"What's my BMI — and does it actually matter?" It's one of the most-searched health questions in Ireland, and the honest answer has two parts. The number itself is simple arithmetic. What it means is where a doctor comes in — because BMI is a screening starting point, not a diagnosis, and on its own it was never designed to tell the whole story.
Quick answer (checked 15 October 2026): your BMI is your weight in kilograms divided by your height in metres squared — kg ÷ m². For adults, the standard bands are: below 18.5 underweight, 18.5–24.9 the healthy-weight range, 25 and above overweight, 30 and above obesity. And if you're wondering because of weight-loss injections: in Ireland those are licensed for adults with a BMI of 30 or above, or a BMI of 27–30 alongside at least one weight-related health condition — with a prescription only ever following a doctor's review.
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How to calculate your BMI
The metric version is the one clinicians use:
BMI = weight (kg) ÷ height (m)²
Worked example: at 95 kg and 1.75 m (5 ft 9 in), your height squared is 1.75 × 1.75 = 3.06, and 95 ÷ 3.06 = 31.0 — just into the obesity band.
If you think in stone and pounds, convert first (1 stone = 6.35 kg, 1 inch = 2.54 cm), or use the imperial version of the same formula: weight (lb) × 703 ÷ height (inches)². The same person — 15 stone (210 lb) at 5 ft 9 in (69 inches) — gives 210 × 703 ÷ 4,761 = 31.0 again.
If you'd rather not do the arithmetic at all, the two-minute Slimbr assessment calculates your BMI from your height and weight and shows where it sits against the licence criteria — and a doctor reviews the full picture, not just the number.
Healthy weight range by height
Here's the weight range that corresponds to a BMI of 18.5–24.9 for common heights, in both metric and imperial:
| Height | Healthy weight (kg) | Healthy weight (stone/lb) |
|---|---|---|
| 5 ft 0 in (1.52 m) | 43–58 kg | 6 st 11 lb – 9 st 1 lb |
| 5 ft 2 in (1.57 m) | 46–62 kg | 7 st 3 lb – 9 st 10 lb |
| 5 ft 4 in (1.63 m) | 49–66 kg | 7 st 10 lb – 10 st 5 lb |
| 5 ft 6 in (1.68 m) | 52–70 kg | 8 st 3 lb – 11 st 0 lb |
| 5 ft 8 in (1.73 m) | 55–74 kg | 8 st 10 lb – 11 st 10 lb |
| 5 ft 10 in (1.78 m) | 58–79 kg | 9 st 3 lb – 12 st 6 lb |
| 6 ft 0 in (1.83 m) | 62–83 kg | 9 st 10 lb – 13 st 2 lb |
| 6 ft 2 in (1.88 m) | 65–88 kg | 10 st 4 lb – 13 st 12 lb |
| 6 ft 4 in (1.93 m) | 69–93 kg | 10 st 12 lb – 14 st 8 lb |
Two honest caveats about this table. First, the edges are soft: a BMI of 25.1 and a BMI of 24.9 are not meaningfully different lives. Second, "healthy weight" here means "inside the standard BMI band" — it is not a statement that everything about your health is fine, or that a weight outside the band means it isn't. That's simply not what one number can tell you.
What the BMI bands mean
The banding comes from the World Health Organization's adult cut-offs — a BMI of 25 or above is classed as overweight, and 30 or above as obesity — with the finer gradations used in everyday clinical practice:
| BMI | Band | What it's used for |
|---|---|---|
| Below 18.5 | Underweight | Flags possible nutritional or health issues worth a GP chat |
| 18.5–24.9 | Healthy-weight range | The general-population reference band |
| 25–29.9 | Overweight | Where weight-related health risk starts to creep up on average |
| 30–34.9 | Obesity class I | The band where weight-loss treatment licences typically begin |
| 35–39.9 | Obesity class II | Higher average risk; stricter HSE criteria sit here too |
| 40 and above | Obesity class III | The highest average-risk band |
A word on averages: these bands were built to describe risk across large populations, and they do that job reasonably well. They were never designed to pass judgement on one individual — which is why the next section matters as much as the arithmetic.
Why doctors don't stop at the number
BMI has known blind spots, and any honest Irish clinic will tell you what they are:
- It can't tell muscle from fat. Two people at the same height and weight — a rugby player and someone carrying visceral fat around the middle — share a BMI while having very different health profiles.
- It ignores where weight is carried. Fat around the waist is the part most linked to metabolic risk, and BMI sees none of it. Waist circumference is the classic companion measure.
- It doesn't apply cleanly to everyone. It's not designed for pregnant women, athletes with high muscle mass, or frail older adults without interpretation — and for some populations, including people of South Asian background, weight-related health risk can rise at slightly lower BMIs than the standard bands suggest.
So a BMI is best read as a conversation-starter: a quick, free screening number that tells a doctor where to look next, alongside blood pressure, bloods, history and lifestyle. It's also exactly how the licence criteria use it — as a starting gate for a fuller review, never the whole decision.
See how the claim works →BMI and eligibility for weight-loss injections in Ireland
This is the question behind most "BMI calculator Ireland" searches. The European licences for the weight-loss injections prescribed in Ireland — Mounjaro and Wegovy — set two routes:
- Route 1 — BMI of 30 or above. The obesity range; the BMI threshold alone satisfies the licence.
- Route 2 — BMI of 27 to under 30, plus at least one weight-related health condition — such as high blood pressure, high cholesterol, sleep apnoea, prediabetes or type 2 diabetes.
Meeting a BMI threshold gets you to the review; it doesn't end there. A prescribing doctor checks your full history, medicines and exclusions before anything is prescribed. We break the whole eligibility picture — conditions, exclusions, the Saxenda managed-access protocol that starts around BMI 35 with prediabetes and cardiovascular risk factors, and how the review works — in who qualifies for weight-loss injections in Ireland.
Worth knowing as context: "Ozempic" is licensed in Ireland for type 2 diabetes, not weight management — the semaglutide injection licensed for weight loss is Wegovy (same drug, different licence). And everything sold as a weight-loss treatment here sits on one of three lists — licensed, unlicensed, or black-market — which we map in what's licensed in Ireland. The full menu of options, including non-injection treatments, is in our weight-loss medication guide, and what treatment itself involves is covered in the Mounjaro Ireland guide.
Curious where your own weight sits? Move the slider and see the range a supervised plan typically works across — then let a doctor look at the whole picture.
Frequently asked questions
How do I calculate my BMI in stone and pounds?
Multiply your weight in pounds by 703, then divide by your height in inches squared. (One stone is 14 lb.) Or skip the arithmetic: the healthy-weight table above covers the common heights, and the free assessment calculates it for you.
What BMI do you need for Mounjaro or Wegovy in Ireland?
The licence covers adults with a BMI of 30 or above, or 27 to under 30 with at least one weight-related condition such as high blood pressure or sleep apnoea. A doctor makes the final call after reviewing your full history — the BMI is the entry gate, not the verdict. Full detail in our eligibility explained guide.
Is BMI accurate?
It's a useful screening tool across populations, with real blind spots for individuals — it can't distinguish muscle from fat, doesn't see where weight is carried, and isn't designed for pregnancy, athletes or frail older adults. Doctors read it alongside other measures, not instead of them.
Can two people with the same BMI be completely different health-wise?
Yes — that's BMI's best-known limitation. Body composition, fat distribution, fitness, age, genetics and conditions like blood pressure all sit outside the number. That's why a BMI threshold starts a medical review rather than ending one.
Does BMI matter if I feel healthy?
A BMI in the overweight or obesity bands doesn't mean you're unwell, and a "healthy" BMI doesn't guarantee you're fine — weight-related risk is statistical, not personal destiny. If your BMI is above the healthy band, it's a reasonable prompt for a GP-level check of the things that actually predict risk: blood pressure, blood sugars and cholesterol.
Further reading
- Who qualifies for weight-loss injections in Ireland? — the full eligibility picture, conditions and exclusions
- Every weight-loss medication licensed in Ireland — injections, tablets and pharmacy options
- GLP-1 in Ireland: what's licensed and what isn't — the three lists every product sits on
- Mounjaro in Ireland: the complete guide — how the treatment works and follow-up
