Health calculators
Calculators for the numbers your body runs on: how much to eat to lose or keep weight, how much protein and water you need, where you are in your cycle, how a dose scales with a child’s weight. Each one names the formula and the study or guideline behind it, and flags the situations where a calculator is not enough and a clinician is. They are tools for planning, not medical advice.
Most used
- BAC calculator
Estimate your blood alcohol content from drinks, drink size, strength, weight, sex and hours since you started. See how you compare to driving limits and how long until you are sober.
- Calorie deficit calculator
Set a target weight and a deadline to see how many calories to eat per day, or set your calories to see when you will get there. With a safe-pace check and a week-by-week plan.
- Period calculator
Enter the first day of your last period and your cycle length to see when your next period is due, your current cycle phase, and the next six months of dates.
- Protein calculator
Find your daily protein target in grams based on weight and goal: fat loss, muscle gain, general health, endurance or age. With a per-meal split and food equivalents.
Calories and body composition
- Calorie deficit calculator
Set a target weight and a deadline to see how many calories to eat per day, or set your calories to see when you will get there. With a safe-pace check and a week-by-week plan.
- FFMI calculator
Calculate your fat-free mass index from weight, height and body fat. See where you sit on the FFMI scale, your lean mass, and how much muscle you could still add naturally.
- TDEE calculator
Find out how many calories you burn per day, and how much to eat to lose, keep or gain weight. Uses the Mifflin-St Jeor equation.
Nutrition
- Protein calculator
Find your daily protein target in grams based on weight and goal: fat loss, muscle gain, general health, endurance or age. With a per-meal split and food equivalents.
- Water intake calculator
Work out how much water to drink per day from your weight, age, exercise, climate and pregnancy. Result in litres, ounces and glasses, with a simple daily schedule.
Cycle and fertility
- Ovulation calculator
Find your estimated ovulation date and fertile window from your last period and cycle length. Day-by-day chances, when to test, and the due date if you conceive this cycle.
- Period calculator
Enter the first day of your last period and your cycle length to see when your next period is due, your current cycle phase, and the next six months of dates.
Safety and dosing
- BAC calculator
Estimate your blood alcohol content from drinks, drink size, strength, weight, sex and hours since you started. See how you compare to driving limits and how long until you are sober.
- Infant Tylenol dosage calculator
Find the right dose of infant or children's Tylenol (acetaminophen) by weight, in mL or tablets for the product you have. Based on the AAP dosing table, with the 24-hour maximum and safety checks.
- Sobriety calculator
Count your days, weeks and months sober from your sobriety date, see your next milestone dates, and what you have saved in drinks, money and calories.
Questions about these calculators
Are these health calculators medically reviewed?
Every formula comes from a published source cited on the page, such as the Mifflin-St Jeor equation or the American Academy of Pediatrics dosing table, and each page shows when it was last checked. They are planning tools, not a substitute for a doctor, and the pages say when to call one.
Do you store my health data?
No. Everything is calculated in your browser and nothing is sent to a server. A shared link contains only the numbers you chose to put in it.
Metric or imperial?
Both. The default follows your browser’s region and you can switch at the top of each calculator.