Health calculators based on UK and NHS guidelines: Body Mass Index (BMI) using the NHS classifications, daily calorie requirements using the Mifflin-St Jeor equation, ideal body weight estimates, pregnancy due dates, and alcohol units following the UK Chief Medical Officers' guidelines of no more than 14 units per week.
Last verified: April 2025 against HMRC, Ofgem and gov.uk sources for the 2025/26 tax year.
Every tool below is free, requires no sign-up and uses 2025/26 UK rates.
5 health & fitness calculators covering bmi, calories, ideal weight, due date.
Not sure which tool to start with? Here's a quick guide to the most-used calculators in this category — pick the one that matches your situation.
Calculate your Body Mass Index (BMI) using the NHS BMI classification.
Calculate your daily calorie needs based on age, sex, height, weight and activity level.
Find your healthy weight range based on height using multiple formulas.
| Calculator | Best for | Time to use |
|---|---|---|
| BMI Calculator | Calculate your Body Mass Index (BMI) using the NHS BMI classification. | Under 1 min |
| Calorie Calculator | Calculate your daily calorie needs based on age, sex, height, weight and activity level. | Under 1 min |
| Ideal Weight Calculator | Find your healthy weight range based on height using multiple formulas. | Under 1 min |
| Pregnancy Due Date Calculator | Calculate your estimated due date based on your last menstrual period or conception date. | Under 1 min |
| Alcohol Units Calculator | Count alcohol units and calories in any drink based on NHS unit guidelines. | Under 1 min |
Use ethnicity-adjusted BMI thresholds
NICE recommends lower thresholds for South Asian, Black, Chinese ethnicities: overweight from 23 (not 25), obese from 27.5 (not 30). Our BMI calculator notes this.
Calculate BMR before calorie target
BMR = at-rest calorie burn. Multiply by activity factor (1.2-1.9) for total daily energy expenditure. NHS general guidelines are 2000/2500 kcal for adult women/men.
Count alcohol units, not drinks
1 UK unit = 8g pure alcohol. A pint of 5% beer = ~2.8 units. CMO low-risk guideline is 14 units/week spread over 3+ days with several drink-free days.
Use ultrasound for due date if possible
NHS ultrasound dating after 7 weeks is more accurate than Naegele's rule (LMP + 280 days). Talk to your midwife or GP.
These are guidance only
All health calculators are for general orientation. Consult a GP or qualified healthcare professional for medical decisions.
Disclaimer: All calculators on this page provide estimates for guidance only and do not constitute financial, tax or legal advice. Tax rules can change at any time — always consult a qualified professional or check gov.uk before making financial decisions.