Countertop Height: By industry standards, the standard floor-to-countertop height is 36” . If you are remodeling your kitchen and buying pre-built base cabinets (34 ½” standard), this will be the height they fit into by most manufacturers’ standards. Also, appliances are usually sized for this height (dishwashers, stove/oven combinations, etc.). The ergonomic rule-of-thumb is that your elbows should be bent at a 45-degree angle when your hands are resting on the countertop. If you try this and take your own specific measurements you’ll know the optimal counter height for your own size.
Kitchen island height – given the popularity of kitchen islands, this is one place where many people find that two different heights can be incorporated, given a customized option that doesn’t affect the entire kitchen counter surface. Bar stools (if incorporating an eat-in component for the island) would need to fit in underneath the counter, so the accepted height is usually 42” for this countertop space. But if you want an area to roll dough, for example, you may want to lower that 2”-3” from the standard 36” to make it more comfortable, thus opting for several options within this one surface area.
Breakfast bar overhang: The right amount of overhang Island seating generally comes in three heights: table (30 inches), counter (36 inches), and bar (42 inches). Each one requires a different amount of overhang (also called knee space) for diners to sit comfortably. The higher the seating, the less knee space needed, as per these recommendations from the National Kitchen and Bath Association.
Distance between seating furniture: Aim to provide between 3.5' and 10' between seating options to help conversation flow without crowding a room.
Side table and sofa height: In general, an end table should be approximately the same height as the arm of your sofa or chair. This allows guests to set down or reach for drinks without straining, and it also lends a more cohesive feel to the room.
For optimal viewing, size your TV based on its distance from the sofa. To get the minimum screen size in inches, divide the viewing distance by 3; for the maximum, divide by 1.5. Already have a TV? Use these guidelines to position your couch. Aim for a 15- to 20-degree viewing angle to the center of the screen
Area rugs and furniture: Too often area rugs end up feeling like bath mats. To keep your area rug from feeling random, at least the front two legs of a sofa or chair should rest on the rug.
Distance between room-size rugs to walls: Allow about 24" between the wall and room-size rug in a large room, and between 12"- 18" in a smaller room.
Toilets: "Comfort height" toilets, which sit about 17 to 19 inches high, or about two or three inches higher than usual have become the most common choice. The added height makes getting on and off easier, but make sure your feet can comfortably rest on the floor for ergonomically-correct use. A measurement of 12 inches is standard, but 10-in. and 14-in. models are also available. If you are remodeling, make sure the new toilet matches the existing toilet’s “rough-in” measurement—the distance from the wall to the center of the toilet flange (the hold-down bolts)
Shower head: Remember to consider that all shower users might not be the same height (adults, children and seated bathers) The temperature control should be placed about waist high, approximately 36" from the bottom of the shower enclosure. (For tub/shower systems, the temperature control will need to be placed 8"–18" directly above the tub spout.) The shower head should be installed so that it is above the head of the tallest user, but still within the reach of the shortest user. Ideally, the tallest user should not have to crouch or duck under the shower head to rinse his hair, while the shorter user should be able to manually adjust the spray modes of the shower head.
Shower Seat: The standard depth, or measurement from the back to the front of the seat, is between 15 and 16 inches, which is also the depth recommended by the Americans with Disabilities Act (ADA). The seat should be deep enough for the user to sit comfortably, but not so deep that it is difficult to rise from or that it blocks the entryway to the shower. Depth varies between seat types. For example, an L-shaped seat is often narrower than a standard rectangular one. Fold-down seats with a reduced depth are also available for shower enclosures with limited space. Some of these seats are only around 12 1/2 inches deep.