It depends on what you want to use it for, but 850 sq. ft. is already a big pool

How about you you lay the 850 sqft pool in your yard and see if you think it's big enough. If you don't think so, go bigger.

My PB originally drew up my pool at around 400 sqft. I redrew it to about 650 sqft because the original had so little shallow end (that diving template can eat up a LOT of pool). Still to me it looked kinda small.

We drew it out on the yard last week to make sure it would not come too close to existing trees. It feels a whole lot bigger on the ground than it does on paper. I just gotta remember that it's 1' smaller all the way around (we drew the hole). Perhaps I want to make the pool 1' bigger all around ;). That's the same thing I think about all the rooms in my house too...

Thanks. We did spray paint it out in the yard but it is still so hard to tell. My guess is the size of the pool is fine it's just the size of the yard makes everything seem much smaller. We will have 24' of shallow end and about 24' of deep end which seems like enough space. I just don't want to have it finished and say "I wish we had made it bigger" I think I am just stressing out about the whole thing and getting it right.

Your pool is plenty big. Ours is 10 x 20 and we have just as much fun, plenty big to swim laps, play voley ball and still have a lot of people in it. Here is pic with some of our closest friends; kids ages from 3 - 65 years, lol Please note that is still lots of room in the pool for more people.

Playing volley ball with no net. It still works as you can see.

Here is a link that might be useful: Our pool build in Jacksonville