I've talked before about body fat percentage- it's a much more important number than your BMI. You can be at your "correct" weight and still have an abnormally high BF percentage. You can also be "overweight", and due to having a lot of muscle, be very lean.
We've also talked about how to measure this. Unfortunately, the only true ways to do so are expensive and hard to access. Those include the Dexa Scan, Bod Pod, and Underwater Weighing. Electrical impedance machines and measuring by calipers both lean toward being inconsistent and inaccurate.
I came across this method online, and thought it was interesting. It's used by the US Navy, and they say it can be quite accurate if you are careful with your measurements. Interestingly, I just tried this- and it came out within .1% of what my Omron hand-held unit said my BF was.