Trackraz
Guide

TV and monitor screen sizes, measured properly

A screen advertised as 55 inches is not 55 inches wide. That number is the diagonal, and the width you actually need to fit into a wall unit is closer to 48 inches. This guide explains what the figure measures, gives the real width and height for every common size, and shows the two checks worth doing before you buy.

Open a converterSkip to questions

What the inch figure actually measures

Screen size is quoted as the distance from one corner of the visible panel to the opposite corner. It ignores the bezel, the stand and the electronics behind the glass. That single number stayed useful for decades because most televisions were 4:3, so one figure described the shape well enough.

Widescreen changed that. At the 16:9 ratio used by almost every television and monitor today, the width is about 87 per cent of the diagonal and the height about 49 per cent. So a 55-inch television is roughly 121.8 cm wide and 68.5 cm tall, with the diagonal itself measuring 139.7 cm.

Ultrawide monitors stretch the gap further. A 34-inch 21:9 panel is 79.8 cm wide and only 33.6 cm tall, which is why it can look enormous on a desk while having less display area than a 32-inch 16:9 screen. Whenever you compare two screens with different ratios, compare width and height rather than diagonals.

Key facts

Diagonal, not width

The advertised size measures corner to corner, so the usable width is always noticeably smaller.

Width shortcut

For a 16:9 screen, multiply the inch figure by 2.21 to get the width in centimetres.

Height shortcut

Multiply the inch figure by 1.24 for the height in centimetres, again at 16:9.

Bezels add up

Allow one to three centimetres on each side for the frame, plus clearance for cables at the back.

Ratios are not comparable

A 34-inch ultrawide has less screen area than a 32-inch 16:9 panel despite the bigger number.

Stands need width

Feet on modern televisions often sit near the outer edges, so a narrow bench may not work at all.

How to get it right

1

Measure the opening

Record the width, height and depth of the space, including anything that limits the door of a cabinet.

2

Convert the diagonal

Multiply the screen size in inches by 2.54 to get the diagonal in centimetres.

3

Work out real width

Multiply the inch figure by 2.21 for width and 1.24 for height, then add two centimetres for the bezel.

4

Check the route in

Measure doorways, stair turns and lift depth — a boxed 75-inch television is wider than most internal doors.

Questions people ask

About 121.8 cm wide and 68.5 cm tall for the panel itself, with a 139.7 cm diagonal. Add roughly two to four centimetres in total for the bezel, depending on the model.

Keep reading

Height: feet, inches and cm

How to convert height between feet, inches and centimetres without the classic 5.10 mistake, plus a chart of common adult heights.

Weight: kg, pounds and stone

Convert body weight between kilograms, pounds and stone accurately — including why the 2.2 shortcut fails at higher weights.

Airline luggage limits

Cabin and checked baggage limits in both centimetres and inches, how airlines measure them, and where travellers get caught out.

Check your screen size in centimetres

Every common diagonal has its own page with the exact width, height and millimetre figures.

Open the converters