When going from barbells to dumbells, how would you calculate how much weight you should use with dumbells (without mucking around by lifting various weights)?
Guess and check.
Usually DBs are less weight than barbell. But like said about guess and check.
I'd say just go ahead and pick a weight you think you can get for your rep range. If you can do more, then add more weight. Or do less weight, depending on how many reps you're hitting.
Other than that, there's really no way of saying...
usually its 1/3 weight. for example, if you can military press 150, you can probably do 50 lb dumbells. same goes for bench. that's a generalization though, everyone is different.
i think alot more comes into play other than simple equation, not saying it is not use-able. But...consider these things also,
1. When you do BB you dont use as many stabilizers
2. Are you standing? Cause you may "pop" the weight with your back/legs if so allowing for a bit more power.
3. Range of motion. DB will change it, and if you go to deep, bye bye rotator cuff.
But yes, guess n check, but be reasonable in doing so.
I think from what everyone's said it proves that it's different for everyone. I DB shoulder press 60lbs dbs and do a 125lbs barbell. A 95lbs db bench but a 205lbs barbell press.