I have a recipe that calls for 8 large tomatoes. How many cans and what size of canned tomatoes would I need?

Figure one of those LARGE cans would hold 4 standard tomatoes. So two cans, but I'd drain off the fluid from both otherwise you're looking at altering the recipe way too much. Just use the solids. Add the liquid to soups, or a crock potted meat.

Your recipe refers to Fresh tomatoes. Canned tomatoes are already cooked. Depending on the recipe, yo may not be able to substitute one for the other

Four cans would be about right. 400 grams per can is common in the UK which is approximately 14 ozs.

You have some options:

1) Go to the store and buy 8 large tomatoes.

2) Depending on what you're making and how many servings it makes, try to cut the recipe in half so you don't need so many tomatoes.

3) Try 2 cans of tomatoes (large cans). If you don't think that is enough, add another can or two. Just wing it. Make sure you keep track how much you use so you know for next time.

They are asking for fresh ones not tinned.