The linked one asks for your height and weight, but it's not a BMI calculator.
It also asks for your neck and waist measurements. That is, for a measurement of something which is almost always all muscle and bone (the neck) and something which has some fat on it (the belly).
I don't know if it's accurate, but it does try to distinguish between fat and muscle.
I am not too fussed about body fat percentage anyway. You know if you have too much or too little... And if your weight stays the same as you get stronger, well then you are probably putting on muscle.