About this tool
Why use this tool
Britain still uses stones and pounds for body weight ("11 stone 4"), ounces for baby weight in newspapers, and pounds for greengrocers — while cooking, science and fitness apps mostly use grams and kilograms. Converting between all four matters for reading international recipes, following GP records (NHS charts in kg), tracking gym progress on metric-only equipment, and understanding US import instructions.
How it works
1 pound (lb) = 0.45359237 kg (1959 International Yard and Pound Agreement, adopted by UK statute). 1 stone = 14 lb = 6.35029 kg. 1 ounce (oz) = 28.3495 g. 1 kg = 2.20462 lb = 0.1574 stone. The imperial system remains lawful for retail alongside metric under the Weights and Measures Act 1985. Troy ounces (for gold and silver) = 31.1035 g — different from culinary ounces.
Real example
A person at 11 stone 4 (11st 4lb) weighs 71.7 kg. A newborn at 7 lb 8 oz = 3.40 kg. A UK recipe asking for 8 oz of butter needs 227 g. The average adult male in the UK weighs 13 st 3 lb (83.9 kg) per ONS Health Survey; the average female 11 st 2 lb (70.6 kg).
Practical tips
Kitchen shortcut: 1 lb ≈ 450 g; 1 oz ≈ 28 g; 4 oz ≈ 115 g (a standard butter block). GPs and NHS charts record in kg, but many patients still think in stones — ask your surgery for both. Gym plates in the UK are usually metric (20, 15, 10, 5, 2.5, 1.25 kg). Postal weight (Royal Mail): parcels priced by grams up to 2 kg, then kg brackets. For weightlifting competitions, British Weight Lifting follows IWF metric kilos. Newborn weight is legally recorded in grams (birth certificate) but announced in lb/oz in family circles.
Disclaimer
Conversions follow NPL/UKAS-recognised ratios. For precious metals use troy ounces. Retail traders must display metric primary units under the Weights and Measures (Metric System) Regulations, with imperial as supplementary. This tool is for general reference only, not for trade-approved weighing.