Screen Ratio Calculator - Width, Height and Diagonal Size

A Screen Ratio Calculator turns the physical width and height of a monitor, television or phone panel into the same simplified W:H ratio that designers and spec sheets use. Type the screen width and height in inches and the calculator returns the reduced screen ratio (such as 16:9 or 4:3), the diagonal screen size in inches and centimetres, and a match against common display standards.

• • Verifying a TV or monitor listing: Confirm a manufacturer's '32 inch class' claim by checking the actual width and height against the diagonal.
• • Naming the panel on a spec sheet: Pick the right standard name (16:9, 16:10, 4:3, 21:9) without reducing fractions manually.
• • Comparing two monitors before a purchase: Compute diagonal size and centimetre dimensions of two panels to decide which fits a desk mount.
• • Planning a video wall or kiosk layout: Match screen dimensions in centimetres to a CAD drawing so frames and bezels line up.

Most confusion around screen sizes comes from mixing up diagonal size (the marketing number) with the width and height you need for mounting and bezels. The calculator works in physical inches and returns everything else from that one pair of inputs.

Output is phrased in both inches and centimetres because panel specifications, mount cutouts and CAD drawings rarely agree on units. The same numbers drop straight into a spec sheet or vendor quote.

When the source dimensions are stored as CSS pixels rather than physical inches, the CSS Aspect Ratio Calculator is the natural next step because it converts pixels into the same simplified W:H pair plus a copy-ready aspect-ratio snippet.

The calculator takes the two physical dimensions, divides width by height to get a decimal ratio, then reduces both numbers by their greatest common divisor so the pair is the simplest whole-number form, and finally applies the Pythagorean theorem to compute the diagonal size.

• width: Horizontal edge of the panel in inches (bezel excluded).
• height: Vertical edge of the panel in inches (bezel excluded).
• gcd: Greatest common divisor of the two scaled dimensions, used to reduce the ratio to the smallest whole-number pair.
• decimalRatio: Width divided by height, shown to four decimal places for direct comparison with preset standards.
• diagonal: Square root of width squared plus height squared; matches the diagonal measurement used on monitor and TV spec sheets.

Reducing the ratio with the greatest common divisor turns 1920 by 1080 pixels into the clean 16:9 pair designers write down. The same reduction works on physical inches scaled to integers.

The diagonal calculation uses the Pythagorean theorem on the two inch values, producing the same diagonal regardless of orientation. Multiplied by 2.54, the result becomes the metric equivalent mount spec sheets and CAD drawings usually expect.

According to W3C CSS Sizing Module Level 4, aspect-ratio property accepts a positive <ratio> written as W / H, which is the same notation used for screen ratios.

When you need the pixels-per-inch of the same panel, the Screen Resolution Calculator converts width, height and diagonal size into PPI and optimal viewing distance in one step.

Four ideas that explain why a clean integer ratio and a single diagonal number cover most of what a screen spec sheet actually needs.

Each of these concepts shows up in the calculator: the GCD makes the simplified pair small, the decimal value bridges to the preset list, and the diagonal tells you whether a '27 inch' label means a flat 16:9 panel or a tall 16:10 productivity display.

Because the calculator reports both inch and centimetre values, you can compare panels across vendors without redoing conversions. The unit pair also confirms a vendor quote against a metric CAD drawing.

According to ITU-R BT.709, 16:9 is the international standard for high-definition television with a 1920x1080 raster, which is why broadcast, streaming and panel manufacturers all adopt the same 16:9.

When the GCD reduction needs to run on a ratio that is not inches, the Simplify Ratio Calculator applies the same algorithm to any pair of numbers and returns the simplest form.

Five quick steps from a tape measure or spec sheet to a named ratio plus diagonal size and centimetre dimensions.

1. 1 Measure the screen width: Measure the horizontal edge of the viewable area in inches with the bezel excluded. Enter the value in the Screen Width field.
2. 2 Measure the screen height: Measure the vertical edge of the viewable area in inches. Enter the value in the Screen Height field.
3. 3 Read the simplified ratio: The Simplified Screen Ratio result is the smallest whole-number form that preserves the input ratio.
4. 4 Check the closest standard: Confirm the Closest Standard result. A 16:9 widescreen match means the panel follows the television and Full HD default.
5. 5 Use the diagonal and centimetre outputs: Copy Diagonal Size for spec sheets and the centimetre values for metric drawings or vendor quotes.

A 27 inch class 16:9 monitor measures 23.53 in wide by 13.24 in tall. Typing those values returns 16:9, the 16:9 widescreen preset, diagonal 27.00 in / 68.58 cm, and centimetre equivalents of 59.77 cm by 33.62 cm. Those four numbers fit straight onto a spec sheet.

Once the panel dimensions are locked, the Diagonal Of Rectangle Calculator lets you sanity-check the diagonal against a standalone Pythagorean calculation if a vendor spec quotes a slightly different value.

Why buyers, designers and AV installers reach for a screen ratio calculator instead of working out ratios and diagonals by hand.

• • Name the panel without arithmetic: Skip the GCD reduction and let the calculator return the simplified 16:9, 16:10, 4:3 or 21:9 pair.
• • Match vendor specs in seconds: Compare a '32 inch class' label against actual width and height to sanity-check a product page.
• • Plan mounts and bezels: Use the centimetre outputs to align a VESA mount, kiosk frame or video wall seam with the panel's edge positions.
• • Quote and document with both units: Generate inch and centimetre values so a spec sheet, vendor quote and CAD drawing all agree.
• • Catch mismatched marketing numbers: Spot the difference between a 32 inch 16:9 TV and a 32 inch 21:9 cinema display at a glance.
• • Quickly check unusual orientations: Confirm whether the simplified pair flips to 9:16 in portrait before cutting a custom enclosure.

Most of these benefits come from removing arithmetic that is easy to get wrong. When the calculator names the ratio and prints the diagonal, there is no opportunity to mis-key a number or drop a factor of 100.

A 16:10 and a 16:9 monitor with the same diagonal occupy different horizontal space on a desk, and only the centimetre outputs make that difference visible at a glance.

When the panel ratio must be scaled to a different width or height, the Equivalent Ratio Calculator scales the simplified pair to any target dimension while preserving the 16:9 ratio exactly.

What changes the simplified pair, the preset match, or the diagonal size the calculator returns.

• • The calculator only handles a single rectangular panel. Curved, ultra-narrow bezel arrays, and wraparound displays need per-segment measurements.
• • The preset list covers the standards most users meet on a spec sheet. Specialty broadcast ratios such as 2:1, 2.20:1 or 2.39:1 return the exact simplified pair without a named preset.
• • Diagonal size uses the Pythagorean theorem on the two edges. Manufacturer marketing numbers sometimes round this value, so a calculated 31.99 in panel can still be labelled as 32 inch class.

These limits are why the calculator shows the decimal ratio and simplified pair next to the preset match. When the preset is wrong, the simplified pair is still the authoritative answer for naming the screen.

For most consumer and office displays, the limits do not matter. The diagonal matches the marketing label within a tenth of an inch and the preset list covers most practical panels.

According to VESA display timing standards, both the 4:3 raster in legacy monitors (1024x768 XGA) and the 16:9 raster in modern panels are governed by VESA's coordinate video timing specs, so those ratios recur in spec sheets.

When the Pythagorean diagonal needs to be confirmed against a separate right triangle calculation, the Pythagoras Triangle Calculator accepts the two catheti in any unit and returns the hypotenuse, area and perimeter.