5-day fast
5 Day Fast Weight Loss Calculator
A 5-day water fast adds two more days of calorie deficit after the initial water drop.
The 5-day preset is selected automatically.
More fat, less water %
After day 3, water taper slows while fat loss accumulates daily.
Medical caution
Extended fasts are not appropriate for everyone.
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.