Health & Fitness Glossary
Clear, concise definitions of the key health and fitness terms used across our calculators. Browse alphabetically or jump to a letter below.
B
- BAC (Blood Alcohol Content)
- A measurement of the amount of alcohol in your bloodstream, expressed as a percentage by weight. A BAC of 0.08% is the legal limit for driving in most U.S. states. BAC depends on the amount consumed, body weight, biological sex, and time elapsed since drinking. Calculate yours
- BMI (Body Mass Index)
- A numerical value derived by dividing your weight in kilograms by your height in meters squared. BMI is used worldwide as a quick screening tool to classify adults into weight categories — underweight, healthy weight, overweight, and obese — that may correlate with health risks. Calculate yours
- BMR (Basal Metabolic Rate)
- The number of calories your body requires at complete rest to maintain basic life-sustaining functions such as breathing, circulation, and cell production. BMR typically accounts for 60-75% of your total daily energy expenditure and is commonly estimated using the Mifflin-St Jeor equation. Calculate yours
- Body Composition
- The proportions of fat, muscle, bone, water, and other tissues that make up your total body weight. Unlike weight or BMI alone, body composition provides a detailed view of what your body is made of, helping you assess health and fitness more accurately.
- Body Fat Percentage
- The proportion of your total body weight that is fat tissue, expressed as a percentage. Healthy ranges are approximately 10-20% for men and 18-28% for women. It is a more informative health metric than weight or BMI alone because it distinguishes fat mass from lean mass. Calculate yours
C
- Calorie
- A unit of energy. In nutrition, "calorie" typically refers to a kilocalorie (kcal) — the energy needed to raise the temperature of one kilogram of water by one degree Celsius. Your body uses calories from food for all functions, from breathing to intense exercise. Calculate yours
- Calorie Deficit
- A state in which you consume fewer calories than your body burns, forcing it to use stored energy (primarily body fat) for fuel. A moderate deficit of 500 calories per day typically results in about one pound of fat loss per week. Calculate yours
- Calorie Surplus
- A state in which you consume more calories than your body burns, providing excess energy for tissue growth. A controlled surplus of 250-500 calories per day is commonly used to support muscle gain during a strength training program. Calculate yours
- Carbohydrate
- One of the three macronutrients, providing 4 calories per gram. Carbohydrates are the body's preferred fuel source for high-intensity exercise and brain function. They are found in grains, fruits, vegetables, legumes, and dairy products. Calculate yours
- Circumference Measurement
- A body measurement taken around a specific body part (such as the waist, hips, or neck) using a flexible tape measure. Circumference measurements are used in formulas like the Navy body fat method and the Army tape test to estimate body fat percentage without specialized equipment.
- Cooper Test
- A 12-minute running test used to estimate VO2 max. You run as far as possible in 12 minutes, and the distance covered is used in a formula to estimate your maximal oxygen uptake. It was developed by Dr. Kenneth Cooper in 1968 for military fitness assessment. Calculate yours
D
- Due Date (Estimated Date of Delivery)
- The projected date of birth for a pregnancy, typically calculated as 280 days (40 weeks) from the first day of the last menstrual period using Naegele's Rule. Only about 5% of babies are born on their exact due date; most arrive within two weeks before or after. Calculate yours
E
- Epley Formula
- A widely used formula for estimating one rep max (1RM) from the weight lifted and the number of repetitions performed: 1RM = weight x (1 + reps / 30). It is most accurate when using sets of 10 or fewer reps. Calculate yours
- Essential Fat
- The minimum amount of body fat necessary for normal physiological function, including hormone regulation, vitamin absorption, and organ protection. Essential fat is approximately 2-5% of body weight for men and 10-13% for women. Going below these levels can cause serious health consequences.
F
- Fat (Dietary)
- One of the three macronutrients, providing 9 calories per gram — the most energy-dense macronutrient. Dietary fat is essential for hormone production, cell membrane integrity, and absorption of fat-soluble vitamins (A, D, E, K). Sources include oils, nuts, avocados, and fatty fish. Calculate yours
- Fiber
- A type of carbohydrate that the body cannot fully digest. Fiber supports digestive health, helps regulate blood sugar, and promotes satiety. The recommended daily intake is 25 grams for women and 38 grams for men. Found in whole grains, fruits, vegetables, and legumes. Calculate yours
H
- Heart Rate Reserve (HRR)
- The difference between your maximum heart rate and your resting heart rate. HRR represents the range of heart rate available for exercise and is used in the Karvonen formula to calculate personalized training zones. A larger HRR generally indicates better cardiovascular fitness. Calculate yours
- Heart Rate Zone
- A range of heartbeats per minute that corresponds to a specific exercise intensity level. There are typically five zones, from Zone 1 (very light, 50-60% of max) to Zone 5 (maximum effort, 90-100% of max). Training in different zones targets different fitness adaptations. Calculate yours
I
- Ideal Weight
- A theoretical weight range considered healthy for your height and sex, estimated using clinical formulas such as Devine, Robinson, Miller, and Hamwi. Ideal weight is a general guideline; individual health depends on many factors including body composition, fitness level, and medical history. Calculate yours
- IOM Guidelines (Pregnancy Weight Gain)
- Recommendations from the Institute of Medicine (now the National Academy of Medicine) for total pregnancy weight gain based on pre-pregnancy BMI. The guidelines help optimize outcomes for both mother and baby: 28-40 lbs for underweight, 25-35 lbs for normal weight, 15-25 lbs for overweight, and 11-20 lbs for obese women. Calculate yours
K
- Karvonen Formula
- A method for calculating target heart rate training zones that accounts for both maximum and resting heart rates. The formula is: Target HR = ((Max HR - Resting HR) x % Intensity) + Resting HR. It is considered more personalized than simple percentage-of-max methods. Calculate yours
L
- Lean Body Mass (LBM)
- Your total body weight minus all fat mass. LBM includes muscle, bone, organs, water, and connective tissue. Knowing your LBM helps set more accurate calorie and protein targets and distinguishes between fat loss and muscle loss during a diet. Calculate yours
- LMP (Last Menstrual Period)
- The first day of the most recent menstrual period, used as the starting point for calculating gestational age and estimating due dates. Most pregnancy dating methods — including Naegele's Rule — count from the LMP rather than the date of conception. Calculate yours
M
- Macro (Macronutrient)
- One of the three nutrients that provide calories: protein (4 cal/g), carbohydrates (4 cal/g), and fat (9 cal/g). "Tracking macros" means monitoring the grams of each macronutrient you consume to optimize body composition, performance, or health outcomes. Calculate yours
- MET (Metabolic Equivalent of Task)
- A unit that expresses the energy cost of a physical activity relative to rest. One MET equals the energy expenditure of sitting quietly (approximately 3.5 ml of oxygen per kg of body weight per minute). Walking briskly is about 3.5 METs, while running at 6 mph is about 10 METs. Calculate yours
- Mifflin-St Jeor Equation
- A formula developed in 1990 for estimating Basal Metabolic Rate (BMR) based on weight, height, age, and sex. It is considered the most accurate BMR prediction equation for most adults and is recommended by the Academy of Nutrition and Dietetics. Calculate yours
N
- Naegele's Rule
- A standard method for estimating a pregnancy due date. Starting from the first day of the last menstrual period, add one year, subtract three months, and add seven days. This is equivalent to adding 280 days (40 weeks) and assumes a regular 28-day menstrual cycle. Calculate yours
- Navy Method (Body Fat)
- A body fat estimation method developed by the U.S. Navy that uses circumference measurements of the neck, waist, and (for women) hips, along with height. It is accurate to within 3-4% of hydrostatic weighing for most people and requires only a tape measure. Calculate yours
O
- One Rep Max (1RM)
- The maximum weight you can lift for a single repetition of a given exercise with proper form. The 1RM is the standard reference point for strength training programs, as training loads are typically prescribed as percentages of your 1RM (e.g., 70% for hypertrophy). Calculate yours
P
- Pace (Running)
- The time it takes to cover a unit of distance while running, typically expressed as minutes per mile or minutes per kilometer. For example, a 5:00/km pace means it takes five minutes to run each kilometer. Pace is the inverse of speed and is the standard metric used by distance runners. Calculate yours
- Protein
- One of the three macronutrients, providing 4 calories per gram. Protein is essential for building and repairing muscle tissue, producing enzymes and hormones, and supporting immune function. Common sources include meat, fish, eggs, dairy, legumes, and tofu. Calculate yours
R
- Resting Heart Rate (RHR)
- The number of times your heart beats per minute while at complete rest. A normal resting heart rate for adults is 60-100 bpm, while well-trained endurance athletes may have RHR as low as 40 bpm. A lower RHR generally indicates more efficient heart function. Calculate yours
- Rockport Walk Test
- A submaximal fitness test used to estimate VO2 max by walking one mile as quickly as possible on a flat surface and recording your time and heart rate at the finish. It is a safer alternative to maximal exertion tests and is suitable for a wide range of fitness levels. Calculate yours
S
- Sleep Cycle
- A complete progression through all stages of sleep — light sleep (N1, N2), deep sleep (N3), and REM sleep — lasting approximately 90 minutes. Most people complete 4-6 cycles per night. Aligning your alarm with the end of a cycle helps you wake feeling more refreshed. Calculate yours
T
- TDEE (Total Daily Energy Expenditure)
- The total number of calories your body burns in a 24-hour period, including your BMR, physical activity, non-exercise activity thermogenesis (NEAT), and the thermic effect of food. TDEE is the key number for managing weight: eat below it to lose, above it to gain, or match it to maintain. Calculate yours
- Trimester
- One of the three roughly equal stages of pregnancy. The first trimester (weeks 1-13) involves organ formation, the second trimester (weeks 14-27) is a period of rapid growth, and the third trimester (weeks 28-40) prepares the baby for birth. Each trimester has distinct developmental milestones and maternal health considerations. Calculate yours
V
- VO2 Max
- The maximum rate at which your body can consume oxygen during intense exercise, expressed in milliliters of oxygen per kilogram of body weight per minute (ml/kg/min). It is the gold standard measure of aerobic cardiovascular fitness and can be estimated using field tests like the Cooper test or Rockport walk test. Calculate yours
W
- Waist-to-Hip Ratio (WHR)
- A measurement calculated by dividing your waist circumference by your hip circumference. WHR is an indicator of fat distribution and associated health risk. The WHO classifies a WHR above 0.90 for men and 0.85 for women as indicating substantially increased risk of metabolic complications. Calculate yours
- Widmark Formula
- A pharmacokinetic formula used to estimate blood alcohol content (BAC) based on the amount of alcohol consumed, body weight, a sex-specific constant (Widmark factor), and time elapsed. Developed by Erik Widmark in the 1930s, it remains the most widely used BAC estimation method. Calculate yours