UK adult health checker
NHS-format BMI calculator
Check your adult BMI in kilograms or stone and pounds, switch to the lower thresholds used for several ethnic backgrounds, and see the NHS general calorie guide for weight loss. No sign-up; measurements stay on this device.
The NHS publishes lower overweight and obesity cut-offs because type 2 diabetes and cardiovascular risk can rise at a lower BMI in these groups. This choice changes the category table, not the BMI formula.
This optional choice only selects between the two general NHS Better Health figures. It is not used in the BMI calculation and it does not estimate your personal energy needs.
Your BMI sits in the published healthy range for the cut-offs you selected. BMI is only a screening measure, so waist size, blood pressure, blood tests and how your weight is changing still matter.
Save this result — come back and see how it moves.
Free — no card, 30 seconds. Your result comes with you.
The coach receives the measurement, category and selected guide — never the text you have not entered here.
The exact boundary table used above
A boundary belongs to the row that starts with that number. BMI 25.0 is overweight on the standard table; BMI 23.0 is overweight on the lower-risk table.
| Category | Standard adult cut-offs | Lower-risk cut-offs | What changes |
|---|---|---|---|
| Underweight | Below 18.5 | Below 18.5 | No change |
| Healthy weight | 18.5 to 24.9 | 18.5 to 22.9 | Upper edge is 2 BMI points lower |
| Overweight | 25.0 to 29.9 | 23.0 to 27.4 | Starts at 23 instead of 25 |
| Obese | 30.0 to 39.9 | 27.5 and above | Starts at 27.5 instead of 30 |
| Severely obese wording | 40.0 and above | 40.0 and above | A separate prompt for fuller support |
Screening aid only. For adults aged 18 and over; not for pregnancy. Children and teenagers need age-and-sex growth charts rather than the adult table.
What this NHS-format result means
BMI is weight in kilograms divided by height in metres squared. A person who is 1.70 m tall and weighs 70 kg has a BMI of 70 ÷ (1.70 × 1.70), which is 24.2. Stone and pounds produce the same result: the calculator converts them to kilograms first, and feet and inches to metres, before applying that one formula.
The decimal matters at a boundary. The standard adult table calls 24.9 healthy and 25.0 overweight. It calls 29.9 overweight and 30.0 obese. This page compares the unrounded BMI with the boundary and rounds only the number shown on screen, so a hidden decimal cannot put the result in the wrong row.
Why there are two adult tables
The BMI formula does not change with ethnicity. The interpretation does. The NHS advises adults from Asian, Black African, African-Caribbean and Middle Eastern family backgrounds that the chance of type 2 diabetes and cardiovascular disease can rise at a lower BMI. On that table, overweight begins at 23 rather than 25, and obesity begins at 27.5 rather than 30.
“Asian” is broad. The NHS wording includes South Asian backgrounds — for example Indian, Pakistani, Bangladeshi and Sri Lankan — and also Chinese and other Asian backgrounds. “Black” in this guidance refers specifically to Black African and African-Caribbean family backgrounds. Choose the lower table if that description fits your family background; it is a risk screen, not an identity test.
Selecting the lower table does not say that a condition is present. It moves the point at which a conversation about waist, blood pressure, glucose and cholesterol becomes useful. Those measurements can show a risk that BMI misses, or reassure when a BMI category looks worse than the rest of the picture.
The calorie figure is a guide, not a calculation from your BMI
NHS weight-loss guidance commonly frames a moderate reduction as about 600 kcal a day below the average intake used in its public advice. That produces the familiar population guides of around 1,400 kcal a day for most women and 1,900 kcal for most men. This page shows those figures exactly as general guides; it does not reverse-engineer a supposedly personal target from BMI.
Personal energy use depends on age, height, weight, body composition, work, steps, training and ordinary movement. Two people with the same BMI can differ by hundreds of calories a day. A useful personal estimate therefore needs more inputs and still has to be checked against several weeks of real weight change. The population guide is a starting point for meal planning, not a promise about the speed of weight loss.
Do not use a generic calorie figure during pregnancy, while breastfeeding, under age 18, during recovery from an eating disorder, or when a clinician has given you a different plan. If the suggested figure is far below what you currently eat, make a smaller change first or ask a GP or registered dietitian for individual advice.
Reading the healthy-weight range
The weight range is not a target to hit at either edge. It is the set of weights that would place this height between BMI 18.5 and the top of the selected healthy band: 24.9 on the standard table or 22.9 on the lower-risk table. A change in table can therefore change the upper number even though your height and weight stay exactly the same.
Treat it as map scale, not a deadline. Weight varies with fluid, glycogen, food in the digestive system and the time of day. If you are monitoring a change, weigh under similar conditions and follow the trend across weeks. One morning can be noisy; the direction over time is the useful signal.
When BMI is less informative
BMI cannot separate muscle, fat, bone and fluid. Someone with a large amount of muscle may fall in an overweight category with a relatively small waist. Someone else can have a BMI in the healthy range but carry more fat around the organs. Waist-to- height ratio adds information because it asks where the size is, not only how much mass is on the scale.
Pregnancy changes weight for reasons the adult BMI table was not built to interpret. Children and teenagers are still growing, so their result has to be compared with age-and-sex growth charts. Frailty and unplanned weight loss in older adults can also matter more than the category itself. In all three situations, the simple adult band is the wrong decision tool.
Medicines, swelling, recent illness and dehydration can move weight without representing a change in body fat. If a number changed quickly or does not fit how you feel, repeat the measurement and discuss the pattern rather than forcing an explanation from one BMI result.
Measuring accurately in metric or imperial
Measure height without shoes, heels against a wall, looking straight ahead. Weigh on a firm, level floor in light clothing. In imperial mode, enter the whole stone in the first weight field and the remaining pounds in the second: 12 st 6 lb is entered as 12 and 6, not 12.6 stone. Twelve point six stone means 12 stone plus 8.4 pounds, which is a different weight.
The converter accepts decimal inches and decimal pounds, so a tape reading of 5 ft 7.5 in does not need to be rounded first. Decimal commas are accepted as well. Switching units converts the current values rather than resetting them, which makes it possible to check a clinic measurement against a home scale.
Source and scope
The category boundaries and the lower ethnicity thresholds on this page follow the adult BMI guidance published on the NHS website. The calorie figures follow the NHS Better Health public weight-loss guide: around 1,400 kcal for most women and 1,900 kcal for most men. The calculator does not use NHS logos, colours or page assets and does not imply an official relationship.
Public guidance changes. If a clinician or a current NHS page gives a different instruction for your circumstances, use that instruction. This calculator's useful job is narrower: apply the published adult boundaries consistently, show exactly which table was used, and keep a general calorie guide visibly separate from a personal prescription.