I have 10 foot ceilings and I think our baseboard height is 7 1/4". It's a good height, any shorter and it'd look too small

Ditto Tiger Lily. We have 10 ft ceilings and 7 1/4" base, looks proportionally 'right'.

I suggest you ask your builder to make a full-scale mock up of whatever trim and details you are considering so you can make an informed choice.

If the space is a one story with a flat ceiling with no crown moulding in the northern hemisphere and the walls are lightly colored with a relatively with a smooth surface, take the ceiling height in inches and multiply it by any number between 0.0416667 and 0.0625 and that will give you the range you should be looking for.

@Mark,

Lots of folks in the northern hemisphere use the metric system. Is there a formula in metric units? What about the correction factor for paint sheen?

My baseboards for my 10' ceilings are 1 x 8's which is really 7.5" high. It's just the right height.

I also did 1 x 8 for the top of the doors and windows but my house is a craftsman style and it works for that. What is the style of your house and how will the windows be trimmed out?

"Is there a formula in metric units?"

In-depth research is currently being conducted on that factor.

June all the houses in my new development except mine are contemporary sugar cubes and all have the flat molding detail for the base like I do with no crown. It works.

Speaking of windows, any glass closer than 18" above the finished floor in most jurisdictions must be tempered. Be sure to factor in that expense into the design decisions.

The list of conditions in the IRC which require windows to be tempered can be confusing. While a less than 18" distance from the bottom edge of a window to a floor is a necessary condition, it's not sufficient by itself to require the window to be tempered. Note the use of the word "all" in the following excerpt from the 2015 IRC:

R308.4.3 Glazing in windows. Glazing in an individual fixed or operable panel that meets all of the following conditions shall be considered to be a hazardous location: 1. The exposed area of an individual pane is larger than 9 square feet (0.836 m2), 2. The bottom edge of the glazing is less than 18 inches (457 mm) above the floor, 3. The top edge of the glazing is more than 36 inches (914 mm) above the floor; and 4. One or more walking surfaces are within 36 inches (914 mm), measured horizontally and in a straight line, of the glazing.

Installation of an awning window under a fixed pane-- which the OP is considering-- should not require the windows to be tempered unless it, too, meets all of the criteria.

Are awning windows near the floor safe if you have small children or grandchildren?

this makes me uneasy.

Charles Ross Homes- Thanks so much for the extra info on the need for tempered glass. I was originally going to do a semi circle type arch at the top, which was nearly $4,000 for that window section...so the 3 rectangles will be much cheaper overall. I am still debating if I want to do the full picture window from 7.5 inches from floor to my 96inch header...or do the awning window at the bottom. If I do the picture windows, the door directly to the left will have a retractable screen. We are building in woods, so there won't really be airflow, we just want to hear nature.

ILOVERED-good point. My kiddos are older..and we would definitely babyproof for grandbabies...but there are so many other hazards that a locked window at that stage.

Thanks to everyone for the calculations...I started with Google..but big difference between 5 and 8 inches!!!

CP-Thanks for the photos. I'm thinking 1*8 for baseboard, 1*6 for above doors/windows and maybe 1*4 for the sides of my doors. I don't want anything too fancy.

JuneKnow-Interesting. I pulled out all my crown molding and put 1*4 baseboard trim in my 8ft ceiling flip house. I like the nice look of the trim, but the cleaner look on the ceiling. I use to love crown molding...but I'm getting a little simpler in my tastes as I age. Still like nice and expensive...just a lot more things in my house to focus on than some crown molding 10 ft high.