Ideal Weight, Body Fat & Water Intake Calculator
Estimate your ideal body weight, body fat percentage, and recommended daily water intake — all in one place.
Your measurements
Waist and neck measured at their narrowest point; hip (women only) at its widest.
Estimated Body Fat
21.4%
Body fat range
- CCopy result
- DDownload PDF
- SSave this calculation
- HToggle history
- ?Show this panel
- EscClose open panel
Disabled while typing in a field.
Last updated: August 25, 2026 · Reviewed by the DoCalc team
Three Numbers, One Tape Measure
Ideal weight, body fat percentage, and daily water needs are three of the most-searched body composition questions — and all three can be estimated from measurements you can take at home with a scale and a tape measure. This calculator runs all three at once from the same inputs.
Ideal Weight — the Devine Formula
The Devine formula is a long-standing clinical estimate (originally developed for medication dosing) that's since become a widely used general reference point for "ideal" weight based on height alone. It doesn't account for frame size, muscle mass, or body composition, so treat it as a reference range, not a target to hit exactly.
Body Fat — the U.S. Navy Method
This method estimates body fat percentage from waist and neck circumference (plus hip circumference for women), and height — the same method the U.S. Navy uses for body composition screening, since it needs no special equipment beyond a tape measure. It's an estimate, typically within a few percentage points of more precise methods like DEXA scans, but not a medical-grade measurement.
Worth knowing: Measure waist and neck at their narrowest point, and (for women) hip at its widest — measuring at the wrong spot is the most common source of error in this method.
Daily Water Intake
The water intake figure uses a commonly cited guideline of about 33 ml per kilogram of body weight per day. It's a reasonable starting point for a sedentary adult in a temperate climate — actual needs go up with exercise, heat, altitude, and other factors, and some of your daily water also comes from food.
Body Fat Ranges
| Category | Men | Women |
|---|---|---|
| Essential fat | 2-5% | 10-13% |
| Athletic | 6-13% | 14-20% |
| Fitness | 14-17% | 21-24% |
| Average | 18-24% | 25-31% |
| Above average | 25%+ | 32%+ |
Frequently Asked Questions
How is body fat percentage calculated here?
Using the U.S. Navy method, which estimates body fat from waist and neck circumference (plus hip for women), and height — no special equipment needed beyond a tape measure.
How accurate is the Navy body fat method?
It's a widely used estimate, typically within a few percentage points of more precise methods like DEXA scans, but it's still an estimate — not a medical measurement.
What formula is used for ideal weight?
The Devine formula, a long-standing clinical estimate: 50 + 2.3 kg per inch over 5 feet for men, 45.5 + 2.3 kg per inch over 5 feet for women.
How is daily water intake calculated?
Using a commonly cited guideline of about 33 ml of water per kilogram of body weight per day — actual needs vary with activity level, climate, and overall health.
Is this medical advice?
No — these are general estimates for informational purposes only, not a substitute for professional medical or nutritional advice.