Um.. what you can do is maybe test your barbell bench 8 rep max. Then test your db bench 8 rep max after 72 hours of barbell bench to ensure you recovered.

Now plot those 2 numbers in a ratio, barbell: dumbell and you shud get a good estimation.

Disclaimer: There is 0 scientific evidence behind this method. I came up with it myself.

From my understanding dumbbells presses are slightly tougher than Barbell as it requires more focus and stability. If I do 2 x 25 kg dumbbells presses, do you think I can bench at 70 kg for barbell? I know this very much depends on individual, just to have a rough idea on differences in weights.
I don't have access to gym yet thus my training can only work on dumbbells at home.

One is not superior to the other, both has its benefits.

As for weight, yeah, sounds about right.

Based on my experience, dumbbells press is tougher because of the setup where you need to lift it up compare to barbell which is already in place. Another thing is you'll need to stabilize the weight.

Understood. Just want a rough estimation before I start flat benching with barbell. Thanks

From my understanding dumbbells presses are slightly tougher than Barbell as it requires more focus and stability. If I do 2 x 25 kg dumbbells presses, do you think I can bench at 70 kg for barbell? I know this very much depends on individual, just to have a rough idea on weight differences.
I don't have access to gym yet thus my training can only work on dumbbells at home.

If you somehow feared of transitioning from Dumbbell Press to Barbell, fret not. Always remember that you need to do dynamic warmup for each exercises, (low weight with more reps warm up sets until you reach your intended working sets). During that dynamic warmup, you can gauge your working sets comparing it to your dumbbell weight.

From what i understand if ur using dumbbell you can get deeper stretch where as barbell requires muscle balance and if you get those muscle imbalance u should use dumbbell first.

I can db bench 30s for 5 reps with ease but I can barely do 55kg for 8 or 9 when I do it on the bar.

I guess some are just mechanically better doing with the bar while some with the DBs?

So the best way to find out is to do it slowly, especially when you haven't done it on the bar for so long, you shouldn't go straight near your max.

Bro, your DB benching is 2 x 30 kg ya? Did you include the weight of bar when flat benching? Will do it slow since I have not touch barbell for years.