Health Calculators
Track your wellness easily using our BMI calculator, calorie calculator, and water intake calculator. These tools are designed to support balanced living and accurate self-assessment.
About Our Health Calculators
Every health tool here runs on a named, documented method — not a black box. BMI uses the WHO/NIH classification (18.5–24.9 healthy range), calorie and TDEE estimates use the Mifflin-St Jeor equation published in the American Journal of Clinical Nutrition in 1990, and body fat uses the U.S. Navy circumference formulas from the Naval Health Research Center. Each calculator page states its formula, shows a worked example, and links to the primary source so you can check our math.
The honest caveat: these are screening estimates, not diagnoses. Equations built on population averages can misread individuals — a muscular person's BMI overstates their fat, and any BMR equation can miss by ±10%. Use the numbers as a starting point and confirm health decisions with a professional.
All 36 Health Calculators
- Army Body Fat Calculator Calculate your body fat the way the U.S. Army does: the official one-site tape test from AR 600-9. Enter weight and abdo…
- BAC Calculator Estimate blood alcohol content from standard drinks, body weight, and time (Widmark formula, NIAAA 14-g standard drink) …
- BMI Calculator Calculate your Body Mass Index (BMI) to assess potential health risks like diabetes & heart disease. Track your fitness …
- BMR Calculator Your basal metabolic rate by the Mifflin-St Jeor equation — the clinically preferred formula — with the activity-multipl…
- Body Fat Calculator Use our Body Fat Calculator to find your body fat percentage. Track fat loss, muscle gain, and fitness progress using ac…
- Body Fat Percentage Calculator Calculate your Body Fat Percentage using the U.S. Navy method or BMI-based formula. Get an accurate measure of fat vs. m…
- Bra Size Calculator Find your bra size from two tape measurements — underbust and bust — with the standard band-and-cup method, sister sizes…
- Calorie Calculator Use the Calorie Calculator on Vast Calculators to find out how many calories you need daily to maintain, lose, or gain w…
- Calorie Deficit Calculator Turn your maintenance calories into a daily target for 0.5–2 lb/week of loss — with the 3,500-kcal convention explained …
- Calories Burned Calculator Calories burned for 15 common activities using Compendium MET values — the standard MET formula, per-hour burn rates by …
- Carbohydrate Calculator Turn your daily calories into a carbohydrate gram range — standard AMDR (45–65%), lower-carb, or keto — with the fiber a…
- Chipotle Calorie Calculator Build your exact Chipotle order — burrito, bowl, salad, or tacos — and see its calories instantly, using Chipotle's publ…
- Cow Gestation Calculator Predict a cow's calving date from breeding or AI date using standard gestation averages (279–287 days by breed type) — w…
- DEXA Body Fat Estimator What's a good DEXA body fat percentage? Estimate your body fat now with the tape method, see how it compares to a DEXA s…
- Gestational Age Calculator Work out exactly how many weeks and days pregnant you are, from your last period or a known due date — with the ACOG dat…
- Heart Rate Zone Calculator Use our Heart Rate Zone Calculator to find your ideal workout intensity. Discover your target heart rate zones for fat b…
- Height Calculator (Child Height Predictor) Predict a child's adult height from the parents' heights with the classic mid-parental (Tanner) method — the ±8.5 cm hon…
- Height Percentile Calculator Find your or your child's height percentile by age and gender, and see how the measurement compares with typical growth-…
- Horse Gestation Calculator Predict a mare's foaling date from the breeding date at 330–350-day averages — with the honest equine caveat (normal mar…
- Ideal Weight Calculator Your ideal body weight by the four classic clinical formulas plus the healthy-BMI range — with the honest history: these…
- Macro Calculator Use our Macro Calculator to find your perfect balance of protein, carbs, and fats. Plan your nutrition with accurate mac…
- NASM Calorie Calculator Calculate daily calories the way NASM-certified trainers do: BMR via the Mifflin-St Jeor equation × activity factor, wit…
- Ovulation Calculator Estimate your ovulation date and 6-day fertile window from your last period and cycle length. Standard luteal-phase meth…
- Period Calculator Predict your next three periods from your last period date and cycle length — plus estimated ovulation and fertile windo…
- Pregnancy Due Date Calculator Estimate your due date from your last period (ACOG's 280-day rule with cycle-length adjustment), conception date, or IVF…
- Pregnancy Weight Gain Calculator Healthy pregnancy weight-gain range from your pre-pregnancy BMI — official IOM/NASEM guidelines for singletons and twins…
- Protein Calculator Calculate your exact daily protein intake needed for muscle gain, fat loss, or maintenance. Science-backed formula tailo…
- Running Pace Calculator Use our Running Pace Calculator to track your speed per mile or kilometer. Perfect for runners training for 5K, 10K, or …
- Sleep Calculator Find the best time to go to bed or wake up based on 90-minute sleep cycles, with a fall-asleep buffer — plus recommended…
- Starbucks calories calculator Calculate Starbucks drink calories instantly. Customize size, milk, and toppings to see accurate calorie counts fast
- Steps to Miles Calculator Convert steps to miles (or miles to steps) using a stride length estimated from your height — with the steps-per-mile ta…
- Subway Calorie Calculator Build your Subway order — sub, size, cheese, sauce, sides — and see the calories instantly, based on Subway's published …
- Taco Bell Calorie Calculator Add up the calories in your Taco Bell order — tacos, burritos, Crunchwraps, and sides — using the chain's published U.S.…
- TDEE Calculator Use our TDEE Calculator to know how many calories you burn daily. Plan your diet, fitness, or weight goals with accurate…
- Water Intake Calculator Calculate how much water your body needs daily with Vast Calculators. Stay hydrated based on your weight, activity, and …
- Weight Percentile Calculator Determine weight percentile in seconds. Simple inputs, accurate growth tracking—perfect for parents and health monitorin…
Where Most People Start
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BMI Calculator
The 10-second health screen: weight vs height against WHO categories, with a live gauge.
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TDEE Calculator
Your daily calorie burn — the number every diet plan should be built on.
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Body Fat Calculator
Tape-measure method that lands within 3–4 points of a DEXA scan.
Health Calculators — FAQs
How accurate are these health calculators?
Each tool uses peer-reviewed or institutionally-published formulas (WHO, NIH, the Mifflin-St Jeor equation, U.S. Navy body-fat method), and every page lists its sources. Accuracy is that of the underlying equation — typically within about 10% for calorie estimates and 3–4 percentage points for tape-measure body fat. They are screening tools, not medical diagnoses.
Which calculator should I start with?
Start with BMI for a quick weight-status check, then TDEE to learn your daily calorie burn, then the Macro Calculator to split those calories into protein, carbs, and fat. That chain — status, energy, plan — covers most fitness goals.
Is my health data stored anywhere?
No. All calculations run instantly in your browser — nothing you type is sent to or saved on our servers, and you can verify results disappear on refresh.