What size TV do I need?

Screen size follows from viewing angle: how far back you sit decides how large the picture should be. The result is a range in inches, and the TVs registered for sale in the UK at that size.

Where to find the numbers

Measure from the screen wall to where you actually sit, in metres. Resolution matters because a 4K picture holds up closer than 1080p, so it supports a larger screen at the same distance.

What the figure is based on

The range runs between a 30° viewing angle, the SMPTE reference, and 40°, the THX recommendation, which is workable at 4K but not at 1080p. Diagonal = 2 × distance × tan(angle ÷ 2) ÷ 0.8716, the 16:9 width-to-diagonal ratio. It is a viewing-comfort convention, not a regulated figure.

What changes the cost

• Resolution: 4K holds up at a wider viewing angle than 1080p, so it supports a larger screen at the same distance.
• Content: film and sport suit the wider angle; a lot of standard-definition broadcast does not.
• Mounting height and eye level change the comfortable angle as much as distance does.
• Room light and reflections affect the experience more than the last few inches of diagonal.
• Larger screens use more electricity: the register shows the difference between models at the same size.

Compare TVs by energy use and running cost to see every model behind this figure.

Once you know the size, see what a TV of that size costs to run.

For a specific model or any other appliance, use the electricity cost calculator.