bf%

The official/proper way to do it is to get a caliper and take certain measurements of certain areas of the body. Or, a tape measure will give you a ballpark figure. I believe for men its your waist size, wrist size and maybe chest size? Then, you put in your weight in lbs along with height. Google it for more info but thats what I know. It'll give you a rough idea.

Pretty much the only way to get an accurate reading is through a body scan. I'm not talking about one of those electronic scales either, those are terrible, they can be off by over 10% depending on your hydration level. Calipers will get you to about only about 5% accuracy. Dexascan, hydrostatic weighting, or BodPod are the true standard measurement techniques, which you can get done at a clinic for $40-$80 depending whats available to you. Even those are only accurate to about 1%.

For purposes of planning your TDEE, you really only need about 5% accuracy, unless you are on a tight timeline and want to spend less time calibrating your TDEE. Regardless of how you calculate it, it will almost always require at least a couple of weeks of calibrating to until you hit the calorie goal where you start seeing results.