i
Weigh in, watch the trend.
Log your weight and the app charts the line over weeks, so one heavy day doesn't read as failure.
bmi
The UK BMI calculator
BMI calculator. Check yours against the NHS bands.
Enter your height and weight for your Body Mass Index and the NHS weight category it falls in. Then see what the number leaves out, and how to track the things it misses.
Height
Weight
bmi
BMI chart by height
The BMI chart,
weight by height.
Find your height, read across for the weight range in each NHS band. The healthy column is the 18.5 to 24.9 range. Weights are in kilograms; the calculator above takes pounds too.
| Height | Underweight (kg) | Healthy weight (kg) | Overweight (kg) | Obese (kg) |
|---|---|---|---|---|
| 150cm (4'11") | under 41.6 | 41.6 to 56 | 56.3 to 67.3 | 67.5 and over |
| 154cm (5'1") | under 43.9 | 43.9 to 59.1 | 59.3 to 70.9 | 71.1 and over |
| 158cm (5'2") | under 46.2 | 46.2 to 62.2 | 62.4 to 74.6 | 74.9 and over |
| 162cm (5'4") | under 48.6 | 48.6 to 65.3 | 65.6 to 78.5 | 78.7 and over |
| 166cm (5'5") | under 51 | 51 to 68.6 | 68.9 to 82.4 | 82.7 and over |
| 170cm (5'7") | under 53.5 | 53.5 to 72 | 72.3 to 86.4 | 86.7 and over |
| 174cm (5'9") | under 56 | 56 to 75.4 | 75.7 to 90.5 | 90.8 and over |
| 178cm (5'10") | under 58.6 | 58.6 to 78.9 | 79.2 to 94.7 | 95.1 and over |
| 182cm (5'12") | under 61.3 | 61.3 to 82.5 | 82.8 to 99 | 99.4 and over |
| 186cm (6'1") | under 64 | 64 to 86.1 | 86.5 to 103.4 | 103.8 and over |
| 190cm (6'3") | under 66.8 | 66.8 to 89.9 | 90.3 to 107.9 | 108.3 and over |
| 194cm (6'4") | under 69.6 | 69.6 to 93.7 | 94.1 to 112.5 | 112.9 and over |
| 198cm (6'6") | under 72.5 | 72.5 to 97.6 | 98 to 117.2 | 117.6 and over |
Rounded to the nearest 0.1kg. The NHS uses a lower cut-off for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, so the healthy column tops out around a BMI of 23 rather than 24.9.
01
Past the number
Track what
actually moves it.
BMI is one number on one day. It shifts with what you eat and how much you move, so the single reading matters far less than the direction over weeks. NutraSafe logs your weight over time and the calories and food behind it, and on every packet you scan it reads the additives in plain English. You see the number and what is driving it.
ii
See the calories behind it.
Scan a UK barcode or search a food. Calories and macros fill in, counted against a target you set.
iii
Read the additives too.
The one thing other trackers skip: every additive on the pack, explained in plain English with the source.
iv
Vitamins and minerals.
14 vitamins and 13 minerals against the UK NRV, so a lower-calorie week still covers what your body needs.
02
The NHS bands
What each
band means.
The UK uses the World Health Organization bands, the same ones the NHS shows. Where you sit is a prompt to look closer, not a verdict on its own.
Under 18.5: underweight
Being underweight carries its own risks, from low energy to weaker bones. If you are here without trying to be, it is worth a word with your GP.
18.5 to 24.9: healthy weight
The range linked to the lowest weight-related health risk for most adults. Holding steady here is the goal for most people.
25 to 29.9: overweight
A common range and a useful early prompt. A modest calorie deficit and more daily movement shift it down over time.
30 and over: obese
The NHS links this range to higher risk of type 2 diabetes, heart disease and several other conditions. A GP can help you plan a safe, steady loss.
03
What it can't see
Where BMI
falls short.
BMI is free, instant and good enough as a first screen. It is not the whole story, and being honest about that is the point.
It can't tell muscle from fat
A rugby player and someone carrying excess fat can share a BMI. If you lift heavily, expect BMI to overstate things and lean on body-fat measures instead.
It ignores where fat sits
Fat around the middle carries more risk than fat on the hips. The NHS suggests measuring your waist alongside BMI for a fuller read.
It's not for under-18s the same way
Children and teenagers are assessed on growth centiles for their age and sex, not the adult bands.
It's a screen, not a diagnosis
Take a high or low reading to your GP. We surface the number and help you track it; we don't diagnose.
04
Frequently asked
Questions
people ask.
Answers sourced to the NHS and the World Health Organization weight categories.
How is BMI calculated?
BMI is your weight in kilograms divided by your height in metres squared. For a person who is 1.78m tall and 78kg, that is 78 divided by (1.78 x 1.78), which gives a BMI of 24.6. The calculator does it for you in centimetres or feet and inches, kilograms or pounds.
What is a healthy BMI in the UK?
The NHS uses four bands: under 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25 to 29.9 is overweight, and 30 and over is obese. For people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background the NHS sets a lower cut-off, treating 23 and above as the point to act on.
Is BMI accurate?
BMI is a quick screen, not a diagnosis. It compares your weight to your height and nothing else, so it can read high for muscular people who carry little fat, and it does not show where fat sits on your body. Read it as one signal alongside your waist measurement, how your clothes fit, and what your GP says.
Does BMI work for everyone?
The standard bands are for adults aged 18 and over. Children and teenagers are assessed on age-and-sex growth centiles instead. BMI is also less reliable during pregnancy and for very muscular people. The NHS applies a lower cut-off for several ethnic backgrounds because the health risk starts at a lower BMI.
What should I do if my BMI is in the overweight or obese range?
A higher BMI is a prompt to look at the fuller picture, not a verdict on its own. Tracking what you eat and your weight over a few weeks shows the trend and where the calories come from. The NHS suggests a steady loss of about half a kilogram a week through a modest calorie deficit. If you want a plan tailored to a health condition, that is a GP conversation.
What is the difference between BMI and body fat percentage?
BMI estimates weight relative to height and cannot tell muscle from fat. Body fat percentage measures how much of your weight is fat, usually with a DEXA scan, calipers or smart scales. Body fat percentage is more precise, but BMI is free, instant and good enough as a first screen for most people.
Aaron Keen is the founder of NutraSafe. He built this calculator on the NHS BMI bands and checks the figures against the NHS and the World Health Organization himself. About the research →
You've got the number.
Now track what moves it.
Get NutraSafe on the App Store
→
Free to download. The food log, the additive flags and 25 entries a day are free. Pro is £3.99 a month or £34.99 a year for unlimited logs, weight and vitamin tracking, AI Coach, workouts and fasting.
iPhone · iOS 17 · Cancel any timebmi