Find body fat percentage for men, from BMI and age.
The Deurenberg equation, using the male-specific constant.
Men: 1.2 × BMI + 0.23 × age − 16.2
How accurate is this compared to a real body fat test?
It is an estimate based on large groups of people, not a direct measurement of you. Methods like DEXA scans or skinfold callipers give a more accurate result for you personally.