UK guidance uses two BMI threshold sets: the general 25/30 overweight/obesity cutoffs, and lower NICE-recommended cutoffs of 23/27.5 for South Asian, Chinese, other Asian, Middle Eastern, Black African, and African-Caribbean adults because cardiometabolic risk rises at a lower BMI in these groups. A BMI of 23.2 therefore reads as “healthy weight” under the general brackets but “increased risk” under the adjusted ones.
Which BMI threshold table does UK guidance use?
A person 1.70 m tall weighing 67 kg has BMI 67 ÷ (1.70 × 1.70) = 67 ÷ 2.89 = 23.18, rounded to 23.2. Against the general UK/WHO adult brackets (healthy weight 18.5–24.9), 23.2 sits comfortably inside the healthy range. Against the NICE-recommended thresholds for the named ethnic groups (increased risk from 23, high risk from 27.5), the same 23.2 already falls in the increased-risk band, 1.8 points above that lower cutoff.
How do I compare a BMI against the two threshold sets?
Calculate BMI with the ordinary formula in the BMI calculator, then compare the result against the threshold table that applies: the general 25/30 brackets, or the NICE 23/27.5 brackets for the specified ethnic groups. The number itself never changes; only which threshold table is the relevant one for interpreting it changes.
What should I check before quoting a UK BMI category?
Check which threshold table a UK source is using before comparing a result against it: an NHS page discussing the general population typically uses 25/30, while NICE clinical guidance for the named higher-risk groups uses 23/27.5. A single unlabelled “BMI of 23” claim is not comparable across sources unless the threshold table is stated.
What mistakes come from mixing the two threshold tables?
Do not assume every BMI calculator or every UK source uses the same threshold table; conflating the general and ethnicity-adjusted brackets can label the same person as either healthy weight or increased risk. Do not self-apply the ethnicity-specific thresholds without the underlying rationale, which concerns cardiometabolic risk patterns, not appearance or body shape. Do not use either UK threshold table for a child; that classification method is entirely different.
What can a threshold table not decide on its own?
This guide reports which threshold tables UK clinical guidance names; it is not a personal risk assessment. Applying the correct table to an individual, and interpreting a borderline result, are matters for a clinician who can weigh family history, waist circumference, and other risk factors alongside the BMI number.
Source for the external fact
NICE guideline NG246 recommends lower BMI thresholds of 23 kg/m² (increased risk) and 27.5 kg/m² (high risk) for South Asian, Chinese, other Asian, Middle Eastern, Black African, and African-Caribbean adults, compared with 25 and 30 for the general population, in its overweight and obesity guideline.
A second worked example at a different height
A person 1.75 m tall weighing 73 kg has BMI 73 ÷ 1.75² = 73 ÷ 3.0625 = 23.84, rounded to 23.8. Against the general UK/WHO brackets, 23.8 is comfortably inside the healthy range (18.5–24.9). Against the NICE-recommended 23/27.5 thresholds for the named higher-risk groups, the same 23.8 already exceeds the 23.0 increased-risk cutoff — the same pattern as the 1.70 m example above, at a different height and weight.
Weight thresholds at a fixed height, under both scales
Converting each BMI cutoff into a weight at the 1.70 m height from the worked example shows how close together the two scales’ cutoffs actually are in kilograms.
| Threshold | Weight at 1.70 m |
|---|---|
| NICE increased risk (BMI 23) | 66.5 kg |
| General healthy-weight ceiling (BMI 25) | 72.2 kg |
| NICE high risk (BMI 27.5) | 79.5 kg |
| General obesity threshold (BMI 30) | 86.7 kg |
At this height, roughly 5.7 kg separates the NICE increased-risk cutoff from the general healthy-weight ceiling — the band where the two tables disagree about the same body weight.
Where the general 25/30 cutoffs themselves come from
The general brackets that NICE adjusts downward for named higher-risk groups are not a UK-specific invention. The World Health Organization states plainly that “overweight is a BMI greater than or equal to 25; and obesity is a BMI greater than or equal to 30” in its obesity and overweight fact sheet, without publishing an ethnicity-specific adjustment of its own. NICE’s lower cutoffs sit on top of that WHO baseline for the specific groups the guideline names, rather than replacing it for the UK population generally.
What a BMI exactly at the cutoff itself counts as
The NICE increased-risk threshold is stated as “from 23,” which is an inclusive lower bound: a BMI of exactly 23.0 already counts as increased risk under the NICE table, not as a borderline healthy-weight result. At the 1.70 m height used above, that is a weight of exactly 66.5 kg — one gram lighter, and the calculation would round to a BMI just under 23, back inside the general healthy-weight bracket, though still short of NICE’s own healthy cutoff for the named groups.
How close the 67 kg example sits to each nearby line
The worked-example weight, 67 kg at 1.70 m, sits only 0.5 kg above the NICE increased-risk cutoff (66.5 kg) but 5.2 kg below the general healthy-weight ceiling (72.2 kg). The two threshold tables are not equally far away from this particular result: under NICE’s scale it is barely over the line, while under the general scale it has considerable room before reaching the next category.
Why height-measurement precision matters more under the tighter NICE band
Because the NICE band between “healthy” and “increased risk” is narrower than the general band, a small height-measurement error is more likely to flip the category. Measuring the 67 kg example person with about 2 cm of shoe height added, at 1.72 m instead of a barefoot 1.70 m, gives 67 ÷ 1.72² = 22.65 — back under the NICE 23.0 cutoff and into the healthy-weight category, from 23.18 just over it. The same 2 cm error would not have changed this person’s general-scale category at all, since 22.65 and 23.18 both sit well inside the general 18.5–24.9 healthy band.
The same threshold gap at a shorter height
At 1.60 m, the NICE increased-risk cutoff (23) falls at 58.9 kg and the general healthy-weight ceiling (25) falls at 64.0 kg — a 5.1 kg gap, close to the 5.7 kg gap found earlier at 1.70 m. The high-risk (27.5) and obesity (30) cutoffs sit at 70.4 kg and 76.8 kg respectively. The kilogram gap between the two scales’ lower cutoffs grows slightly with height, since both cutoffs scale with height squared, but the two threshold tables stay in roughly the same relative position to each other across a typical adult height range.
Six sample weights at 1.70 m, classified both ways
| Weight | BMI | General category | NICE category |
|---|---|---|---|
| 60 kg | 20.8 | Healthy weight | Healthy weight |
| 65 kg | 22.5 | Healthy weight | Healthy weight |
| 67 kg | 23.2 | Healthy weight | Increased risk |
| 70 kg | 24.2 | Healthy weight | Increased risk |
| 75 kg | 26.0 | Overweight | Increased risk |
| 80 kg | 27.7 | Overweight | High risk |
The two tables agree at the lightest and heaviest weights shown here, but diverge in the 67–75 kg band, where the general scale still reads “healthy” or only “overweight” while NICE already reads “increased” or crosses into “high” risk.
Related calculators
Calculate the raw number in the BMI calculator, read the general screening limits in the BMI screening-limits guide, and see how the equivalent classification works for children in the child-and-teen BMI guide.