:9 active rectangle is about 47.94 inches wide, 26.96 inches high and 1,292.58 square inches. A 65-inch model at the same ratio is about 56.65 by 31.87 inches and 1,805.34 square inches. Screen B is 10 inches larger diagonally and has about 39.67% more active area—not merely 18.18% more—because area grows in two dimensions.
27-inch 16:9 monitor versus 34-inch 21:9 ultrawide
A 27-inch 16:9 display is about 23.53 by 13.24 inches with 311.50 square inches of area. A 34-inch 21:9 display is about 31.25 by 13.39 inches with roughly 418.50 square inches. The ultrawide gains about 7.72 inches of width but only about 0.15 inch of height, illustrating why diagonal alone can hide the practical shape difference.
When this calculator is useful
Use the width and height to estimate whether an active picture suits a wall opening, cabinet view, desk layout or multi-monitor arrangement. For physical fit, add the manufacturer’s bezel, case, stand and mount dimensions separately; those are product dimensions rather than screen dimensions.
Area and the outline help compare TVs, monitors, laptops, tablets, handheld displays or projector image rectangles across different aspect ratios. Resolution is deliberately absent: a larger area does not imply more pixels or sharper text, and a smaller high-resolution panel can have higher pixel density.
Keep the copied comparison with the exact model specifications, and recalculate if a nominal diagonal is rounded.
Limits and common input errors
- The geometry assumes a flat rectangle. Curved panels, rounded corners, cutouts and foldable or irregular displays can have a smaller visible area than the rectangular estimate.
- Do not type units, quote marks or a colon inside number fields. Choose the diagonal unit separately and put the two ratio components in their own boxes. A decimal point or comma is accepted, but thousands separators and exponent notation are not.
- An aspect ratio is a proportion, so 16:9 and 1.777778:1 describe almost the same shape. Rounding a published ratio can create a small difference. Use the manufacturer’s active dimensions when installation tolerances are tight.
- The tool does not detect the current device, identify a model, recommend a viewing distance, calculate PPI, or promise a life-size preview. It also does not decide which screen is better for a task.
Copying and using the result
Copy comparison creates a plain-text summary of both active rectangles and the area change. Paste it into a note or specification worksheet. Save the model numbers and manufacturer dimensions alongside it because the calculator cannot verify the source specification.
Frequently asked questions
Does screen size include the bezel?
No. Screen diagonal normally describes the active picture. Use the manufacturer’s complete product width, height and depth when checking a shelf, wall, stand or bag.
Why is the area increase larger than the diagonal increase?
For screens with the same ratio, width and height both scale with the diagonal, so area scales with the diagonal squared. A modest diagonal increase therefore produces a larger percentage increase in area.
Can I compare inches with centimeters?
Yes. Select the correct unit for each diagonal. Both are converted to one internal unit before dimensions and differences are calculated.
Are the outlines shown at actual physical size?
No. They share a proportional scale with each other, but the page is not calibrated to your screen or browser zoom. Use the numeric dimensions for measuring.
Does a larger calculated area mean better image quality?
No. Image quality also depends on resolution, pixel density, panel technology, content, viewing distance and other factors that this geometry tool does not evaluate.