Kalkulo

Ideal weight calculator

Get a reference healthy weight range in stones and pounds from the Lorentz formula, to cross-check against your NHS BMI category.

Result
144 – 159.1 lbs
Ideal range (Lorentz)

About this tool

Why use this tool

The ideal weight calculator gives a reference range based on height and sex. It is used alongside BMI by GPs, NHS dietitians and clinicians (including for drug dosing based on ideal body weight in anaesthesia and critical care) as a practical goal-setting tool.

How the calculation works

The Lorentz formula: ideal weight(kg) = height(cm) − 100 − (height − 150) ÷ K, with K = 4 for men, K = 2.5 for women. A ±5 % range covers frame variation. The result is displayed in stones and pounds (1 stone = 6.35 kg) as commonly used in the UK.

Real example

A man 6'0" (183 cm): ideal = 183 − 100 − (183 − 150) ÷ 4 = 74.75 kg ≈ 11 st 11 lb. Range: 11 st 3 lb to 12 st 6 lb. A woman 5'6" (168 cm): ideal = 168 − 100 − (168 − 150) ÷ 2.5 = 60.8 kg ≈ 9 st 8 lb. Range: 9 st 2 lb to 10 st 1 lb.

Practical tips

Ideal weight is only a guide. Combine it with BMI (NHS healthy range 18.5–24.9, or 18.5–22.9 for South Asian, Chinese, Black African and African-Caribbean adults per NICE), waist circumference and body fat percentage. Follow the NHS Eatwell Guide and Chief Medical Officers' guidance of 150 min/week moderate activity. Ask your GP for a free NHS Health Check or a referral to a HCPC-registered dietitian.

Disclaimer

This calculation is indicative and does not replace medical advice. It is not suitable for under-18s (use NHS growth charts), pregnant women, older adults or trained athletes. Speak to your GP before setting weight goals, and contact Beat (beateatingdisorders.org.uk) if you or someone you know is struggling with an eating disorder.

Frequently asked questions

How is my result displayed on the UK version of this calculator?⌄
The UK version converts the Lorentz formula's metric result into stones and pounds, since that remains the most familiar way to discuss body weight in the UK. You can still switch to kilograms if you prefer, and the underlying calculation is identical either way.
Does the NHS use a formula like this one?⌄
The NHS relies mainly on BMI and waist circumference for population health guidance rather than a single ideal-weight figure. Height-based reference-weight formulas similar to Lorentz are used clinically in some settings, such as calculating ideal body weight for drug dosing in anaesthesia and critical care, but they are not the NHS's general public-facing weight tool.
Do lower BMI thresholds for South Asian and Black adults affect the ideal weight range shown here?⌄
This calculator uses the standard Lorentz formula and does not adjust for ethnicity. NICE guidance does lower the overweight and obesity BMI thresholds to 23 and 27.5 for people of South Asian, Chinese, Black African and African-Caribbean background because of their higher cardiometabolic risk at a given BMI — worth bearing in mind alongside this tool's result.
What if I have a naturally larger frame?⌄
The calculator already builds in a range of about plus or minus 5% around the central figure to account for differences in bone structure and frame size, rather than presenting a single fixed number. If you have a notably large or small frame, treat the wider end of that range as your more realistic reference point.
Where can I get a proper body composition assessment in the UK?⌄
Ask your GP about a free NHS Health Check, available every five years between ages 40 and 74, which reviews weight-related risk alongside blood pressure and cholesterol. For a detailed body-fat breakdown, private DEXA scans or a HCPC-registered dietitian referral through your GP are the more precise routes.

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