Body fat percentage tells you something BMI cannot: how much of your weight is actually fat versus muscle, bone and water. You do not need an expensive scan to track it — a tape measure and a reliable formula get you surprisingly close.
TL;DR — Take a few measurements and enter them in the body fat calculator for an estimate using the US Navy method.
Why body fat beats weight alone
Two people at the same weight can look and function completely differently depending on how much of that weight is muscle. Tracking body fat instead of just the scale tells you whether a diet is costing you muscle, or whether training is adding it — information the scale hides.
The US Navy tape method
This method estimates body fat from a few circumference measurements: neck and waist for men, plus hips for women, along with height. It is the approach the calculator uses because it needs only a tape measure and reproduces well when you measure consistently.
How to measure properly
Accuracy comes from consistency. Measure relaxed, first thing in the morning if you can, without pulling the tape tight. Take the waist at the navel, the neck just below the larynx, and hips at the widest point. Measure the same way each time so your trend line is meaningful.
Reading the result
The percentage places you in a band from essential fat up through athletic, fit, average and high. Remember some fat is essential — going too low is unhealthy. Treat the number as a trend to watch, not a target to chase at all costs, and run it in the body fat calculator alongside your lean body mass for context.