So the book Food Storage in a Nutshell will answer this for you. There's this nifty little chart that takes each item and then tells you the amount you need for 1 person, for 2 people, for 3 people and so on. And there's lot more info than that. I pretty much think it's the Bible of Food Storage. Easy peesie, lemon squeezie (that's the family quote now from Addie's 1st grade teacher).
But what you may not realize . . . did you know that the recommendations for amounts that the church used to give were the amounts that you could SURVIVE on. Not live on, but survive on.
Big difference!
So, of course you need a place to start, but make sure it's where you start and not where you end.
First things first . . . Inventory. It's not just an accounting word or just an accounting theory. You need to go look at what you have, look at the dates, and write it down. This will do 2 things: 1) Give you a place to start, and 2) maybe it will make you realize (like it did me) that you're pathetically unprepared.
I went to the cannery and dropped a whole $100 every other month . . . or was it actually once or twice a year. I thought I was staying focused on my food storage and moving along okay. We would not have lasted 1 month and no joke we would have been chewing on wheat kernels and inhaling a few horribly uncared for and thus really bad tasting cans of dried milk.
And next second suggestion . . . Involve your Husband and here's why.
1) Every time I sent Ansen to the store he came home with a huge bucket of banana chips, or 742 servings of blueberry pancake mix. I was focused and this was not on my list. BUT, he brought the variety that I wasn't thinking about. You can get food exhaustion from eating the same thing over and over so variety is good. He's also helped me fill up our 3-month with a good variety "stuff" (my nice word for mostly junk food - but we still seem to need it).
2) You need help because this is a lot of work and it requires a lot of focus. I gathered mine pretty quick so it was literally a part time job for me and I thought about it all the time. If I didn't have Ansen doing some shipping, helping me can and carrying my big boxes around I would have died (literally - I was pregnant).
3) The finances of food storage is easier when you're on the same page, you both understand the importance, and you're both working towards a family long tern goal.