Health & Fitness Calculators
BMI, body fat, hydration and pregnancy dates — quick estimates, nothing stored on any server
BMI Calculator
Calculate your body mass index in metric or imperial units and see which range you fall into, plus your healthy weight window.
Body Fat Calculator
Estimate your body fat percentage from your BMI, age and sex using the Deurenberg formula. Free, nothing is stored.
Water Intake Calculator
Find out how much water to drink each day based on your weight and how much you exercise. Free, no signup.
Pregnancy Due Date Calculator
Estimate your due date from your last period, adjusted for your cycle length, and see your current week and trimester.
How Many Weeks Pregnant Am I
See exactly how many weeks and days pregnant you are today, which trimester you are in and how long is left. Free.
BMR Calculator
Estimate your Basal Metabolic Rate using the Mifflin-St Jeor formula. Find the calories your body burns at complete rest, useful for any diet plan.
TDEE Calculator
Turn your BMR into Total Daily Energy Expenditure based on how active you really are. Pick the closest match, not the one you wish you had.
Ideal Weight Calculator
Estimate the ideal body weight range using the Devine formula, Robinson and Miller variants. All quick estimates, not goals.
Waist to Hip Ratio Calculator
Measure waist and hip to get your waist-to-hip ratio and the cardiovascular risk band that the WHO uses.
Waist to Height Ratio Calculator
The rule of thumb used by NHS: keep your waist less than half your height. Anything past that is a flag for higher cardiometabolic risk.
Lean Body Mass Calculator
Estimate your lean body mass using the Boer formula, which is more accurate than BMI for athletes and people carrying extra muscle.
Daily Protein Calculator
How many grams of protein a day for your weight and goal. Sedentary adults need less than athletes trying to keep or build muscle.
Calorie Burn Calculator
Estimate how many calories common activities burn for your body weight. MET-based approximation that gets the order of magnitude right.
Steps to Calories Calculator
Convert your daily step count into estimated calories burned, based on stride length and weight. Useful for closing Apple Watch fitness rings.
Macro Calculator
Split your daily calories into protein, carb and fat grams by goal: balanced, low-carb, high-protein, keto or endurance.
Max Heart Rate Calculator
Estimate maximum heart rate with the 220 − age formula (and the more accurate Tanaka version) so you can set training zones.
Heart Rate Zones Calculator
Five training zones — recovery, endurance, tempo, threshold and max — based on your max heart rate.
Target Heart Rate Calculator
Get the heart rate range that matches your chosen workout intensity. Plug it into your watch alert for consistent effort.
One Rep Max Calculator
Turn a set of 5-10 reps into your estimated 1RM using Epley and Brzycki formulas. Plan your percentages without hitting failure.
Ovulation Calculator
Estimate when you are most likely to ovulate based on your cycle length and last period, including the most fertile window.
Conception Date Calculator
Back-calculate when conception most likely happened from your due date or last period, useful for tracking ultrasound dating.
Trimester Calculator
See exactly which trimester you are in today, the dates the trimesters start and end, and when full term kicks in.
Sleep Cycle Calculator
90-minute sleep cycles drive when you wake up feeling alert. Find the wake-up times that land between cycles.
Calorie Deficit Calculator
Calculate how many calories you should eat to hit a chosen loss rate, including the floor where going lower risks muscle loss.
Weight Loss Calculator
How long to reach your goal at your chosen daily deficit. Honors the 7700-kcal-per-kg rule of thumb and gives a date.
Blood Alcohol Calculator
Estimate your current BAC using the Widmark formula. Educational only — never rely on this to decide if you can drive.
Pregnancy Weight Gain Calculator
See the IOM-recommended total weight gain range based on your pre-pregnancy BMI and how far along you are.
Fat Mass Calculator
From total weight and body fat percentage, get total fat mass and lean mass split into kilograms.
Skeletal Muscle Mass Calculator
Estimate skeletal muscle mass from lean body mass. Skeletal muscle is roughly half of LBM in untrained adults.
ABSI Calculator (Body Shape Risk)
A Body Shape Index — a mortality-prediction score that weights waist more than BMI, useful as an early-warning nudge.
Frame Size Calculator
Small, medium or large frame from wrist circumference. Helps interpret ideal-weight calculators in proportion to your bone structure.
Alcohol Units Calculator
Convert ml and ABV into UK-style alcohol units, useful for tracking the 14-units-per-week guideline.
Carbohydrate Need Calculator
How many grams of carbs you need per day for energy, from minimum brain function up to endurance-training loads.
Fat Intake Calculator
Daily fat grams spanning from the AMDR floor of 20% up to a ketogenic ceiling, by calorie target.
Water Need by Weight
Get a tailored daily water target for your weight and the climate you live in. Hotter climate, more water.
Caffeine Safe Limit Calculator
The 400 mg/day adult ceiling is a population guideline. Use your weight to estimate a more personal upper bound.
Sleep Need by Age
Recommended hours of sleep per night by age bracket, based on the NSF consensus and recent meta-analyses.
Daily Sugar Limit Calculator
WHO recommends free sugars stay under 10% of calories (5% ideal). Plug your calories in and see the gram ceiling.
BMR (Harris-Benedict) Calculator
The original Harris-Benedict formula, revised in 1984. Compare it to the Mifflin-St Jeor estimate to see the range.
BMI Calculator (Imperial)
Calculate BMI from pounds and inches with a weight-category readout. Free, no signup.
Target Weight Calculator
Find the weekly loss or gain needed to hit your goal weight. Free, no signup.