Age-adjusted BMR
Water Fasting Calculator by Age
Metabolism slows with age. Age must be included in the BMR equation.
Enter your age along with sex, height, and weight. Choose any fast length and click Calculate.
Mifflin-St Jeor
Industry-standard BMR formula.
Female & male
Toggle gender for the correct equation constant.
Fill in your details and click Calculate Weight Loss to see your estimated breakdown.
More water fasting calculators
Each tool uses the same science with a preset fast length—or browse our main calculator for all options, guides, and FAQs.
Also see: reference table, trusted resources, FAQ
Medical disclaimer · Estimates only—not medical advice.