Ok, so my method of provisioning has three steps.

1. Create a menu and get it approved by everyone onboard

2. Create a spreadsheet with every ingredient and everything you will need to make each dish, and then sort by ingredient

3. Add up how much you will need of each item, and make a shopping list

Step One.  On my menu I included our activities for that day so that everyone could see and relate it to the meals.  For instance if we were going to be sailing all day I would include a cold lunch like Turkey sandwiches.  Here is an example:

Tuesday – Make our way around the southern end of Vieques and pick-up a
mooring at Esperanza.  For those wanting to do Biobay, this is the night
as it is the new moon.  We should be able to get dinner on shore this
night.

B- Bagel halves with butter and jam, Hard boiled eggs, Bananas

L- Turkey Sandwhiches, Pasta Salad

D- Restaurant

I also added a group snack for each day as I assumed with all the physical activity we would be needing it.  We also hae 4 teenagers aboard who require extra food. At the end I also included a very open list of possible drinks.  Without knowing exactly what everyone likes to drink though, its a hard thing to add.  I will be leaving that largely up to them at the store, with only the beer counted out at 5 beers per person per day.

Step two.  After everyone had made their changes to the menu I went through and put them on my spreadsheet.  My sheet has three columns, Dish, ingredient, and quantity.  I went through and looked up recipes for all of the meals.  On Allrecipes.com you can change the quantity of servings to avoid a lot of in your head math.  I did 2 servings per person, and for lighter dishes I did 2.5 servings. If seeing helps here it is  Provisioning List  After that I just sort by ingredient and add up all of the amounts.  I wouldn’t stress to much on what unit you’re using ie pound vs package vs can.  You are the one adding it up anyway.

Step three.  I just type it all up into an easy to read list for whomever will be doing the buying.  Here is mine Shopping List

As  side note I think it would be helpful to use your original spreadsheet (before sorting) and your menu to portion off foods on the boat for each day.  That way for example if you have rationed pasta salad for two meals, it won’t all get served at the first meal.  I would expect that whatever is served will be gone.  Also for each meal you could mark what extra food you had left over.  That way you know the difference between your leftovers and your provisions for future meals.  So if people are hungry you can offer them food without ruining your meal plan.