Health tools built on science, not marketing.
Every calculator shows its formula, cites its sources, and explains its limitations, because you deserve to know how the number was derived.
Evidence-Based
Every tool uses a named, published formula, such as Mifflin-St Jeor, MET values, or ACC/AHA guidelines. We never use vague language like "advanced algorithm."
Transparent
Each page shows its sources, explains its limitations, and tells you what the formula can't account for. No hidden agendas.
Reviewed Regularly
Content is reviewed by our research team against current guidelines. Every page shows a "Last reviewed" date so you know when it was last verified.
Our Calculators
View All →Substance & Detection
BAC Calculator — Blood Alcohol Content Calculator
Estimate your Blood Alcohol Content (BAC) with our free calculator. Enter drinks, body weight, and time to see your estimated BAC and understand legal limits.
Vitals & Metabolic
Blood Pressure Calculator — Is My Blood Pressure Normal?
Check if your blood pressure is normal with our free blood pressure calculator. Classify your reading using ACC/AHA 2017 guidelines and understand what your numbers mean.
Body & Fitness
BMI Calculator — Body Mass Index Calculator
Calculate your Body Mass Index (BMI) instantly with our free BMI calculator. Understand what your BMI means for your health, its limitations, and better alternatives.
Body & Fitness
Body Fat Percentage Calculator — ACFT Method
Calculate your body fat percentage using the Army Combat Fitness Test (ACFT) scoring methodology. Free body composition calculator for military fitness assessment.
Body & Fitness
Body Fat Percentage Calculator — Air Force Method
Estimate your body fat percentage using the US Air Force circumference method. Free body composition calculator with height, neck, and waist measurements.
Body & Fitness
Body Fat Percentage Calculator — Army Method
Calculate your body fat percentage using the US Army circumference method (AR 600-9). Free body fat calculator with neck and waist measurements.
Why Health Is Flow?
Health Is Flow is a free health calculator hub with 18 science-based tools, from BMI and TDEE calculators to blood pressure checkers, A1C converters, hydration assessments, and more.
Every calculator shows its formula, cites its sources, and explains its limitations, because you deserve to know how the number was derived. No marketing spin, no vague "advanced algorithms."
We are not a medical practice. None of our content is medical advice. Our tools provide educational estimates based on published research, and we tell you exactly which research, so you can verify it yourself.
Our Commitment
- ✓Named formulas, not "advanced algorithms"
- ✓Cited sources with links to original research
- ✓Honest limitations for every calculator
- ✓Regular review against current guidelines
- ✓No ads, no tracking of health data
Browse Calculators by Category
Body & Fitness
BMI calculator, body fat percentage, ideal weight, one-rep max, calories burned, TDEE calculator, and macro calculator.
View all →Vitals & Metabolic
Blood pressure chart by age, A1C to blood sugar converter, water intake calculator, sleep calculator, ovulation calculator, and intermittent fasting calculator.
View all →Substance & Detection
THC detection calculator, blood alcohol content (BAC) calculator. Science-based detection time estimates with cited sources.
View all →