That really isn't that much weight- imagine bench pressing 60 kilos.
A more general rule is Bench Press = 3 x 1 dumbbell weight. Pressing dumbbells is harder because it involves more balancing, so it is harder to press 30kg dumbbells than one 60 kg bar.
A more general rule is Bench Press = 3 x 1 dumbbell weight. Pressing dumbbells is harder because it involves more balancing, so it is harder to press 30kg dumbbells than one 60 kg bar.