Draw out the furniture you want on the deck to scale in the arrangement you would want it, draw a rectangle around that, measure the rectangle, and there you go.

Ditto what Mark said for the inside of the house as well. For example, if you try to put a table in your little bump out for a breakfast area, it will impede with space for stools at the island. You might find that flattening that bump out to a straight wall with windows or sliders (or a combination) gives you more flexibility for kitchen and furniture layout. Laying out your space and furniture - inside and out - will help.

You might also want to vet your kitchen in the kitchen forum.

So many factors need consideration. Agree however that a patio is less maintainance long-term and with a pool likely will unify the backyard while offering additional privacy.

Size - think dining, social and intimate spaces. Ours is 26x24 with an additional 8x12 where once a hot tub resided. As a previous poster recommended, draw to scale with furniture.

Here’s a look at ours for review:

https://youtu.be/H5t9G-Gujqw

A 12'X20' deck may be a little too small if you want seating for 6-8 people at a table, plus a grille, all on the same deck, especially since your entry/exit to the house is in the center of the deck (as shown on the plan. You need to figure on space for grilling, space for a table and chairs and circulation space. Might work better if you rotated the deck 90-degrees, or made it larger in the configuration shown.

Plan for stairs, current or future.

I love decks - but I would rather have a patio next to a pool.

That said - the deck at our last house was 10'x20', with patio door and stairs on the same end. It was cozy for a small round table and 4 chairs, and a grill. 2' wider would have allowed for a slightly bigger table, but not much additional seating.

In our current house, I'm planning a 15'x15' deck, with a swing incorporated into one side, instead of railing in that location. During the planning, I taped out 15x15 on the basement floor, and placed our outdoor furniture in the square (which is what convinced me I needed to put the swing at the side).

@AnnKH - you might want to create your deck 16x16 because lumber comes in even foot lengths. For only a few additional deck boards you’ll obtain about 30 sq ft at the same materials cost.

Unfortunately, there are trees preventing me from going any bigger. Even 15x15 is going to require some tree trimming to fit.

I would get the pool built first. it's going to cost a lot more than the deck and is more important IMO. Better to compromise on the deck because of the pool you decide on instead of the other way around. I agree with the above post on 16' sections. Anything over 16' will require 2 boards or very expensive lumber.

Thank you all for the comments and suggestions!

@Sara B - one matter to consider and it further suggests installing the pool first. Backfill from the home build requires several seasons to settle. Posts or patio within the exchavation will shift while the settling is underway.

Definitely, 20X16 is a nice size deck if there is no size restriction for these dimensions. Did one a few years back and homeowners love it, originally they planned to do 14' out I talked them out of it, and they said that after the deck was completed, they visited a co-worker's house with a 14' out deck and they sad it felt a bit small, that extra 2' makes a big difference and plenty of room for a nice gathering... also if needed there is room to put a built-in bench.

Our deck is 24x10 and we have a sectional and coffee table, table for six, and a grill out there and it works great. All fits perfect. Can you share more about the site and what you mean by deck vs porch vs patio? I think language matters and sometimes terms are used interchangeably but mean different things.