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Health
Health Calculators
85 free health calculators with clear, detailed guides.
All Health Calculators
Age Calculator
Calculate your exact age in years, months, days, hours, and minutes. Find the day of the week you were born and days until your next birthday.
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Age Difference Calculator
Calculate the exact age difference between two people in years, months, and days. Works for any two dates — useful for relationships, sport, and law.
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Alcohol Units Calculator
Calculate alcohol units in any drink — beer, wine, spirits, or cocktails. Check against UK weekly low-risk guidelines.
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Alcohol-Free Days & Units Tracker
Track your weekly alcohol units and alcohol-free days against NHS guidelines. Calculate your annual savings if you cut down on alcohol.
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BMI Calculator
Calculate your Body Mass Index (BMI) instantly. Enter your height and weight to find your BMI score and what it means for your health.
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BMR Calculator
Find your Basal Metabolic Rate — the number of calories your body burns at complete rest just to keep you alive.
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Blood Alcohol Content Calculator
Estimate your blood alcohol content (BAC) based on drinks consumed, weight, and time elapsed. Educational tool — never drink and drive.
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Blood Pressure Checker & Hypertension Risk Tool
Check your blood pressure reading against NHS categories. Find your hypertension stage and understand cardiovascular risk from high blood pressure.
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Blood Pressure Classification Calculator (NHS Thresholds)
Classify blood pressure readings using NHS thresholds. Identify normal, elevated, stage 1 and stage 2 hypertension with home vs clinic adjustment.
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Blood Pressure Range Checker
Check what your blood pressure reading means. See if your systolic and diastolic values are normal, elevated, or hypertensive.
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Blood Pressure Reading Classifier
Classify your blood pressure reading against NHS and ESH guidelines. Understand systolic and diastolic readings and when to seek medical advice.
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Blood Sugar (HbA1c) Conversion & Tracker
Convert between HbA1c (mmol/mol and %) and average blood glucose. Track diabetes control and pre-diabetes thresholds.
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Blood Type Compatibility — Transfusion & Donation
Check blood type compatibility for blood transfusion, plasma donation, and platelet donation. Understand ABO and Rh factor compatibility rules.
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Body Fat Calculator (US Navy Method)
Calculate body fat percentage using the US Navy tape measurement method. Neck, waist, and hip measurements with category ratings.
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Body Fat Percentage Calculator
Estimate your body fat percentage using the US Navy measurement method. Enter neck, waist, and hip measurements for an accurate body composition estimate.
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Body Surface Area Calculator
Calculate body surface area (BSA) using Mosteller, DuBois, Haycock, and Boyd formulas. Used for drug dosing, burn assessment, and renal function.
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Caffeine Half-Life & Sleep Calculator
Calculate caffeine in your system at any time based on your last drinks. Find when caffeine will be low enough for good sleep.
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Caffeine Intake Calculator
Calculate your daily caffeine intake from coffee, tea, energy drinks, and other sources. Check against safe limits and find your caffeine cut-off time.
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Calorie Deficit & Weight Loss Timeline Calculator
Calculate how long it will take to reach your target weight from a given calorie deficit. Based on the 3,500 kcal per pound rule with realistic plateau.
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Calorie Deficit Calculator
Calculate the calorie deficit needed to reach your goal weight. Find your daily target calories and see how long your weight loss will take.
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Calories From Macros Calculator
Calculate total calories from protein, carbohydrates, and fat. Verify nutrition labels and understand the calorie breakdown of any food.
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Calories in Alcohol & Weekly Intake Calculator
Calculate the exact calories in any alcoholic drink and your weekly alcohol calorie intake. Find how alcohol affects your diet and weight.
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Cardiac Output & Cardiovascular Calculator
Calculate cardiac output, stroke volume, cardiac index, and mean arterial pressure. Understand how heart rate and stroke volume affect cardiac performance.
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Child BMI Calculator (Ages 2–20)
Calculate BMI for children and teenagers aged 2–20. Uses age and sex-specific percentile charts used by the NHS and CDC — not the adult BMI scale.
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Child BMI Calculator (UK)
Calculate BMI for children aged 2–18 using UK centile charts. Results are presented as a centile rather than adult BMI categories.
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Child Growth Percentile Calculator (UK-WHO)
Calculate child height, weight, and BMI percentiles using UK-WHO growth charts. Check if growth is within healthy ranges for age and sex.
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Cholesterol Ratio Calculator
Calculate your cholesterol ratios and understand what your results mean. Total-to-HDL ratio, LDL-to-HDL ratio, and cardiovascular risk assessment.
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Daily Calorie Needs Calculator (TDEE)
Calculate your Total Daily Energy Expenditure (TDEE) and daily calorie needs. Based on Mifflin-St Jeor formula with activity multipliers.
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Daily Fibre Intake Calculator
Calculate your daily fibre intake and compare with NHS recommendations. Find food sources to reach the 30g daily target.
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Daily Hydration Needs Calculator (UK Guidelines)
Calculate daily water needs based on body weight, activity, and climate. NHS UK 6-8 glass guideline plus exercise and heat adjustments.
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Daily Protein Requirement Calculator
Calculate your optimal daily protein intake based on weight, activity level, and fitness goal. Separate from macro calculator — focused on protein.
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Daily Water Intake & Hydration Calculator
Calculate your daily water intake needs based on weight, activity level, climate, and pregnancy status. Find out how much water you should drink each day.
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Daily Water Intake Calculator
Calculate exactly how much water you should drink daily based on your weight, activity level, climate, and whether you're pregnant or breastfeeding.
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Dose Times Calculator (Every X Hours)
Work out exactly what times your doses fall when taking medicine every 4, 6, 8, or 12 hours. Simple clock-time schedule from your first dose.
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HbA1c to Average Blood Glucose Converter (UK)
Convert HbA1c (mmol/mol or %) to average blood glucose (mmol/L and mg/dL). NHS diabetes thresholds and historical units.
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Healthy Eating Plate & Portion Guide
Calculate ideal portion sizes for a balanced meal based on the NHS Eatwell Guide. Find how much of each food group to eat at every meal.
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Heart Rate Zones Calculator
Calculate your 5 training heart rate zones based on your age and resting heart rate. Optimise fat burning, aerobic fitness, and performance.
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Height & Weight Converter
Convert height between feet/inches and centimetres. Convert weight between pounds, stone, and kilograms. Essential for medical forms and international use.
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Hiking Calorie Calculator
Calculate calories burned hiking based on distance, elevation gain, weight, and pack weight. More accurate than standard exercise calculators.
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Ideal Body Weight Calculator
Calculate your ideal body weight using Devine, Hamwi, Robinson, and Miller formulas. Compare multiple methods and find your healthy weight range.
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Ideal Weight Calculator
Calculate your ideal healthy weight range based on your height and body frame. Uses multiple established medical formulas.
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Ideal Weight by Frame Size Calculator
Calculate your ideal weight range adjusted for small, medium, or large frame size. Uses the Hamwi and Robinson formulas with frame size adjustment.
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Iron Intake & Deficiency Risk Calculator
Calculate daily iron intake from foods, compare with NHS targets, and identify deficiency risk. Find food sources for haem and non-haem iron.
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Jackson-Pollock Body Fat Calculator (Skinfold)
Calculate body fat percentage using the Jackson-Pollock 3-site and 7-site skinfold equations. Caliper measurement guide and body density formula.
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Keto & Low-Carb Macro Calculator
Calculate ketogenic and low-carb macro targets — net carbs, protein, and fat — based on your TDEE, goals, and carb approach (strict keto, moderate, or.
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Lean Body Mass Calculator
Calculate your lean body mass (LBM) — the weight of everything except fat. Essential for accurate TDEE calculation and drug/supplement dosing.
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Lung Capacity & VO2 Max Estimator
Estimate your FEV1, FVC, and VO2 max from age, height, and sex. Understand what your lung function results mean.
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Lung Volumes & Spirometry Reference Calculator
Calculate predicted lung volumes (TLC, VC, FRC, FEV1) based on age, height, and sex. Understand spirometry results and what normal ranges mean.
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Macronutrient Split Calculator (Protein, Carbs, Fat)
Calculate daily protein, carb, and fat targets in grams for any calorie goal and training pattern. Based on body weight and goal.
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Macros Calculator
Calculate your ideal daily macros — protein, carbohydrates, and fat — based on your TDEE, body composition goal, and dietary preference.
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Medication Timing Calculator
Calculate when to take your next medication dose based on dosing interval. Works for 4, 6, 8, 12, and 24-hour dosing schedules.
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Menstrual Cycle & Period Calculator
Calculate your next period, fertile window, and PMS timing based on your cycle length. Track irregular cycles and understand hormonal patterns.
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Nicotine Replacement Therapy (NRT) Dose Calculator
Calculate the recommended nicotine replacement therapy dose based on daily cigarettes smoked. Find patch strength, gum, and combination NRT guidelines.
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Noise Exposure & Hearing Damage Risk Calculator
Calculate your daily noise exposure dose and cumulative hearing damage risk from headphones, concerts, and workplace noise.
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Ovulation & Fertile Window Calculator
Calculate your fertile window and predicted ovulation date based on your last period and cycle length.
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Ovulation Tracker & Conception Window Calculator
Calculate your ovulation date and fertile window based on your cycle length. Shows the 6-day fertile period and best days to conceive.
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Period & Menstrual Cycle Calculator
Calculate your next period date, fertile window, and ovulation day. Predicts the next 6 cycles based on your cycle length.
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Pregnancy Due Date Calculator
Calculate your pregnancy due date based on your last menstrual period or conception date. Includes week-by-week milestones.
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Pregnancy Due Date Calculator (LMP & Conception Methods)
Calculate your pregnancy due date from your last period, conception date, or IVF transfer date. Shows trimester dates and week-by-week milestones.
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Pregnancy Week Calculator
Find out exactly how many weeks and days pregnant you are from your last period or due date. Shows trimester, key milestones, and appointment schedule.
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Pregnancy Weight Gain Calculator
Calculate recommended weight gain during pregnancy based on pre-pregnancy BMI. Tracks healthy gain ranges by trimester aligned with NHS and IOM guidelines.
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Resting Heart Rate Calculator (Fitness & Health)
Assess your resting heart rate against age and fitness norms. Identify athlete, healthy, or elevated heart rate ranges with fitness implications.
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Resting Metabolic Rate (RMR) Calculator
Calculate your Resting Metabolic Rate — the calories your body burns at complete rest. Uses the Mifflin-St Jeor equation, the most accurate standard formula.
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Running Calorie Calculator
Calculate calories burned running based on distance, pace, weight, and terrain. More accurate than general calorie counters — accounts for running efficiency.
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Sleep Calculator
Calculate the best bedtime or wake-up time to feel refreshed. Based on 90-minute sleep cycles to avoid waking during deep sleep.
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Sleep Cycle & Wake Time Calculator
Calculate optimal sleep and wake times based on 90-minute sleep cycles. Avoid waking mid-cycle by timing sleep correctly.
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Sleep Debt Calculator
Calculate your accumulated sleep debt and find out how long it will take to recover. Based on your sleep need vs actual sleep hours.
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Sodium & Salt Intake Calculator
Calculate daily sodium and salt intake. Compare with NHS 6g salt limit and identify high-sodium foods in your diet.
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Spectacle Prescription & VA Calculator
Understand your glasses or contact lens prescription. Calculate spherical equivalent, reading add power, and what your vision numbers mean.
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Sunburn Risk & SPF Calculator
Calculate how long you can stay in the sun safely with your SPF sunscreen. Find UV exposure time for your skin type and location.
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Sunscreen SPF & Sun Exposure Calculator
Calculate how long you can stay in the sun safely based on your SPF, skin type, and UV index. Know when to reapply sunscreen.
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Swimming Calories Burned Calculator
Calculate calories burned swimming by stroke, speed, and body weight. Compare different swimming strokes and intensities.
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TDEE Calculator
Calculate your Total Daily Energy Expenditure based on activity level. Find your maintenance calories for weight loss, gain, or management.
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Target Heart Rate Zone Calculator
Calculate your target heart rate zones for fat burning, cardio, and peak training. Based on age, max heart rate, and resting heart rate (Karvonen method).
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Target Weight Loss Timeline Calculator
Calculate how long it will take to reach your target weight at a given rate of loss. See realistic timelines based on safe, sustainable weight loss rates.
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UV Index Burn Time Calculator
Estimate how long until sunburn by UV index and skin type. Time to burn with and without sunscreen, plus reapplication guidance.
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Vitamin & Mineral Supplement Dose Calculator
Calculate recommended vitamin and mineral supplement doses based on age, sex, and UK NHS/EFSA reference nutrient intakes. Identify safe upper limits.
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Vitamin D Calculator & Deficiency Risk
Estimate your vitamin D sun exposure needs based on skin type, location, and time of year. Find out if you need a supplement and what dose.
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Vitamin D Deficiency Risk Calculator (UK)
Assess your UK vitamin D deficiency risk by skin type, sun exposure, season, and supplementation. NHS guidance on 10mcg daily intake.
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Vitamin D Sun Exposure Calculator
Estimate safe sun exposure for vitamin D by skin type, UV index, and season. Balance vitamin D synthesis against burn risk.
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Waist-to-Height Ratio Calculator
Calculate your waist-to-height ratio — a better predictor of cardiovascular risk than BMI. Find your risk category and recommended waist target.
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Waist-to-Hip Ratio Calculator
Calculate your waist-to-hip ratio (WHR) and find out what it means for your cardiovascular health risk. A better health indicator than BMI alone.
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Walking Calorie & Distance Calculator
Calculate calories burned walking any distance at any speed and weight. Includes incline adjustment and comparison with running.
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Weight-Based Medication Dose Calculator
Calculate weight-based medication doses for paracetamol, ibuprofen, and other common medicines. For reference only — always follow prescriber or package.
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Yoga & Pilates Calorie Burn Calculator
Calculate calories burned doing yoga, Pilates, or meditation. Compare different yoga styles from gentle Hatha to intense hot yoga and Power Vinyasa.
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About our health calculators
Our health calculators help you understand common health metrics: BMI and body composition, calorie and macronutrient needs, heart rate zones, pregnancy and ovulation dates, blood pressure categories, hydration, and more. Each gives a clear result with an explanation of what it means.
Health figures are only useful in context, so these calculators use established medical formulas and reference ranges (WHO, NHS) and explain how to interpret the result. Health calculators carry a clear note that they provide general information, not medical diagnosis or advice.
Every tool is free and needs no account. Use them to understand your numbers, and consult a GP or qualified professional for personal medical guidance.