TV & Screen Size Converter
Turn a TV or monitor’s diagonal size into its width and height in centimetres and inches, find the biggest screen that fits your space, and see how far away to sit.
About this tool
Screen sizes are the diagonal of the picture in inches. For a 16:9 TV the width is about 87% of the diagonal and the height about 49%, so a 55-inch TV has a picture roughly 122 × 68 cm. The set itself is usually a centimetre or two bigger each way, plus the stand, so allow for that when measuring a space.
For viewing distance, cinema guidance (THX) suggests about 1.2 times the diagonal for an immersive picture and SMPTE about 1.6 times for everyday TV. With a 4K picture you can sit closer before the pixels become visible, which is why bigger screens suit smaller rooms better than they used to. Your settings are remembered on this device.