Health & Fitness Calculators

ArrayKit's health calculators apply standard formulas to fitness, nutrition and pregnancy numbers. For weight and energy, the BMI Calculator divides weight by height squared and gives the healthy weight range, the Calorie Calculator and TDEE Calculator multiply a Mifflin-St Jeor resting rate by an activity level, the BMR Calculator shows that resting rate alone, and the Macro Calculator splits a calorie total into protein, carb and fat grams. The Body Fat Calculator applies the US Navy tape-measure method. For pregnancy and cycles, the Due Date Calculator adds 280 days to the first day of the last period, the Pregnancy Calculator shows weeks, trimester and progress, the Ovulation Calculator and Period Calculator project fertile windows and upcoming periods, and the Conception Calculator works back to a likely conception date. For training, the Pace Calculator, One Rep Max Calculator, Target Heart Rate Calculator and Calories Burned Calculator cover running pace, 1RM, heart rate zones and MET-based calorie burn. The Protein Calculator and Water Intake Calculator turn body weight into daily targets, while the GFR Calculator (CKD-EPI 2021) and BAC Calculator (Widmark formula) apply published equations to a creatinine result or drink count. People tracking fitness or a pregnancy, coaches and students use them to check the math. Results are estimates, not medical advice, and every calculation runs in your browser, so the measurements and dates you enter stay on your device.

• BMI Calculator — Calculate body mass index and see the healthy weight range for your height.
• BMR Calculator — Estimate your basal metabolic rate — the calories your body burns at rest.
• TDEE Calculator — Estimate total daily energy expenditure from BMR and activity level.
• Calorie Calculator — Estimate daily calories to maintain, lose or gain weight from your stats.
• Macro Calculator — Split your daily calories into protein, carbs and fat grams by ratio.
• Protein Calculator — Estimate your daily protein needs from weight and activity level.
• Carbohydrate Calculator — Estimate daily carbohydrate grams from your calories and diet split.
• Fat Intake Calculator — Estimate daily dietary fat grams from your calories and target percentage.
• Body Fat Calculator — Estimate body fat percentage with the US Navy tape measurement method.
• Army Body Fat Calculator — Estimate body fat with the US Army (AR 600-9) circumference method.
• Lean Body Mass Calculator — Estimate lean body mass and fat mass from height, weight and sex.
• Ideal Weight Calculator — Estimate ideal body weight with the Devine, Robinson, Miller and Hamwi formulas.
• Healthy Weight Calculator — Find the healthy weight range for your height from the normal BMI band.
• Body Type Calculator — Estimate your body shape from bust, waist and hip measurements.
• Body Surface Area Calculator — Estimate body surface area (BSA) with Mosteller, Du Bois and other formulas.
• Calories Burned Calculator — Estimate calories burned by activity using MET values, weight and time.
• Pace Calculator — Calculate running pace, time or distance and convert between pace units.
• One Rep Max Calculator — Estimate your one-rep max from a weight and reps with several formulas.
• Target Heart Rate Calculator — Find your target heart-rate training zones from age and resting rate.
• GFR Calculator — Estimate glomerular filtration rate (eGFR) with the CKD-EPI 2021 equation.
• BAC Calculator — Estimate blood alcohol content from drinks, weight, sex and time.
• Due Date Calculator — Estimate a pregnancy due date from the last menstrual period (Naegele’s rule).
• Pregnancy Calculator — Track pregnancy progress, trimester and milestones from the due date or LMP.
• Ovulation Calculator — Estimate your fertile window and ovulation day from your cycle.
• Conception Calculator — Estimate the likely conception date from a due date or last period.
• Period Calculator — Predict your next several periods and fertile windows from your cycle.
• Pregnancy Weight Gain Calculator — Estimate a healthy pregnancy weight-gain range from pre-pregnancy BMI.
• Pregnancy Conception Calculator — Estimate the conception date and fertile window from a known pregnancy.
• Water Intake Calculator — Daily water target from weight, exercise and climate, in glasses and bottles.

Guides

• Body Mass Index (BMI), Explained — The BMI formula in metric and imperial units, what a healthy BMI is for adults, the WHO categories, and why BMI is only a screening number with real limits.
• Daily Calorie Needs, Explained — How many calories you need a day: BMR vs TDEE, the Mifflin–St Jeor formula, activity multipliers, and what a 250 or 500 calorie deficit means in practice.
• METs and Calories Burned, Explained — What a MET is, the formula for calories burned (MET × 3.5 × kg ÷ 200 per minute), the Compendium of Physical Activities, and why fitness trackers disagree.
• Pregnancy Due Dates, Explained — How a due date is calculated: Naegele's rule (LMP plus 280 days), cycle length, conception and IVF dates, early ultrasound, and why few babies arrive on it.

Frequently asked questions

What can I calculate with these health calculators?

They cover body measures (BMI, healthy and ideal weight, body fat by the US Navy and Army tape methods, lean body mass, body shape and body surface area), energy and nutrition (BMR, TDEE, daily calories, macros, protein, carbohydrate, fat and water), training (calories burned, running pace, one-rep max and heart rate zones) and pregnancy and cycle dates. The GFR Calculator estimates kidney filtration (eGFR) from a creatinine result, age and sex, and the BAC Calculator estimates blood alcohol from drinks, body weight, sex and time.

How do the BMI, BMR, TDEE and calorie calculators differ?

The BMI Calculator compares weight with height (kg ÷ m²) and places the result in the adult WHO bands, where 18.5 to 24.9 is the normal range. The BMR Calculator estimates the calories burned at rest with the Mifflin-St Jeor equation, the TDEE Calculator multiplies that by an activity factor from 1.2 to 1.9, and the Calorie Calculator adds or subtracts 250 or 500 calories a day for a weight goal. The Macro Calculator then turns any calorie figure into protein, carb and fat grams.

What is the difference between the pregnancy and cycle calculators?

The Due Date Calculator estimates a due date from the first day of the last period, a conception date or an IVF transfer date, and the Pregnancy Calculator shows how many weeks along a pregnancy is and which trimester it is in. The Ovulation Calculator and Period Calculator project ovulation, fertile windows and upcoming periods from the cycle length, while the Conception Calculator and Pregnancy Conception Calculator work backwards from a due date, last period or ultrasound scan to a likely conception date. The Pregnancy Weight Gain Calculator shows the IOM weight-gain range for a pre-pregnancy BMI.

Are my measurements and dates uploaded anywhere?

No. Every health calculator runs in your browser, so weight, height, cycle dates, lab values and the other figures you enter are processed on your device and are not uploaded to ArrayKit.

Are the results medical advice, and how accurate are they?

No. Each calculator applies a published formula, such as Mifflin-St Jeor for calories, the US Navy method for body fat, Naegele's rule for due dates or CKD-EPI 2021 for eGFR, and the result is an estimate for an average person with the same inputs. Formulas do not see individual factors such as muscle mass, irregular cycles, medications or medical conditions, and the BAC Calculator is a rough guide that must never be used to decide whether to drive. For decisions about your health, talk to a doctor or another qualified professional.