Health Calculators UK 2025 | BMI, Calories, Pregnancy & Fitness Tools

Free UK health calculators based on NHS guidelines. Calculate BMI, daily calories, body fat, pregnancy due date, BMR and TDEE. Accurate health tracking tools.

Health Calculators UK 2025

Free health and fitness calculators based on NHS guidelines. Calculate BMI, daily calories, body fat percentage, pregnancy due dates, and metabolic rates.

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BMI Calculator

Calculate your Body Mass Index using NHS-approved methodology. Get personalised weight category and health guidance.

Calculate BMI

Calorie Calculator

Calculate your daily calorie needs for weight loss, maintenance, or muscle gain based on your activity level.

Calculate Calories

BMR Calculator

Calculate your Basal Metabolic Rate - the calories your body burns at rest using Mifflin-St Jeor equation.

Calculate BMR

TDEE Calculator

Calculate Total Daily Energy Expenditure including exercise. Essential for accurate calorie planning.

Calculate TDEE

Body Fat Calculator

Estimate your body fat percentage using body measurements. More accurate than BMI for fitness tracking.

Calculate Body Fat

Pregnancy Calculator

Calculate your due date, current week, and pregnancy milestones based on last menstrual period or conception.

Calculate Due Date

Ovulation Calculator

Calculate your fertile window and ovulation date to help plan or prevent pregnancy.

Calculate Ovulation

Alcohol Units Calculator

Calculate alcohol units in your drinks. Track weekly consumption against NHS recommended limits.

Calculate Units

BMI Calculator for Children

Calculate BMI percentiles for children and teenagers using age and sex-specific NHS growth charts.

Calculate Kids BMI

BMI Calculator for Women

Calculate BMI with women-specific health guidance and body composition context based on NHS guidelines.

Calculate BMI

Macro Calculator

Calculate your daily macronutrient targets for protein, carbs and fats based on your goals and activity level.

Calculate Macros

Sleep Calculator

Calculate optimal bedtime and wake-up times based on sleep cycles. Get NHS-aligned sleep recommendations.

Calculate Sleep

kJ to Calories Calculator

Convert kilojoules to calories and vice versa. Essential for reading UK and international food labels.

Convert kJ to Calories

Maintenance Calorie Calculator

Calculate your exact maintenance calories to maintain your current weight based on activity and body metrics.

Calculate Maintenance Calories

Complete Guide to UK Health Metrics and NHS Guidelines

Understanding your health metrics is fundamental to maintaining wellbeing and making informed lifestyle decisions. In the UK, the National Health Service (NHS) provides evidence-based guidelines that help millions of people track and improve their health. Our comprehensive health calculators are designed specifically for UK residents, incorporating NHS-approved formulas and reference ranges used by healthcare professionals across the country.

Whether you're monitoring your weight through BMI calculations, planning a pregnancy, managing daily calorie intake for weight management, or tracking alcohol consumption against recommended limits, our calculators provide accurate, instant results based on the latest medical research and UK health standards.

NHS Health Guidelines: All calculators on this page use formulas and reference ranges endorsed by the National Health Service and aligned with NICE (National Institute for Health and Care Excellence) guidelines. For medical concerns or before making significant health changes, always consult your GP or healthcare professional.

Understanding Body Mass Index (BMI)

Body Mass Index remains the most widely used screening tool for weight-related health risks in the UK. Calculated by dividing your weight in kilograms by your height in metres squared (kg/m²), BMI provides a quick assessment of whether your weight falls within a healthy range for your height.

The NHS uses BMI as a primary indicator for weight management programmes, referrals to weight loss services, and eligibility for certain treatments. While BMI has limitations - it doesn't distinguish between muscle and fat mass - it remains clinically useful for population-level health assessments and individual screening.

NHS BMI Categories and Health Implications

BMI RangeCategoryHealth Risk LevelNHS Recommendations
Below 18.5UnderweightNutritional deficiency riskGP consultation for underlying causes
18.5 - 24.9Healthy WeightLowest riskMaintain through balanced diet and exercise
25 - 29.9OverweightIncreased riskLifestyle changes, NHS Better Health programme
30 - 34.9Obese Class IHigh riskGP-supported weight management
35 - 39.9Obese Class IIVery high riskSpecialist referral, structured programmes
40+Obese Class IIIExtremely high riskBariatric surgery consideration
Ethnicity-Adjusted BMI Thresholds: For people of Asian, Chinese, Middle Eastern, Black African or African-Caribbean heritage, the NHS uses lower thresholds as health risks begin at lower weights. Healthy BMI: 18.5-23, Overweight: 23-27.5, Obese: 27.5+. These adjusted thresholds reflect research showing increased risk of type 2 diabetes and cardiovascular disease at lower BMIs in these populations.

Understanding Your Metabolism: BMR and TDEE Explained

Your metabolism determines how your body converts food into energy. Understanding the components of metabolism is essential for effective weight management, whether your goal is losing, gaining, or maintaining weight.

Basal Metabolic Rate (BMR)

BMR represents the calories your body burns at complete rest to maintain vital functions:

  • Breathing and oxygen circulation
  • Blood circulation and heart function
  • Brain activity and nervous system
  • Cell production and repair
  • Temperature regulation

Typical range: 1,200-2,000 kcal/day depending on age, sex, height, and weight. BMR accounts for 60-75% of daily calorie expenditure.

Total Daily Energy Expenditure (TDEE)

TDEE includes BMR plus all additional energy expenditure:

  • TEF (10%): Thermic Effect of Food - energy used digesting
  • NEAT: Non-Exercise Activity Thermogenesis - daily movement
  • Exercise: Planned physical activity

Activity multipliers:

  • Sedentary (desk job): BMR x 1.2
  • Light activity: BMR x 1.375
  • Moderate activity: BMR x 1.55
  • Very active: BMR x 1.725
  • Extremely active: BMR x 1.9

Daily Calorie Requirements by Age and Activity

Age GroupWomen (Sedentary)Women (Active)Men (Sedentary)Men (Active)
19-252,000 kcal2,400 kcal2,400 kcal3,000 kcal
26-351,800 kcal2,200 kcal2,400 kcal3,000 kcal
36-451,800 kcal2,200 kcal2,200 kcal2,800 kcal
46-551,800 kcal2,200 kcal2,200 kcal2,800 kcal
56-651,600 kcal2,000 kcal2,200 kcal2,600 kcal
65+1,600 kcal2,000 kcal2,000 kcal2,400 kcal

Body Fat Percentage: A Better Measure of Body Composition

While BMI is useful for general screening, body fat percentage provides a more accurate picture of body composition. Two people with identical BMIs can have very different amounts of muscle versus fat, leading to different health outcomes.

ClassificationWomenMenDescription
Essential Fat10-13%2-5%Minimum for basic physical and physiological health
Athletic14-20%6-13%Typical of athletes and very fit individuals
Fitness21-24%14-17%Leaner than average, good muscle definition
Acceptable25-31%18-24%Average range, healthy for most people
Obese32%+25%+Increased health risks

UK Pregnancy Care and Due Date Calculation

Pregnancy in the UK is supported by comprehensive NHS antenatal care. Understanding pregnancy dating and milestones helps expectant parents prepare for their baby's arrival and engage effectively with healthcare services.

NHS Pregnancy Timeline

  • 8-14 weeks: Dating scan - confirms due date
  • 10-14 weeks: Combined screening test option
  • 16 weeks: Midwife appointment
  • 18-21 weeks: Anomaly scan
  • 25 weeks: Midwife (if first pregnancy)
  • 28 weeks: Midwife, blood tests, anti-D if needed
  • 31-34 weeks: Midwife appointments
  • 36-41 weeks: Weekly appointments until birth

Due Date Calculation Methods

Naegele's Rule (LMP): Add 280 days (40 weeks) to first day of last menstrual period.

Conception Date: Add 266 days (38 weeks) to known conception date.

Dating Scan: Crown-rump length measurement provides most accurate dating at 8-14 weeks.

Statistics: Only 4-5% of babies arrive on their due date. 80% arrive within 2 weeks of the estimated date. Full term is 37-42 weeks.

NHS Alcohol Unit Guidelines

The Chief Medical Officers' guideline for both men and women is that to keep health risks from alcohol to a low level, it is safest not to drink more than 14 units a week on a regular basis. Understanding units helps you track consumption accurately.

Drink TypeVolumeTypical ABVUnits
Single small spirit25ml40%1 unit
Standard wine glass175ml12%2.1 units
Large wine glass250ml12%3 units
Pint of lower-strength lager568ml3.6%2 units
Pint of higher-strength lager568ml5.2%3 units
Bottle of wine750ml12%9 units
Alcopop bottle275ml5%1.4 units
Unit Calculation Formula: Units = (Volume in ml × ABV%) ÷ 1,000. For example, a 175ml glass of 13% wine = (175 × 13) ÷ 1,000 = 2.3 units. Spread your units over 3+ days with several alcohol-free days each week for lowest health risk.

NHS Physical Activity Guidelines

Regular physical activity reduces risk of major illnesses including heart disease, stroke, type 2 diabetes, and cancer by up to 50%, and lowers risk of early death by up to 30%. The NHS recommends:

  • Adults 19-64: At least 150 minutes moderate intensity OR 75 minutes vigorous intensity activity per week, PLUS strength exercises 2+ days per week
  • Adults 65+: Same as above, PLUS activities to improve balance and flexibility at least twice weekly
  • Moderate activities: Brisk walking, cycling, dancing, water aerobics, pushing a lawn mower
  • Vigorous activities: Running, swimming, cycling fast, singles tennis, football, hiking uphill
  • Strength activities: Weight training, resistance bands, heavy gardening, yoga, carrying heavy shopping

NHS Digital Health Services

The NHS provides several free digital services to support health management:

  • NHS App: Book GP appointments, order repeat prescriptions, view medical records, access NHS 111 online
  • NHS Better Health: Free tools and support for quitting smoking, drinking less, eating better, and moving more
  • Couch to 5K: Free NHS running app to help beginners build up to running 5km
  • NHS Weight Loss Plan: 12-week diet and exercise plan with weekly structure and support

Frequently Asked Questions

What is a healthy BMI according to the NHS?
According to the NHS, a healthy BMI for adults is between 18.5 and 24.9. Below 18.5 is underweight, 25-29.9 is overweight, and 30+ is obese. For people of Asian, Chinese, Middle Eastern, Black African or African-Caribbean ethnicity, healthy BMI thresholds are lower: 18.5-23 is healthy, 23-27.5 is overweight, and 27.5+ is obese. Children's BMI is calculated using age and sex-specific percentiles.
How many calories should I eat per day to lose weight?
The NHS recommends approximately 2,000 calories per day for women and 2,500 for men to maintain weight. To lose weight safely, reduce intake by 500-600 calories daily, which typically results in 1-2 lbs (0.5-1kg) weight loss per week. Never go below 1,200 calories for women or 1,500 for men without medical supervision. Use a TDEE calculator for personalised requirements based on your activity level.
How is pregnancy due date calculated?
Pregnancy due date is calculated using Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). Alternatively, add 266 days to conception date if known. Only 4-5% of babies arrive on their exact due date. NHS dating scans at 8-14 weeks provide the most accurate dating by measuring the baby's crown-rump length.
What is the weekly alcohol limit in the UK?
NHS guidelines recommend no more than 14 units of alcohol per week for both men and women, spread over 3+ days with several alcohol-free days. One unit equals 10ml of pure alcohol - approximately half a pint of 4% beer (1 unit), a 125ml glass of 12% wine (1.5 units), or a 25ml spirit (1 unit). Regularly drinking above 14 units increases health risks.
What's the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest to maintain vital functions - typically 1,200-2,000 calories. TDEE (Total Daily Energy Expenditure) includes BMR plus all other activity including digestion, movement, and exercise. TDEE is always higher and is the correct number for calorie planning. Multiply BMR by 1.2-1.9 depending on activity level.
What is a healthy body fat percentage?
Healthy body fat varies by sex. For men: athletic 6-13%, fitness 14-17%, acceptable 18-24%, obese 25%+. For women: athletic 14-20%, fitness 21-24%, acceptable 25-31%, obese 32%+. Women naturally carry more essential fat for reproductive functions. Methods for measuring include DEXA scans (most accurate), bioelectrical impedance, skinfold calipers, or body circumference calculations.
When is the most fertile time to conceive?
The most fertile time is the 5 days before ovulation plus ovulation day itself. Ovulation typically occurs 12-14 days before your next period. For a 28-day cycle, this is around day 14. Sperm survive up to 5 days; eggs survive 12-24 hours. Having intercourse every 2-3 days throughout your cycle ensures sperm are present when ovulation occurs.
How much exercise does the NHS recommend?
NHS guidelines recommend at least 150 minutes of moderate-intensity activity (brisk walking, cycling) OR 75 minutes of vigorous activity (running, swimming) per week, plus strength exercises on 2+ days. Adults 65+ should also include balance and flexibility activities twice weekly. These minimums reduce risk of major diseases by 30-40%.

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Health Calculator

Comprehensive health calculations including BMI, BMR, calorie needs and body composition.

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Calculate daily calorie deficit needed for weight loss based on your goals.

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Calculate daily protein requirements based on weight, activity level and fitness goals.

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When to See Your GP: NHS Health Check Guidance

The NHS provides free health checks for adults aged 40-74 in England every five years. These checks assess your risk of developing heart disease, stroke, kidney disease, type 2 diabetes, and dementia. If you are over 40 and have not had an NHS Health Check in the last five years, contact your GP surgery to book one. The check typically includes blood pressure measurement, cholesterol testing, BMI recording, and a discussion about family medical history and lifestyle factors such as smoking, alcohol consumption, and physical activity levels.

Beyond routine health checks, the NHS recommends seeing your GP promptly if you experience unexplained weight loss, persistent fatigue lasting more than two weeks, lumps or swellings that do not go away, persistent pain without clear cause, or changes in bowel habits lasting more than three weeks. Early detection of conditions significantly improves treatment outcomes, and the UK has one of the most comprehensive primary care systems in the world with over 6,800 GP practices serving the population.

UK Health Statistics at a Glance

Understanding national health trends helps contextualise your own metrics. According to NHS Digital, approximately 26% of adults in England are classified as obese (BMI 30+), and a further 38% are overweight (BMI 25-29.9). The average adult in England consumes around 200-300 more calories per day than recommended. Physical inactivity costs the NHS an estimated 700 million pounds annually, and only 67% of adults meet the recommended 150 minutes of moderate activity per week. Regular use of health calculators to monitor BMI, calorie intake, and activity levels can help you stay within healthy ranges and reduce your risk of chronic disease.

Frequently Asked Additional Health Questions

How often should I get an NHS Health Check?
The NHS Health Check is offered every five years to adults aged 40 to 74 who do not already have a pre-existing condition such as heart disease, diabetes, or kidney disease. The check takes about 20-30 minutes and is completely free. It includes blood pressure, cholesterol, and blood sugar tests, plus BMI measurement and lifestyle assessment. If any risks are identified, your GP will discuss next steps including potential referrals or lifestyle programmes.
What is the NHS Eatwell Guide?
The NHS Eatwell Guide is the UK government's recommended dietary framework. It advises that roughly a third of your diet should come from fruits and vegetables, another third from starchy carbohydrates (preferring wholegrain), with smaller portions of protein (beans, pulses, fish, eggs, meat), dairy or alternatives, and minimal amounts of foods high in fat, salt, and sugar. The guide recommends 6-8 glasses of water daily and limiting added sugars to no more than 30g per day for adults.
How accurate are online BMI calculators compared to a GP assessment?
Online BMI calculators use the same formula as GP surgeries (weight in kg divided by height in metres squared), so the numerical result is equally accurate provided you input correct measurements. However, a GP assessment adds clinical context: they consider muscle mass, ethnicity-adjusted thresholds, waist circumference, family history, and overall health. For most people, an online BMI calculator provides a reliable initial screening, but borderline results or those for athletes and elderly individuals should be discussed with a healthcare professional.
Can I access NHS mental health services through my GP?
Yes, your GP is the primary gateway to NHS mental health services. They can refer you to talking therapies (CBT, counselling), prescribe medication if appropriate, or refer to specialist mental health teams. You can also self-refer to NHS Talking Therapies (formerly IAPT) in England without a GP appointment. The NHS also provides free crisis support through NHS 111 (option 2 for mental health), the Samaritans (116 123), and local crisis teams available 24/7.