How we work

We use figures from the law and the building regulations, and your own measurements for everything else. Every result shows its workings.

Our rules

Imperial units come from their definitions in the Weights and Measures Act 1985, on legislation.gov.uk: a yard is exactly 0.9144 metres, a gallon exactly 4.54609 litres, a pound exactly 0.45359237 kilograms. US units come from the US National Institute of Standards and Technology. Stair and ramp limits come from Approved Document K, the government's guidance on the building regulations in England, on GOV.UK. Each figure is recorded with its source and the date we checked it, and the site will not build if one is missing. You can see them all.

Why we ask for your product's sizes

Bricks, tiles, rolls of wallpaper, packs of flooring, tins of paint and bags of gravel all come in different sizes, and no law or official body says what size they should be. So we do not assume one. The calculators start with example numbers you can change, and say where to find the real ones: on the pack, the tin, the label or from your supplier.

Our calculators give information, not advice. They work from what you enter. Check anything structural, or anything that needs building regulations approval, with your building control body.

How we test the sums

Every conversion is tested against the exact values the definitions give: an inch is 2.54 centimetres, a foot 0.3048 metres, a mile 1.609344 kilometres. The stair and ramp checks are tested against Approved Document K's own examples, such as its note that a 4 metre ramp may be as steep as 1 in 14.

Corrections

We have not had to correct any figure yet. If you spot a mistake, email max@youellsystems.co.uk.