Ideal weight calculator

What is an “ideal weight” really?

Most searches for an ideal weight calculator are really asking one of two questions: am I a healthy weight for my height? or how far am I from where I want to be? Both are reasonable questions. Neither has a single-number answer.

What exists is a healthy weight range — the band of weights at which the health risks linked to being too heavy or too light are lowest for a given height. Public-health bodies including the NHS and WHO define that band with body mass index (BMI), between 18.5 and 24.9. For a 168 cm adult, that works out to roughly 52–70 kg. Anywhere in the band is reasonable; the exact “ideal” point within it depends on things BMI can’t see.

The honest answer is that there is no single ideal weight, only ranges — and that’s good news. A range gives you breathing room. A specific number doesn’t.

How the calculator works — three formulas combined

Any ideal body weight formula you’ll see online traces back to one of three approaches. This calculator combines all three so the range reflects more than any single method.

1. The BMI-derived range (primary)

The main output is your healthy weight range calculated from BMI:

Lower bound = 18.5 × height_m²
Upper bound = 24.9 × height_m²

This is the range the NHS, the World Health Organization and most national health services use as their healthy-weight reference. It’s a population-level guideline, not a diagnosis.

2. The Devine formula (clinical reference)

Male:   50   + 2.3 × (height_inches − 60)
Female: 45.5 + 2.3 × (height_inches − 60)

The Devine formula was introduced in 1974 and is still used in clinical settings — particularly for drug dosing — where a single reference weight is needed. Pai & Paloucek’s 2000 review traces its origins and notes that it was never designed as a weight-loss goal; it’s a clinical convenience number¹.

3. The Robinson formula (refinement)

Male:   52 + 1.9 × (height_inches − 60)
Female: 49 + 1.7 × (height_inches − 60)

The Robinson formula (1983) tweaks Devine to better match contemporary height-weight tables. We average Devine and Robinson to show a single “mid-range clinical reference” number, but we don’t recommend treating it as a target — the BMI range is the framework that matters for everyday use.

Why ideal weight is a range, not a number

BMI is a useful screening tool at the population level, but it doesn’t distinguish between muscle and fat, and it doesn’t adjust for body composition or ethnicity. Three things matter enough to mention:

Muscle mass. A 75 kg recreational lifter at 168 cm can have less body fat than a 60 kg sedentary person at the same height — the BMI-based “ideal” weight treats them the same, but they’re not.

Ethnicity. The WHO’s 2004 consultation on BMI concluded that Asian populations have a meaningfully higher health risk at lower BMI values than the 25.0 overweight cut-off suggests². A BMI meta-analysis the previous decade had already shown body-fat-to-BMI relationships vary systematically across ethnic groups⁴. If you’re of South Asian, East Asian or Black heritage, the healthy range for your body may sit slightly below the 18.5–24.9 default.

Frame and bone density. Two people at the same height can genuinely have different “comfortable” weights, and the BMI band accommodates that by spanning roughly 20 kg at most adult heights — the full band is healthy, not just the midpoint.

Healthy weight by height — quick reference

The table below shows the BMI-derived healthy weight range for common adult heights. Use it as a cross-check against the calculator above; values are the same.

Metric

• 152 cm (5′0″) — 42.7–57.5 kg
• 160 cm (5′3″) — 47.4–63.7 kg
• 168 cm (5′6″) — 52.2–70.3 kg
• 175 cm (5′9″) — 56.7–76.3 kg
• 183 cm (6′0″) — 61.9–83.5 kg
• 190 cm (6′3″) — 66.8–90.1 kg

These are the same numbers for everyone at the height — “ideal weight for women” and “ideal weight for men” land in the same BMI band. Sex matters much more for body-composition targets (fat-free mass, muscle distribution) than for the healthy-weight band itself.

How the range changes with age and muscle mass

The 18.5–24.9 BMI band was developed using data from adults aged 18–65. For older adults, the evidence shifts.

Winter and colleagues’ 2014 meta-analysis of all-cause mortality in adults aged 65 and over found the lowest mortality sits at a BMI of 23.0–29.9 — meaningfully higher than the standard adult band³. Being at the low end of the standard “healthy” range (BMI 20–21) was associated with a higher mortality risk than being in the standard “overweight” range. Translation: if you’re over 65, a goal weight of “BMI 22” is worse evidence-backed than a goal of “BMI 25.”

Muscle mass shifts the picture similarly at any age. A resistance-trained body at BMI 26 can have less body fat than an untrained body at BMI 22. This is why our calorie calculator and protein calculator are often more useful day-to-day than a target weight — they work with body composition, not just what the scale says.

Using your healthy range without obsessing

The most useful way to use a range is loosely. Four rules of thumb:

• Anywhere in the range is fine. Don’t aim for the midpoint specifically — the health outcomes across the whole band are broadly equivalent.
• Check monthly, not daily. Daily weight fluctuates 1–2 kg with water, food volume, salt intake and menstrual cycle. The signal lives in weekly or monthly averages, not morning numbers.
• Prioritise body composition. If muscle goes up and fat goes down, the scale might barely move but your health markers improve. The scale is one signal; energy, strength and how your clothes fit are others.
• Know the red flags. Weighing yourself multiple times a day, feeling anxious about the number, restricting food when the scale doesn’t cooperate — those are signs to stop using the tool and speak to someone.

What to do if you’re far from your range

If your current weight is well outside the range, here’s the practical version:

A sustainable pace of loss is 0.25–0.5 kg per week (see our calorie deficit calculator for the maths). At that pace, 10 kg takes roughly 20–40 weeks. That can feel slow, but rapid loss is both harder to sustain and strips more muscle along the way. Getting into the upper half of your healthy range captures most of the health benefit — there’s no extra credit for hitting the lower end.

If you’re more than 20 kg above the upper end of your range, or if you have conditions like type 2 diabetes or high blood pressure, involve your GP early. A meal plan that fits your life is what makes sustained loss realistic — our healthy balanced dinners and the walkthrough at meal planning for women over 40 are both starting points, and the personalised quiz below builds a plan around your range in two minutes.

Not sure what to do with your range? Take the 2-minute quiz and we’ll build a plan around it — no counting, no shame, no single-number targets.