Calculating screen size involves using the Pythagorean theorem, which relates the lengths of the sides of a right-angled triangle. For a rectangular screen, the width and height form the two shorter sides (legs) of the triangle, and the diagonal is the longest side (hypotenuse). The formula is:
a² + b² = c²
Where:
a is the width of the screen.
b is the height of the screen.
c is the diagonal length of the screen.
This calculator helps you determine one of these three values if you know the other two.
How the Calculator Works:
This calculator uses the Pythagorean theorem to find the missing screen dimension.
If you enter Width (pixels) and Height (pixels): The calculator will output the diagonal measurement in inches. The conversion factor used is approximately 1 inch = 96 pixels (this is a common assumption for display resolutions, though actual pixel density can vary). The formula applied is: Diagonal (inches) = sqrt(Width² + Height²) / 96.
If you enter Diagonal (inches) and Width (pixels): The calculator will determine the required Height (pixels). The formula used is: Height (pixels) = sqrt(Diagonal² * 96² - Width²).
If you enter Diagonal (inches) and Height (pixels): The calculator will determine the required Width (pixels). The formula used is: Width (pixels) = sqrt(Diagonal² * 96² - Height²).
It's important to note that screen sizes are typically measured diagonally in inches. Pixel dimensions (width and height) define the resolution, while the diagonal measurement gives a physical size indication. The conversion between pixels and inches depends on the screen's DPI (dots per inch) or PPI (pixels per inch), which isn't always standard. For general purposes, a conversion factor of 96 PPI is often used.
Use Cases:
Choosing a Monitor: Help decide if a monitor's physical size fits your desk space or viewing needs.
Designing Interfaces: Understand how different resolutions will appear on various screen sizes.
Setting Resolutions: Determine appropriate pixel dimensions for a specific diagonal screen size.
Comparing Displays: Relate pixel resolution to a common physical measurement (inches).
function calculateScreenSize() {
var widthPx = parseFloat(document.getElementById("widthPx").value);
var heightPx = parseFloat(document.getElementById("heightPx").value);
var diagonalInches = parseFloat(document.getElementById("diagonalInches").value);
var resultDiv = document.getElementById("result");
var resultHtml = "";
var pixelsPerInch = 96; // Standard assumption for screen calculations
// Case 1: Calculate Diagonal from Width and Height (pixels)
if (!isNaN(widthPx) && !isNaN(heightPx) && widthPx > 0 && heightPx > 0 && isNaN(diagonalInches)) {
var diagonalPx = Math.sqrt(Math.pow(widthPx, 2) + Math.pow(heightPx, 2));
var calculatedDiagonalInches = diagonalPx / pixelsPerInch;
resultHtml = "Calculated Diagonal: " + calculatedDiagonalInches.toFixed(2) + " inches";
document.getElementById("diagonalInches").value = calculatedDiagonalInches.toFixed(2); // Pre-fill for potential further calculations
}
// Case 2: Calculate Height from Diagonal (inches) and Width (pixels)
else if (!isNaN(diagonalInches) && !isNaN(widthPx) && diagonalInches > 0 && widthPx > 0 && isNaN(heightPx)) {
var diagonalPxSquared = Math.pow(diagonalInches * pixelsPerInch, 2);
var widthPxSquared = Math.pow(widthPx, 2);
if (diagonalPxSquared >= widthPxSquared) {
var calculatedHeightPx = Math.sqrt(diagonalPxSquared – widthPxSquared);
resultHtml = "Required Height: " + calculatedHeightPx.toFixed(0) + " pixels";
document.getElementById("heightPx").value = calculatedHeightPx.toFixed(0); // Pre-fill
} else {
resultHtml = "Error: Width is too large for the given diagonal.";
}
}
// Case 3: Calculate Width from Diagonal (inches) and Height (pixels)
else if (!isNaN(diagonalInches) && !isNaN(heightPx) && diagonalInches > 0 && heightPx > 0 && isNaN(widthPx)) {
var diagonalPxSquared = Math.pow(diagonalInches * pixelsPerInch, 2);
var heightPxSquared = Math.pow(heightPx, 2);
if (diagonalPxSquared >= heightPxSquared) {
var calculatedWidthPx = Math.sqrt(diagonalPxSquared – heightPxSquared);
resultHtml = "Required Width: " + calculatedWidthPx.toFixed(0) + " pixels";
document.getElementById("widthPx").value = calculatedWidthPx.toFixed(0); // Pre-fill
} else {
resultHtml = "Error: Height is too large for the given diagonal.";
}
}
// Case 4: Multiple inputs provided, recalculate based on most specific combination
else if (!isNaN(widthPx) && !isNaN(heightPx) && !isNaN(diagonalInches) && widthPx > 0 && heightPx > 0 && diagonalInches > 0) {
// Prioritize recalculating diagonal based on width and height
var diagonalPx = Math.sqrt(Math.pow(widthPx, 2) + Math.pow(heightPx, 2));
var calculatedDiagonalInches = diagonalPx / pixelsPerInch;
resultHtml = "Recalculated Diagonal: " + calculatedDiagonalInches.toFixed(2) + " inches";
resultHtml += "(Note: Provided diagonal was " + diagonalInches + " inches)";
document.getElementById("diagonalInches").value = calculatedDiagonalInches.toFixed(2); // Update with calculated value
}
// Edge case: Not enough valid information
else {
resultHtml = "Please enter at least two valid values.";
}
resultDiv.innerHTML = resultHtml;
}