Screen Size Calculator Calculate physical screen dimensions from diagonal size and aspect ratio, or diagonal from width and height.

What Is Screen Size Calculator?

The Screen Size Calculator converts between screen diagonal measurements and physical width/height dimensions. In one mode, enter a diagonal size (like "27 inches") and aspect ratio to find the actual width and height. In the other mode, enter physical width and height to find the diagonal and aspect ratio. Results are shown in both inches and centimeters, with area calculations. This is useful for comparing screen sizes, planning desk setups, or choosing the right TV size for a room.

Why Use Screen Size Calculator?

• Two modes: diagonal→dimensions or dimensions→diagonal
• Displays results in both inches and centimeters
• Shows viewable area for actual comparison
• Helpful for comparing screens with different aspect ratios

Common Use Cases

TV Shopping

Compare actual viewable area between different TV sizes and ratios.

Desk Setup

Calculate physical dimensions to plan monitor placement on a desk.

Wall Mounting

Determine TV dimensions for wall mount placement and spacing.

Projection

Calculate screen dimensions for projector setups.

Technical Guide

From diagonal and aspect ratio: Width = D × W_ratio / √(W_ratio² + H_ratio²), Height = D × H_ratio / √(W_ratio² + H_ratio²), where D is diagonal, W_ratio and H_ratio are the aspect ratio components. Area = Width × Height. From physical dimensions: Diagonal = √(Width² + Height²). Aspect ratio is found by computing GCD of width and height (after rounding to avoid floating-point issues). Conversions: 1 inch = 2.54 cm, 1 in² = 6.4516 cm².

Tips & Best Practices

• 1
  A larger diagonal does not always mean more viewable area — aspect ratio matters
• 2
  A 32" 16:9 screen has less area than a 32" 4:3 screen
• 3
  For TV viewing distance, a common rule is 1.5-2.5× the diagonal
• 4
  Ultrawide monitors (21:9) have less height than standard (16:9) at the same diagonal

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Aspect Ratio Calculator

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Frequently Asked Questions

Q How is TV size measured?

TV size is measured diagonally from corner to corner, not width or height. A 55" TV is 55 inches measured diagonally.

Q Is a 27" monitor at 16:9 the same size as 27" at 21:9?

Same diagonal, but different dimensions. 16:9 is taller (~13.2" high). 21:9 is wider but shorter (~10.4" high). The 16:9 has more total area.

Q How far should I sit from my TV?

A common rule: sit 1.5-2.5× the diagonal distance away. For a 55" TV, that is 6.8-11.5 feet. For 4K TVs, you can sit closer.

Q What size monitor should I get for my desk?

For a standard desk (24" deep): 24-27" is ideal. For deeper desks or dual monitor setups: 27-34". Measure your available space first.

Q Are quoted screen sizes accurate?

Advertised sizes include the bezel area in some cases. The viewable area may be slightly smaller than the quoted diagonal.

About This Tool

Screen Size Calculator is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.