Road bike gearing

[Stupeo]

So, I'm a fairly novice road cyclist and have a Ribble R782 with Ultegra Di2 that I bought a few months back.

The bike has a 11-25 cassette and 39/53 chainset. The bike is very fast on the flat, but I really do struggle on some hills. My old Carrera with just 14 gears felt much easier climbing.

I'm trying to find a good resource to understand the gearing, as I suspect I need a different cassette.

Can anyone help or any suggestions?

Thanks.

[Stupeo]

Thanks all - appreciate the advice.

I've downloaded the Gear Calc app and will have a play.

Reading the advice and watching the GCN gearing video I am inclined to try a new cassette (11-28) first to see if that helps. I don't want to spend a fortune...already upset the missus with the subsequent Garmin 520 and GP 4 Season purchases close to Christmas