"How do I measure my body fat percentage?" has more answers than most people realize, and they don't agree with each other. A DEXA scan, a smart scale, and a tape measure can all give you three different numbers for the same body on the same day — not because one is "wrong," but because each measures a different physical property and makes different assumptions to estimate fat.
| Method | Accuracy | Typical Cost | Convenience |
|---|---|---|---|
| DEXA Scan | ±1-2% (gold standard) | $75-150 per scan | Low — clinic visit required |
| Skinfold Calipers | ±3-5% (technique-dependent) | $20-30 one-time | Medium — needs practiced technique |
| Navy Method (Tape Measure) | ±3-4% | Free | High — just a tape measure |
| BIA Smart Scale | ±5%+ (hydration-sensitive) | $30-100 one-time | Highest — step on and go |
*Accuracy figures are general published ranges and vary by specific device/technique quality. DEXA is consistently rated the most accurate across independent comparisons; BIA scales are consistently rated the most convenient but least precise for a single reading.
The Navy method needs nothing but a tape measure and gives a solid, validated estimate.
Calculate My Body Fat % 🚀Gold-standard accuracy doesn't automatically make DEXA the best tool for your situation. If you're tracking weekly progress during a cut, paying $100+ per scan isn't sustainable, and DEXA's precision is wasted if you're only checking in once every few months anyway. The Navy method or skinfold calipers, used consistently by the same person with the same technique, are often the more practical choice for frequent tracking — save DEXA for periodic "true number" check-ins every 3-6 months.
The accuracy-convenience tradeoff: the most precise methods take the most effort or money. The Navy method sits in the practical middle ground — free, fast, and reasonably accurate.
BIA scales estimate body fat by sending a small electrical current through your body and measuring resistance — fat resists current differently than muscle and water. The problem is that hydration, recent food intake, and even skin temperature all shift that resistance reading, which is why your smart scale can show a 2-3% swing between morning and evening on the same day with zero actual fat change. The Navy method's circumference measurements don't fluctuate nearly as much with hydration, which is part of why it stays in active use for military fitness standards.
Whichever method you choose, the single most important thing is staying consistent — same method, same time of day, same conditions, tracked over weeks. Comparing a morning Navy-method reading to an evening BIA scale reading isn't tracking progress, it's comparing two different rulers. Pick one method and stick with it long enough to see a real trend.
For most people tracking their own progress at home, the Navy method (free, just a tape measure) or skinfold calipers ($20-30) offer the best balance of accuracy and accessibility. Save DEXA for an occasional accuracy check-in if you want to validate your home method's trend.
If you're using a circumference or BIA-based method, gaining muscle can sometimes show as a slight increase in measured body fat %, since these methods are estimates based on indirect proxies, not direct fat measurement. A DEXA scan would more reliably separate the muscle gain from any actual fat change.
For BIA scales, yes — measuring first thing in the morning before eating or drinking gives the most consistent reading. For the Navy method and skinfold calipers, fasting matters less, but consistent timing still helps reduce day-to-day measurement noise.