A common at-home estimate is the U.S. Navy method, which uses your height and tape measurements of your neck, waist and, for women, hips to estimate body fat percentage. It is an estimate, not a clinical measurement. A free body fat calculator applies the formula in your browser once you enter the measurements.
The Navy method plugs circumference measurements into a formula: for men it uses waist, neck and height; for women it adds the hip measurement. Because it relies on where you carry size rather than a direct fat reading, it is a convenient estimate you can do at home with a tape measure, but it is less precise than lab methods like DEXA or hydrostatic weighing.
Body fat percentage estimates are most useful for tracking change over time under consistent conditions, rather than as a single exact number. Measure the same way each time, at the same point in the day, to make comparisons meaningful. For any health decision, a professional assessment is the right reference; this tool is a screening estimate, not medical advice.
Height and neck and waist circumference for men, plus the hip measurement for women. A flexible tape measure is enough.
It is a reasonable at-home estimate but less accurate than lab methods such as DEXA. Use it to track trends rather than as an exact figure.
No. BMI only relates weight to height, while body fat percentage estimates the share of your body that is fat. They can disagree, especially for muscular people.