Hi. I am wondering if that misleading and outdated +4 "rule" is what is throwing off the measurements. Following that ridiculous nonsense, you would be concave. And that is not the case. In my experience, if a website is telling you to add four, drop it and move on.
I thought for the longest time that the hooks in the back of bras were used to accommodate smaller rib cages. Not at all. Silly me, that's why they have smaller band numbers. They are made this way so that you can get the right fit even as it stretches out over time. Apologies if you already know this.
Trustworthy websites shouldn't have that much differentiation in the results. And even then, those online calculators are only so accurate. They are good for narrowing it down if you are having trouble with the calculations. But in my experience, it is hard to know for sure until you try one on to check the fit and adjust accordingly (nevermind the fact that not all bras in the same size are made exactly the same).
Given the numbers you listed in the earlier post, I would
estimate that you are much closer to a 28C, since it is best to round down if possible. And your pictures suggest it as well. You could round up to 30B too. Experiment with both if you can. If that sounds at all odd or intimidating (and I've been there), wearing the right bra size can make a ton of difference. If you've been wearing the wrong size and switch to one that fits properly, and remember to "scoop and swoop", your breast tissue will most likely migrate. You may even look a lot bigger than before. Not to mention you'll want something to support all the NB growth.
There is a chance that you may prefer a 32 band for comfort, since it is different from what you're used to, but I would suggest the ones closer to your actual measurements first. I doubt 34 is doing you any favors, to be honest. Again, all of this is to give you a starting point. The websites should help with that too. Guidelines rather than rules.
Sorry for rambling. Best of luck!