30 free tools
Health and fitness calculators
Most fitness math is simple once you see the formula. BMI is weight divided by height squared. A 500-calorie daily deficit is about a pound a week, at least at first. Protein and carbs carry 4 calories per gram and fat carries 9. These calculators do the arithmetic and explain what the numbers mean.
All health tools
A1C Calculator
Convert A1C to estimated average glucose in mg/dL or mmol/L, or back again, with the ADAG formula. See your ADA range and a full A1C chart.
BMI Calculator
BMI calculator for adults using feet and pounds or cm and kg. Shows your CDC weight category and the healthy weight range for your height.
BMR Calculator
BMR calculator using the Mifflin-St Jeor equation. Get the calories you burn at rest plus daily maintenance calories for five activity levels.
Body Fat Calculator
Body fat calculator using the US Navy tape-measure method. Enter neck, waist, and hip to get body fat %, fat mass, lean mass, and your ACE category.
Body Surface Area Calculator
Calculate body surface area (BSA) in m² with the Mosteller and Du Bois formulas side by side. Enter height and weight in inches and pounds or metric.
Calorie Deficit Calculator
Calorie deficit calculator that turns your maintenance calories into a daily target, weekly deficit, and estimated pounds lost. Warns on unsafe targets.
Calories Burned Calculator
Estimate calories burned for over 1,100 activities, from running to yard work, using MET values from the 2024 Compendium of Physical Activities.
Conception Calculator
Estimate your conception date and fertile window from your last period or due date, including ultrasound dates. See the likely range, not just one day.
FFMI Calculator
Calculate your fat-free mass index (FFMI) and height-normalized FFMI from height, weight, and body fat %. Compare to Kouri's natural limit of 25.
Heart Rate Zone Calculator
Find your 5 heart rate training zones by % of max HR and the Karvonen reserve method. Uses Tanaka or 220 - age, or your measured max heart rate.
Ideal Weight Calculator
Compare ideal body weight from the Devine, Robinson, Miller, and Hamwi formulas side by side, plus the healthy BMI weight range for your height and sex.
Implantation Calculator
Estimate your implantation window from your last period or ovulation date. See the full 6-12 DPO range, the most likely days, and when to take a test.
Lean Body Mass Calculator
Estimate lean body mass with the Boer, James, and Hume formulas, or from your body fat %. Compare results in pounds or kg and see implied body fat.
Macro Calculator
Macro calculator that turns your daily calories into protein, carb, and fat grams. Pick keto, low carb, high protein, or a custom split.
One Rep Max Calculator
Estimate your one rep max from any set of 1-12 reps with the Epley and Brzycki formulas side by side, plus a percentage of 1RM table rounded for plates.
Ovulation Calculator
Ovulation calculator that predicts your fertile window, ovulation day, and next period for three cycles from your last period and cycle length.
Pace Calculator
Pace calculator for runners: enter distance and time to get pace per mile and per km, speed, and finish times for 5K, 10K, half and full marathon.
Period Calculator
Predict your next period and the next 6 cycles from your last period and cycle length. Average past cycles for a likely date range. Nothing is stored.
Pregnancy Due Date Calculator
Due date calculator: estimate your pregnancy due date from your last period and cycle length, and see how many weeks pregnant you are today.
Pregnancy Test Calculator
Find the earliest and most reliable day to take a pregnancy test from your last period, ovulation date, or date of sex, with a day-by-day DPO timeline.
Pregnancy Weight Gain Calculator
See your recommended pregnancy weight gain by week from your pre-pregnancy BMI, using IOM 2009 guidelines. Covers one baby or twins, in lb or kg.
Protein Calculator
Find your daily protein target in grams from body weight and goal, using RDA, ISSN, and research ranges. Includes a per-meal split and goal-weight option.
Sleep Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles so you wake up between cycles feeling refreshed, not groggy.
Steps to Calories Calculator
Estimate calories burned from your daily steps using weight, height, and walking pace with MET values from the 2024 Compendium. Shows total and net kcal.
Steps to Miles Calculator
Convert steps to miles or kilometers using your height and sex, or your measured step length. See your steps per mile and a steps-per-mile chart by height.
TDEE Calculator
TDEE calculator in pounds and inches. Get maintenance calories, BMR, and daily targets to lose 1 lb or gain 0.5 lb a week. Free, no sign-up.
VO2 Max Calculator
Estimate VO2 max three ways: the Cooper 12-minute run, the 1.5-mile run test, and the resting heart rate ratio method. Formulas shown, miles or meters.
Waist to Height Ratio Calculator
Calculate your waist-to-height ratio, see the NICE health band, and check the 2026 US Army WHtR standard (below 0.55). Inches or centimeters.
Water Intake Calculator
Water intake calculator: get a daily target in ounces, cups, and liters from your weight in pounds and active minutes. Free, no sign-up.
Weight Loss Goal Date Calculator
See the date you'll reach your goal weight on a set calorie intake. Maintenance is recalculated as you lose, so the date is realistic, not 3,500-rule math.
About these tools
Use them to estimate BMI and body fat, set a calorie target for weight loss, split calories into protein, carbs, and fat, and plan daily water intake. Each page covers where the estimate breaks down, such as BMI misreading muscular athletes or the 3,500-calorie rule overestimating long-term loss.
Your measurements stay in your browser and are never stored. These are general estimates for education, not medical advice. If you have a health condition, are pregnant, or are making a big change to your diet, talk to a doctor or registered dietitian.