Screen Proportion Calculator

Use this calculator to determine the dimensions (width, height, diagonal) and aspect ratio of any screen. Enter at least two known values, such as the diagonal length and aspect ratio, or the screen's width and height, and the calculator will provide the missing measurements.

Diagonal (inches):

Width (inches):

Height (inches):

Aspect Ratio X (e.g., 16):

Aspect Ratio Y (e.g., 9):

.calculator-container { background-color: #f9f9f9; border: 1px solid #ddd; padding: 20px; border-radius: 8px; max-width: 600px; margin: 20px auto; font-family: Arial, sans-serif; } .calculator-container h2 { color: #333; text-align: center; margin-bottom: 20px; } .calculator-container p { color: #555; margin-bottom: 15px; line-height: 1.6; } .calc-input-group { margin-bottom: 15px; } .calc-input-group label { display: block; margin-bottom: 5px; color: #333; font-weight: bold; } .calc-input-group input[type="number"] { width: calc(100% – 22px); padding: 10px; border: 1px solid #ccc; border-radius: 4px; box-sizing: border-box; } .calculator-container button { display: block; width: 100%; padding: 12px 20px; background-color: #007bff; color: white; border: none; border-radius: 4px; font-size: 16px; cursor: pointer; transition: background-color 0.3s ease; margin-top: 20px; } .calculator-container button:hover { background-color: #0056b3; } .calculator-result { margin-top: 25px; padding: 15px; background-color: #e9f7ef; border: 1px solid #d4edda; border-radius: 4px; color: #155724; } .calculator-result h3 { color: #155724; margin-top: 0; margin-bottom: 10px; } .calculator-result p { margin-bottom: 8px; color: #155724; } .calculator-result p strong { color: #0e3c17; } .calculator-result .error { color: #721c24; background-color: #f8d7da; border-color: #f5c6cb; padding: 10px; border-radius: 4px; } // GCD function for simplifying integer aspect ratios function gcd(a, b) { a = Math.round(a); // Ensure integers for GCD b = Math.round(b); // Ensure integers for GCD while (b) { var temp = b; b = a % b; a = temp; } return a; } function calculateProportions() { var diagonalInputVal = parseFloat(document.getElementById('diagonalInput').value); var widthInputVal = parseFloat(document.getElementById('widthInput').value); var heightInputVal = parseFloat(document.getElementById('heightInput').value); var arXInputVal = parseFloat(document.getElementById('aspectRatioXInput').value); var arYInputVal = parseFloat(document.getElementById('aspectRatioYInput').value); var resultHtml = "; var finalDiagonal, finalWidth, finalHeight, finalArX, finalArY; // Helper to check if a value is a valid positive number function isValid(val) { return !isNaN(val) && val > 0; } // Determine which inputs are valid var hasDiagonal = isValid(diagonalInputVal); var hasWidth = isValid(widthInputVal); var hasHeight = isValid(heightInputVal); var hasAr = isValid(arXInputVal) && isValid(arYInputVal); // — Calculation Logic — // Case 1: Aspect Ratio (AR) is known if (hasAr) { var arRatio = arXInputVal / arYInputVal; var arHypotenuse = Math.sqrt(arXInputVal * arXInputVal + arYInputVal * arYInputVal); if (hasDiagonal) { // Diagonal + AR finalDiagonal = diagonalInputVal; finalWidth = diagonalInputVal * arXInputVal / arHypotenuse; finalHeight = diagonalInputVal * arYInputVal / arHypotenuse; } else if (hasWidth) { // Width + AR finalWidth = widthInputVal; finalHeight = widthInputVal / arRatio; finalDiagonal = Math.sqrt(finalWidth * finalWidth + finalHeight * finalHeight); } else if (hasHeight) { // Height + AR finalHeight = heightInputVal; finalWidth = heightInputVal * arRatio; finalDiagonal = Math.sqrt(finalWidth * finalWidth + finalHeight * finalHeight); } } // Case 2: Width and Height are provided (and not already calculated by AR) if (hasWidth && hasHeight && !isValid(finalDiagonal)) { finalWidth = widthInputVal; finalHeight = heightInputVal; finalDiagonal = Math.sqrt(finalWidth * finalWidth + finalHeight * finalHeight); } // Case 3: Diagonal and Width are provided (and not already calculated) if (hasDiagonal && hasWidth && !isValid(finalHeight)) { if (diagonalInputVal * diagonalInputVal < widthInputVal * widthInputVal) { resultHtml = 'Error: Diagonal cannot be shorter than width.'; } else { finalDiagonal = diagonalInputVal; finalWidth = widthInputVal; finalHeight = Math.sqrt(finalDiagonal * finalDiagonal – finalWidth * finalWidth); } } // Case 4: Diagonal and Height are provided (and not already calculated) if (hasDiagonal && hasHeight && !isValid(finalWidth)) { if (diagonalInputVal * diagonalInputVal 1000 || simplifiedArY > 1000) { // Heuristic threshold finalArX = finalWidth.toFixed(2); finalArY = finalHeight.toFixed(2); } else { finalArX = simplifiedArX; finalArY = simplifiedArY; } } else { finalArX = null; // Cannot determine AR finalArY = null; } // Display Results if (resultHtml === ") { // Only display if no error occurred if (isValid(finalDiagonal) && isValid(finalWidth) && isValid(finalHeight)) { resultHtml += '

Calculated Screen Proportions:

'; resultHtml += 'Diagonal: ' + finalDiagonal.toFixed(2) + ' inches'; resultHtml += 'Width: ' + finalWidth.toFixed(2) + ' inches'; resultHtml += 'Height: ' + finalHeight.toFixed(2) + ' inches'; if (isValid(finalArX) && isValid(finalArY)) { resultHtml += 'Aspect Ratio: ' + finalArX.toFixed(0) + ':' + finalArY.toFixed(0) + "; } else { resultHtml += 'Aspect Ratio: Not enough information or not a simple integer ratio.'; } } else { resultHtml = 'Please enter at least two valid values (e.g., Diagonal and Aspect Ratio, or Width and Height) to calculate the screen proportions.'; } } document.getElementById('result').innerHTML = resultHtml; }

Understanding Screen Proportions and Aspect Ratios

Screen proportion, often referred to as aspect ratio, describes the proportional relationship between a screen's width and its height. It's a fundamental characteristic of any display, from your smartphone to a large cinema screen, influencing how content is displayed and perceived.

What is Aspect Ratio?

An aspect ratio is expressed as two numbers separated by a colon (e.g., 16:9, 4:3). The first number represents the width, and the second represents the height. For instance, a 16:9 aspect ratio means that for every 16 units of width, there are 9 units of height.

Why are Screen Proportions Important?

Content Compatibility: Different types of media are produced with specific aspect ratios in mind. Movies might be shot in ultra-wide (e.g., 21:9), while older TV shows are often 4:3. Modern television and computer monitors typically use 16:9. Viewing content on a screen with a different aspect ratio can result in black bars (letterboxing or pillarboxing) or stretched/cropped images.
User Experience: The aspect ratio affects how much information can be displayed on a screen and how comfortable it is to view. Ultrawide monitors (21:9) are popular for productivity and immersive gaming, offering more horizontal screen real estate.
Design and Planning: When designing a home theater, choosing a projector screen, or even arranging furniture around a TV, knowing the exact dimensions derived from the diagonal and aspect ratio is crucial for proper fit and viewing distance.

Common Aspect Ratios Explained:

4:3 (Standard Definition): This was the traditional aspect ratio for older televisions and computer monitors. Many classic films and TV shows were produced in 4:3.
16:9 (Widescreen/HD): The most common aspect ratio today for HDTVs, computer monitors, and most modern video content (YouTube, Netflix, Blu-ray). It's considered the standard for high-definition viewing.
21:9 (Ultrawide/Cinemascope): Also known as 2.35:1 or 2.39:1, this ratio is popular for cinematic movies and ultrawide computer monitors. It offers a more immersive experience, especially for gaming and multitasking.
16:10: Sometimes found on laptop screens and monitors, offering a bit more vertical space than 16:9, which can be beneficial for productivity tasks.

How the Calculator Works:

The calculator uses basic trigonometry (specifically the Pythagorean theorem) to determine the missing screen dimensions. A screen's diagonal, width, and height form a right-angled triangle. If you know any two of these values, or one value and the aspect ratio, the others can be calculated.

Diagonal and Aspect Ratio: If you input the diagonal length and the aspect ratio (e.g., 27 inches, 16:9), the calculator uses the aspect ratio to find the proportional sides of the right triangle, then scales them to match the given diagonal.
Width and Height: If you provide the width and height, the diagonal is calculated using the Pythagorean theorem (a² + b² = c²), and the aspect ratio is simplified from the width and height values.
Diagonal and One Dimension (Width or Height): The calculator can use the Pythagorean theorem in reverse to find the missing dimension, then derive the aspect ratio.

Examples:

Let's look at some practical examples:

A 27-inch 16:9 Monitor:
- Input: Diagonal = 27, Aspect Ratio X = 16, Aspect Ratio Y = 9
- Output: Width ≈ 23.53 inches, Height ≈ 13.23 inches
A 55-inch 16:9 Television:
- Input: Diagonal = 55, Aspect Ratio X = 16, Aspect Ratio Y = 9
- Output: Width ≈ 47.94 inches, Height ≈ 26.96 inches
An Ultrawide Monitor with known dimensions:
- Input: Width = 34.4 inches, Height = 14.4 inches
- Output: Diagonal ≈ 37.30 inches, Aspect Ratio ≈ 21:9 (or 2.39:1)
An Old 20-inch 4:3 TV:
- Input: Diagonal = 20, Aspect Ratio X = 4, Aspect Ratio Y = 3
- Output: Width ≈ 16.00 inches, Height ≈ 12.00 inches

This calculator is a handy tool for anyone needing precise screen measurements for purchasing decisions, setup planning, or simply understanding display specifications.