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.
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 abdominal circumference, see yo...
BAC Calculator
Estimate blood alcohol content from standard drinks, body weight, and time (Widmark formula, NIAAA 14-g standard drink) — with legal-limit context...
BMI Calculator
Calculate your Body Mass Index (BMI) to assess potential health risks like diabetes & heart disease. Track your fitness goals with our free online...
BMR Calculator
Your basal metabolic rate by the Mifflin-St Jeor equation — the clinically preferred formula — with the activity-multiplier table, per-hour burn, a...
Body Fat Calculator
Use our Body Fat Calculator to find your body fat percentage. Track fat loss, muscle gain, and fitness progress using accurate measurement formulas.
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. muscle ratio for true fitnes...
Bra Size Calculator
Find your bra size from two tape measurements — underbust and bust — with the standard band-and-cup method, sister sizes, and honest fit guidance (...
Calorie Calculator
Use the Calorie Calculator on Vastcalculators.com to find out how many calories you need daily to maintain, lose, or gain weight based on your acti...
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 honestly, safety floors, an...
Calories Burned Calculator
Calories burned for 15 common activities using Compendium MET values — the standard MET formula, per-hour burn rates by weight, and honest notes on...
Carbohydrate Calculator
Turn your daily calories into a carbohydrate gram range — standard AMDR (45–65%), lower-carb, or keto — with the fiber and added-sugar guidelines b...
Chipotle Calorie Calculator
Build your exact Chipotle order — burrito, bowl, salad, or tacos — and see its calories instantly, using Chipotle's published nutrition data. Inclu...
Cow Gestation Calculator
Predict a cow's calving date from breeding or AI date using standard gestation averages (279–287 days by breed type) — with a month-by-month calvin...
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 scan (±3–4 points), and read...
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 dating convention, trimester,...
Heart Rate Zone Calculator
Use our Heart Rate Zone Calculator to find your ideal workout intensity. Discover your target heart rate zones for fat burn, endurance, and perform...
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 honest range, what actually sh...
Height Percentile Calculator
Find your or your child’s height percentile instantly. Compare age and gender accurately—try the calculator now.
Horse Gestation Calculator
Predict a mare's foaling date from the breeding date at 330–350-day averages — with the honest equine caveat (normal mares range ~320–370 days), a...
Ideal Weight Calculator
Your ideal body weight by the four classic clinical formulas plus the healthy-BMI range — with the honest history: these equations were built for d...
Macro Calculator
Use our Macro Calculator to find your perfect balance of protein, carbs, and fats. Plan your nutrition with accurate macro ratios for your fitness...
NASM Calorie Calculator
Calculate daily calories the way NASM-certified trainers do: BMR via the Mifflin-St Jeor equation × activity factor, with the goal-adjustment table...
Ovulation Calculator
Estimate your ovulation date and 6-day fertile window from your last period and cycle length. Standard luteal-phase method with ACOG/NHS-based guid...
Period Calculator
Predict your next three periods from your last period date and cycle length — plus estimated ovulation and fertile window. Uses the standard 14-day...
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 transfer day — plus how fa...
Pregnancy Weight Gain Calculator
Healthy pregnancy weight-gain range from your pre-pregnancy BMI — official IOM/NASEM guidelines for singletons and twins, plus a week-by-week targe...
Protein Calculator
Calculate your exact daily protein intake needed for muscle gain, fat loss, or maintenance. Science-backed formula tailored to your activity.
Running Pace Calculator
Use our Running Pace Calculator to track your speed per mile or kilometer. Perfect for runners training for 5K, 10K, or marathons.
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 sleep by age from AASM con...
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 table by height and the truth...
Subway Calorie Calculator
Build your Subway order — sub, size, cheese, sauce, sides — and see the calories instantly, based on Subway's published U.S. nutrition data. Includ...
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. nutrition data, with a ful...
TDEE Calculator
Use our TDEE Calculator to know how many calories you burn daily. Plan your diet, fitness, or weight goals with accurate calorie and activity insig...
Water Intake Calculator
Calculate how much water your body needs daily with VastCalculator. Stay hydrated based on your weight, activity, and lifestyle.
Weight Percentile Calculator
Determine weight percentile in seconds. Simple inputs, accurate growth tracking—perfect for parents and health monitoring.
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.
Where Most People Start
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.