Science-backed fitness calculators that run 100% on your device. Get clear estimates, practical guidance, and tools designed for everyday fitness goals.
Every key fitness metric — one tool, zero friction
BMI Calculator
Body Mass Index from height & weight
TDEE Calculator
Total daily energy expenditure
BMR Calculator
Calories burned at complete rest
Body Fat %
US Navy circumference method
Ideal Weight
Based on 5 medical formulas
Calorie Target
Daily calories for your goal
Macro Split
Protein, carbs & fat breakdown
Water Intake
Daily hydration goal
Heart Rate Zones
Training intensity zones
Lean Body Mass
Muscle vs fat mass estimate
1-Rep Max
Max strength & training percentages
Protein Intake
Daily target by weight & goal
Sleep Cycles
Ideal bed & wake-up times
Sleep Debt
Accumulated deficit & recovery plan
Running Pace
Pace splits & race predictions
Army Body Fat
Official military circumference test
Calorie Deficit
Daily targets & fat loss timeline
Biological Fitness Age
Cardiovascular fitness score
Free Resource · No Spam
Enter your email and we'll send a free, practical guide built around your exact fitness metrics — nutrition, training, and recovery. One email per week. Unsubscribe anytime.
Free forever. No spam. Privacy policy.
Why CalaiFitness
Every calculation runs entirely in your browser using JavaScript. No data is ever sent to our servers, logged, or sold. What you enter stays on your device — always.
0 bytes
sent to servers
We use only peer-reviewed formulas: Mifflin-St Jeor for BMR/TDEE, the US Navy method for body fat, WHO BMI standards, and the Karvonen formula for heart rate zones.
10+
validated formulas
Your results are saved automatically to your browser's local storage. Open the dashboard to see your history and track how your numbers change week over week.
100%
on-device storage
Simple by Design
Pick from 18 free calculators covering every key fitness metric — from BMI to body fat to daily calories.
Input your measurements in metric or imperial units. Our clean, distraction-free interface takes seconds to fill out.
Results appear immediately, with context, categories, and advice. Save to history to track your progress over time.
Quick Answers
TDEE (Total Daily Energy Expenditure) is the total calories your body burns each day, including activity. It's the most important number in nutrition — knowing it lets you set an exact calorie target for fat loss, maintenance, or muscle gain.
Learn more →BMI is accurate as a population-level screening tool for adults. It has known limitations for athletes and older adults due to muscle mass differences. For a complete picture, pair it with body fat percentage.
Learn more →Completely private. All calculations run in your browser — nothing is ever sent to our servers. We have no database of user data. Your history is stored in your browser's localStorage only.
Learn more →Science-Based Articles
What is a healthy BMI for a 45-year-old woman who exercises? Discover why standard BMI charts mislead active women, ideal body fat ranges, and how to assess true health.
Read article →How many calories does a 5'6 woman need to maintain weight? Complete calorie chart by age, weight, and activity level with exact macro formulas.
Read article →Need 150 to 160 grams of protein daily? Here is how to hit your protein target easily with whole foods, budget-friendly staples, and exact meal breakdowns.
Read article →No sign-up. Results in under 30 seconds. Your calculator entries stay on your device.
