📋 Health Information · Editorial Team
Do UK Doctors Use Stone or Kg?
The NHS runs on kilograms: records, prescriptions, and BMI are all metric. But step into a consultation and your GP will happily talk stone and pounds. Here is how Britain's two-unit medical system works.
Medical disclaimer: This article explains how weight units are used in UK healthcare. It is general information, not medical advice. If you have concerns about your weight, speak to your GP or pharmacist.
The Two-Unit System: Kg on Paper, Stone in Person
British medicine officially speaks metric and conversationally speaks imperial. Every weight entered into an NHS electronic health record is stored in kilograms. A large study of UK primary care records covering 5 million adults found weights recorded in kg as the standard unit. Yet when the GP turns from the screen to the patient, the conversation usually switches: "You're about 12 and a half stone" lands in a way that "79 kilograms" does not for most British patients.
This is not sloppiness, it is deliberate communication. Doctors are trained to give information in terms patients understand, and for most adults in Britain, body weight is intuitively a stone-and-pounds concept. The kg figure goes in the notes; the stone figure goes into the patient's head.
Why Medicine Insists on Kilograms
The clinical case for metric is about safety, not snobbery:
- Drug dosing: many drug doses are calculated per kilogram of body weight (mg/kg). A weight in stone must be converted before any dose is calculated, and every conversion is a chance for error.
- BMI: body mass index is defined as kg/m². The NHS BMI calculator accepts stone and pounds as input, but it converts to metric before doing the maths.
- Trend tracking: working out a percentage change, for example a 10% weight loss target, is trivial in kilograms and fiddly in stone and pounds.
- Scale safety: a national review of medical weighing (the LACORS project, 2008 to 2009) found that nearly a third of hospital scales could switch between metric and imperial, and one in ten switchable scales was set to imperial at the time of testing, despite no medicine being dosed in imperial units. The report flagged this as a patient safety risk.
This is why hospitals have moved toward metric-only scales and why every clinical guideline, from anaesthesia to paediatrics, is written in kilograms.
What Actually Happens in a GP Appointment
A typical weight-related consultation flows like this. The nurse or healthcare assistant weighs you on a metric scale and the figure, say 82.4 kg, goes into your record. When the GP discusses it with you, they will usually translate: "That's about 13 stone." If you volunteer your weight in stone first, "I'm about 14 stone," the clinician converts it to kilograms for the notes without blinking. GPs do this conversion dozens of times a week; it is second nature.
Weight-management referrals work the same way. NHS weight-loss programmes set targets in whichever unit the patient prefers, but progress is logged in kg behind the scenes. If you are tracking your own loss at home, our guide to losing a stone works in the units you actually use.
Babies are the exception that proves the rule: newborns have been weighed in kilograms in the UK for decades. Birth weights are announced to families in pounds and ounces out of tradition, but the official record is metric. If anyone in British medicine were going to use stone, it would be midwives, and even they use kg.
Which Unit Should You Track Your Weight In?
Honestly, either. The best unit is the one you will actually use consistently. Stone and pounds have a psychological advantage for many British people: milestones feel meaningful ("I got under 12 stone") in a way that kilogram numbers often do not. Kilograms have a practical advantage: they make small changes visible, since 0.5 kg is a finer increment than a pound, and they match what your GP has on file.
Many people use both: stone for the headline number they tell friends, kilograms for the spreadsheet. If you need to move between them, our stone to kg chart and BMI calculator (which accepts stone, pounds, and kg) have you covered.
Frequently Asked Questions
Do UK doctors use stone or kg?
Both, in different places. NHS medical records are kept in kilograms, which is the clinical standard. But doctors and nurses routinely translate into stone and pounds when talking to patients, because that is the unit most British patients understand.
Why do NHS records use kilograms?
Kilograms are the international medical standard. Drug doses are calculated per kilogram of body weight, BMI is computed from kg and metres, and metric units avoid the conversion errors that imperial units can cause. A national review of hospital weighing found switchable imperial/metric scales to be a patient safety risk.
Will my GP understand my weight in stone?
Yes. GPs are completely fluent in stone and pounds and will usually ask for, or convert to, the unit you are comfortable with. If you say '12 stone', your GP knows exactly what you mean and will record the kilogram equivalent.
Are babies weighed in stone or kg in the UK?
Kilograms. Babies have been weighed in metric in the UK for decades. Birth weights are announced in pounds and ounces for family tradition, but the official record is metric.
Should I track my weight in stone or kg?
Use whichever unit you will stick with. Stone and pounds feel more intuitive to many British people, while kilograms make small changes easier to see. What matters for health is the trend, not the unit.