Health Calculators. Formulas you can check.
BMI, calorie need, body fat percentage, and pregnancy tools. Every formula cites its medical reference: WHO, Mifflin-St Jeor, US Navy method.
Available now
Body Mass Index with metric and imperial units. Instant category lookup against WHO ranges.
Daily calorie target for weight loss, maintenance, or muscle gain, with an estimated timeline.
Basal Metabolic Rate via Mifflin-St Jeor: calories burned at rest.
Total Daily Energy Expenditure by activity level, with maintenance calories and macros.
Body fat percentage via the US Navy tape method, with ACE category ranges.
Healthy weight range for your height: Devine, Robinson, Miller, Hamwi and BMI.
Daily water need from body weight, activity level and climate.
Due date, current week and trimester from your last period (Naegele's rule).
Your fertile window and estimated ovulation date from your cycle.
Coming soon
Protein, carb and fat gram targets from your daily calorie goal.
About Calctube health tools
Calctube's health calculators target the most-searched fitness and clinical estimators on the web: BMI, calorie need, BMR, body fat percentage, TDEE, and pregnancy due date. Every page shows the exact formula and the medical reference behind it. Calculations run in your browser; we never see or store your inputs.
These tools are designed for healthy adults and produce reasonable estimates only. They are not a substitute for clinical assessment, prescription, or diagnosis by a qualified physician.
Frequently asked questions
Are Calctube health calculators medically accurate?
Our formulas are sourced from established medical references: WHO BMI ranges, Mifflin-St Jeor for BMR, US Navy for body fat. They produce reasonable estimates for healthy adults but are not a substitute for clinical assessment by a doctor.
Why does the BMI calculator give different categories for the same weight?
BMI categories depend on the population standards selected. We default to WHO global ranges (underweight <18.5, normal 18.5–24.9, overweight 25–29.9, obese 30+). Asian populations use stricter cutoffs (overweight 23+, obese 27.5+) per WHO Asia-Pacific guidance. Toggle this on the BMI page.
Do you store any of my health data?
No. All calculations run entirely in your browser. We never see your height, weight, age, or any other input. There is no account or login.