AI vs Navy Method vs DEXA — Which Body Fat Method Is Best?
If you’ve compared body fat estimates before, you’ve probably noticed something frustrating: different methods give different numbers. That doesn’t mean they’re broken — it means they answer different questions.
This guide compares AI photo estimation, the Navy Method, and DEXA scans across cost, precision, and practicality.
“Best” depends on what you care about
When people ask for the “best” body fat estimation method, they’re usually mixing three different goals:
- Precision (how close is it to a true value?)
- Consistency (can I repeat it reliably?)
- Accessibility (can I actually use it often?)
No method wins all three. The right choice depends on your use case.
The Navy Method (tape measurements)
The Navy Method estimates body fat using tape measurements of the waist, neck, and sometimes hips. It’s popular because it’s simple and requires no equipment beyond a tape measure.
The downside is that it relies on formulas and averages. Small measurement errors can change results, and it doesn’t account well for muscle mass or fat distribution.
Best for: simple, low-cost estimates if measured consistently.
DEXA scans (high precision, low frequency)
DEXA scans use X-ray imaging to estimate body composition, including fat mass, lean mass, and bone density. They’re often treated as a reference standard.
While DEXA is precise, it’s expensive, time-consuming, and impractical for frequent tracking. Results can also vary slightly between machines and facilities.
Best for: occasional baseline measurements or research-level detail.
AI photo-based body fat estimation
AI body fat estimators analyze visual cues in photos — proportions, silhouette, and fat distribution — to estimate body fat directionally.
AI doesn’t measure fat directly. Its strength is alignment with appearance and accessibility. When used consistently, it’s effective for tracking visual changes over time.
Best for: frequent check-ins, appearance-based tracking, and real-world consistency.
Quick comparison
- Cost: AI (low) → Navy (low) → DEXA (high)
- Precision: DEXA (high) → AI/Navy (moderate)
- Consistency: AI (high with setup) → Navy (medium)
- Accessibility: AI (very high) → Navy (high)
So… which body fat method is best?
If you want a precise snapshot and don’t need frequent updates, DEXA is hard to beat. If you want a simple, low-cost estimate, the Navy Method can work.
If your goal is to understand and track how your body actually looks over time, AI photo estimation is often the most practical choice.
Choose the method that fits your goal
For most people, the best method is the one they can use consistently — and interpret realistically.
FAQ
What is the most accurate body fat measurement method?
DEXA scans are generally the most precise for one-time measurement, but they’re expensive and impractical for frequent tracking. Accuracy alone doesn’t always make a method the most useful.
Is AI body fat estimation better than the Navy Method?
AI photo estimation and the Navy Method serve different purposes. The Navy Method relies on formulas and tape measurements, while AI estimation aligns more closely with visual appearance and trend tracking.
Why do different body fat methods give different results?
Each method measures or infers body fat using different signals—formulas, circumference, imaging, or visual patterns—so disagreement is normal.
Which method should I use to track progress?
The best tracking method is one you can repeat consistently. For most people, that’s a method that’s accessible, low-cost, and appearance-aligned.
Matt Mapother
Independent product builder focused on practical fitness tools, body composition, and visual progress tracking.
Last updated: January 2026