# Screen Size Calculator

URL: https://speedycalculator.com/calculators/everyday-life/screen-size/
Last updated: 2026-10-25

> The screen size calculator finds the width, height and area of a TV, monitor or phone screen from its diagonal size and aspect ratio, such as 16:9 or 21:9.

## Inputs

- Diagonal (in, cm)
- Aspect ratio width
- Aspect ratio height

## Results

- Width
- Height
- Screen area

## Formula

```
Width = diagonal × w ÷ √(w² + h²)
Height = diagonal × h ÷ √(w² + h²)
```

## Explanation

Two screens with the same diagonal can have very different areas if their aspect ratios differ.

### How to use the Screen Size Calculator

- **Diagonal**
- **Aspect ratio width**
- **Aspect ratio height**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

The diagonal is the hypotenuse of a right triangle with the aspect ratio’s proportions.

### Tips

- Use the figures printed on your product or its manual when you have them.
- Round quantities up so you are never short.
- Measure twice before you buy anything cut to size.
- Everything runs in your browser – try different values to compare options.

### Common mistakes to avoid

- Mixing units (inches and centimetres, mAh and Ah).
- Ignoring efficiency losses and safety margins.
- Treating rules of thumb as exact.

### Inputs explained

FieldWhat to enterDiagonalUnits: in, cmAspect ratio widthA numberAspect ratio heightA number

### What each result means

- **Width** = [Diagonal]×[Aspect ratio width]÷sqrt([Aspect ratio width]^2 + [Aspect ratio height]^2)
- **Height** = [Diagonal]×[Aspect ratio height]÷sqrt([Aspect ratio width]^2 + [Aspect ratio height]^2)
- **Screen area** = [Width]×[Height]

### Example values

How the main result changes when **Diagonal** changes and everything else stays at the example values above:

Diagonal (in)Width (in)27.523.9741.2535.955547.9468.7559.9282.571.911095.87

## Worked example

Inputs — Diagonal: 55 in; Aspect ratio width: 16; Aspect ratio height: 9.

Results — **Width = 47.94 in**; Height = 26.96 in; Screen area = 1,292.6 in².

## FAQ

**How big is a 55-inch TV?**
About 47.9 × 27 inches (121.8 × 68.5 cm) for 16:9.

**Does the bezel count?**
No, the diagonal measures only the visible screen.

**What formula does the Screen Size Calculator use?**
Width = diagonal × w ÷ √(w² + h²).