The Goods

It's all in the numbers: Simple design calculations to perfect your living space

Design like a pro! We share some simple math that will take your living space to the next level.

A lot of people don't realize how much math is involved when it comes to interior design. When decorating your home, you can use a little math to make sure your decor is pleasing to the eye and your living space is functional. Designer Trish Johnston stopped by the show to share some tips on how pass this numbers class with ease.

Dining room decor math


Chandeliers should be hung approximately 30-34 inches over a table with an 8 foot ceiling height. If your ceiling is higher than 8 feet, mount the chandelier an additional 3 inches higher for each foot of ceiling. And don't forget – everything must be on a dimmer! 

Dining table

When choosing a dining table, be sure to select one that will allow for essential elbow room. No one wants to be crowded next to their dining companions when eating! A general rule of thumb is that the table should be large enough for each guest to have at least a 1' on either side of them.


There needs to be at least 2 feet of space between the wall and the back of chairs when they're pulled out. Chairs can take up a lot of space – but they don't have to. Get creative with the seating in small spaces – we love ottomans. They take up less space and can be tucked right under the table when not in use to save space.


Deciding on the perfect sized rug for your dining room can be daunting. It's best to leave a 5-6 inch perimeter around a rug's edge, so that the entire room is almost completely carpeted. Another fun and practical option is to opt for an abstract shape rug like cowhide, which is really easy to clean and super durable.

Living room decor math


When selecting a rug for your living room, look for a style that spans close to 60% of the room. Unlike the dining room, be sure to leave at least 12 inches of floor space around the perimeter of the room. For a pleasing visual effect, place all of legs of the furniture on the rug, or just the two front legs. This makes the space feel grounded and super cozy.

Wall art

Choosing the right sized piece for over your sofa can be tricky. Here's a couple of rules that will make the hunt a little easier: art should never be the same width as the sofa. Instead, it should be about two-thirds as wide as the sofa. Position the art so that the middle of the piece is about 60 inches from the floor and centered. The bottom edge of the art should be roughly 6-8 inches above the sofa back. This will help you achieve the right balance in your living room. We say go big for living room art – it's a great statement and sets the tone for the room!

Throw pillows

What's the magic number? Deck out a standard seven-foot sofa with three 20-inch-square pillows. Try a different pattern for each to add contrast and texture. Put two on one side and one on the other – an odd number is always more visually pleasing to the eye!


Always opt for lighting that is warm, textured and super ambient for your living space – this will make it seem inviting and relaxing. Center your fixture over the middle of the furniture plan to please the eye. Remember that there should always be a minimum of 6'5" under the ceiling fixture!

Accent tables

When shopping for a coffee table, go for one that is about two-thirds as wide as the sofa and a couple of inches lower than the seats (typically 14 to 16 inches high). Not only will this coordinate well, it will be at a comfortable height for those sitting on the sofa. And don't place the table too close to the sofa – you should leave roughly 18 inches between the table and seats so that people can walk by. For side tables, select ones that are the same height or a few inches shorter than the sofa arms.

Resource guide


Farrow & Ball

Tonic Living