I have a hybrid, and I'm thinking about getting a road bike. I'm new to cycling, and not the strongest climber, so I'm a bit nervous about going from a triple to a compact, and what to ride in a similar ratio as my lowest gear would be to see how I can handle some steep hills.

My current bike has a 48x38x28 crank.

The rear cassette is 12x32 (8 speed). I believe it is 12,14,16,18,21,24,28,32.

Which possible combination of the gears would best simulate the lowest gear on a new road bike (34x28). If I can handle the equivalent gear on steep hills on my trek, then I'll know I'll be ok with a double on a new bike. The Trek has 700x35 c tires, the road bike will be 700x23 or 25.

What you want to do is calculate "gear inches".

All things being equal, the road bike with 23c tires running in 34x28 is 31.89 gear inches

The trek with 35c wheels running in 28x24 is 31.70 gear inches. Pretty similar.

...unless my math is off in which case I apologize in advance. I used this site:

https://cycleseven.org/bicycle-gear-inch-calculator

edit: Just to be clear, though, this only accounts for one factor on how different bikes will feel when climbing hills. Don't forget to account for crank-arm length, bike geometry, handlebars, bike's weight, etc. All those good things.

Thanks for the quick response. That news is better than I would have guessed. I imagined loosing a lot more gear inches than that, so I think 34x28 is manageable. I haven't even started to test ride bikes, so I may end up with a triple, but a double seems feasible.

Yeah, no problem. In my own riding, hand position has an enormous impact in how hills feel to me, and the hand position provided by riding in the drops or on the hoods of a road bike makes climbing so much easier than the standard hand position with flat bars. I feel like, subjectively, just repositioning my hands is the same as going down a couple gears, so that's something to consider as well.

Don't shy away from a triple for the sake of appearance or geekitude or whatever causes people to do that. I rode with doubles for years, but a friend moved to the Caribbean and left me an old Trek tourer with a triple. I hated it for about a day, but I live in big mountains and after a few weeks I converted one of my other rides, too. If you don't need the granny, you don't have to use it, but it's sure nice to have when you do. And you can pretty much ignore claims that it screws up the shifting. Anybody who can't shift the front derailleur should probably buy a car.

I'm not worried about a triple, but it seems like a lot of good options are only available in a double, so I don't want to rule them out for that reason alone. At least on paper, the cannondale synapse is the leading contender, and it is available in a triple, which I would probably get. I'm 6'3, and overweight, but even when I hit my goal weight, I'll still be 180+, so I don't really care about saving a few grams.