It's often suggested in order to see if a dishwasher will work that you bring your dishes, etc. in and load them in several models. I think the same thing, although with more shopping bags of stuff, would be your best course here to test some refrigerators. A cooler for the frozen things. It'll take you a while but you end up knowing a lot more than any other way. And you get to clean out the frig.

How many people will be using the fridge?

We are a family a five and I can tell you trying to translate cubic feet into what would actually work was a nightmare. In the end, we went with a 36" Miele integrated Fridge (freezer on the bottom) and didn't look back. We absolutely love it, the specs might have less cubic feet then other non integrated fridges but it's all usable space. Turned out to be a great purchase and we never feel cramped for space.

Love the Miele fridges! I am looking at their 30" column. I can get the floor model for about $1200 off...need to talk to my kitchen designer, but I'm thinking it's going to be mine!

I have 30" Miele columns. I can get a LOT of food in the all fridge. I just made two MASSIVE lasagnas in stoneware pans with giant handles, so had to clear out a bunch of jars of this and that into the bottom drawer (which usually has meat and eggs) and my prep area fridge drawers (which are too small for the integrated pan handles!), so the made up pans could be refrigerated overnight and cooked in the morning, but most of those jars are things like jam, chocolate sauce, and nut pastes (many more than most people have), so could have sat out overnight if need be. There was still room next to the lasagna pans for some larger jars. The other shelves and drawers all had plenty of room for the regular food for the week, extra eggs, milk and cream for ice cream making, several half gallons of juice cooling for punch, a couple of big bags of kale for the salad, etc. I can't compare it to another fridge, but it really does hold a lot.

If you want to check capacity compared to your current fridge you don't need to take heavy, perishable and delicate food to the store. Look closely at what you have that's hard to store. Look at the quantity of easy to store items. Grab a bunch of clean empty containers, jars, bottles, cans, balls, pillows, etc., that are similar sizes to your groceries, and approximate the sizes. Like one throw pillow can stand in for a foot wide drawer of produce. You can take those to the store in a few big bags, and play to your heart's content. Focus on the hard to place items, like if you buy gallon jugs of stuff (maybe good to take empties of the exact ones you favor), or giant watermelons (a rolled up bed pillow?), or baskets of strawberries. You don't have to take enough stuff to represent your fridge when full, just the normal stuff, so that you can see how much room is left.

Really, just take to the store a couple rinsed-out half-gallon milk containers, a baking pan, and a big loaf of bread. That will be enough for you to tell. People bring that to appliance stores all the time - hey, a fridge is a big ticket item. The lists above of things to bring are overkill.

You may be right, but I've dealt with too many people who couldn't imagine or project and bringing a whole lot of stuff and seeing how easily it fits is a real worry ender. :)