💪 Health & Fitness

Health & Fitness Calculator

BMI, calories, body fat, ideal weight, macros, water and pregnancy due date — seven trusted calculators in one place, all private and instant.

Your BMI

22.9

Normal weight

Healthy weight for your height

A BMI of 18.5–24.9 puts you between 57 kg and 76 kg.

BMI is a screening tool, not a diagnosis — it doesn't distinguish muscle from fat.

These calculators provide general educational estimates and are not a substitute for professional medical advice, diagnosis or treatment. Everything runs in your browser — nothing you enter is uploaded or stored.

About this tool

Seven everyday health numbers, worked out the moment you type

The Health & Fitness Calculator bundles the seven measurements people search for most — Body Mass Index, daily calorie needs, body-fat percentage, ideal body weight, macronutrient targets, water intake and pregnancy due date — into one clean tool. Every tab uses the same published, non-proprietary formulas that doctors, dietitians and coaches rely on, so the numbers line up with what you'd get from a clinic worksheet, only instantly and without an app install.

Switch between metric and imperial with a single toggle and your entries convert automatically — no re-typing. Because everything is computed in your browser with JavaScript, nothing you enter about your body ever leaves your device: no account, no upload, no tracking of your measurements.

100% freeNo sign-upMetric & imperialPrivate — runs locally
How to use it
  1. 1Pick a calculator from the tabs — BMI, Calories, Body Fat, Ideal Weight, Macros, Water or Due Date.
  2. 2Choose metric or imperial units; your existing numbers convert for you.
  3. 3Enter your details — weight, height, age, sex or measurements as each tab asks.
  4. 4Read your result and the plain-English context instantly, and switch tabs to cross-check related numbers.
What's inside
  • BMI with healthy-weight range for your height
  • Mifflin–St Jeor calories: BMR, TDEE and lose/maintain/gain targets
  • US Navy tape-measure body-fat estimate
  • Ideal weight across the Devine, Robinson, Miller and Hamwi formulas
  • Macro split (balanced, high-protein, low-carb, keto) in grams
  • Daily water target in litres, cups and ounces
  • Pregnancy due date, gestational age and trimester (Naegele's rule)

Frequently asked questions

How is BMI calculated?
BMI is your weight in kilograms divided by the square of your height in metres (kg/m²). A BMI of 18.5–24.9 is classed as normal, 25–29.9 as overweight and 30+ as obese. It's a fast population-level screen but doesn't tell muscle from fat, so athletes often read 'overweight' despite low body fat.
Which calorie formula does this use?
The Mifflin–St Jeor equation for BMR, then multiplied by an activity factor (1.2 sedentary up to 1.9 extra-active) to get TDEE — your maintenance calories. Mifflin–St Jeor is the equation most dietitians consider the most accurate for the general population.
How accurate is the body-fat estimate?
It's the US Navy circumference method, which typically lands within 3–4% of a DEXA scan for average body types using just a tape measure. It's less accurate at the extremes (very lean or very high body fat), where a scan or callipers do better.
What's the difference between all the ideal-weight formulas?
Devine, Robinson, Miller and Hamwi are four historical equations that each map height to a 'reference' weight slightly differently. Rather than pick a winner, the tool shows all four plus the healthy-BMI weight range so you can see a sensible band instead of one falsely precise number.
Is the pregnancy due date reliable?
It uses Naegele's rule (last menstrual period + 280 days), the same starting estimate clinicians use. Only about 5% of babies arrive on the exact date, and an early ultrasound gives a more precise date, so treat it as the middle of a two-week window.
Is my data private?
Completely. Every calculation happens locally in your browser — no measurements are sent to a server, saved, or shared, and there's no login.
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Full guide

BMI, Calories & Body Fat — The Complete Guide

What each health number actually means, how the formulas work, and how to use them together to hit a goal.

BMI vs body fatCalories & TDEEMacros & waterIdeal weight formulas

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