If the weight of barbell bench press is 100kg, then the weight of dumbbell bench press is between 50 and 70kg. But this is only a rough estimate, and the actual conversion ratio will vary from person to person, depending on the individual's body structure, strength distribution and training habits.

This conversion method is based on the fact that dumbbell bench press requires higher grip, flexibility and balance, so its weight is usually smaller than barbell bench press. The specific needs are determined according to the individual's physique and training.