Proper proportion is an essential part of good design. (Courtesy of Cheryll Gillespie)

Math was never my favourite subject in school. In fact, I still have nightmares about physics and calculus exams. Perhaps it’s because my sister, the math whiz, is hanging out with me in China this week. While I’m here I’ve kept busy reviewing house plans and it has given me lots of time to reflect on good design principles.

Yesterday, we had a walk through for a group of luxury apartment show homes that I was involved in designing and I was struck by how important proportion was - everything from handrails to fireplace designs.

I had taught the Chinese design team all about the two-thirds rule several years back when I was working on my first project in Shanghai and now I have everyone trained to look for correct proportions.

Basic math is the key to good design, without proper proportion the room will never feel or look right. The good news is that for the most part you only need to remember one measurement: two-thirds.

This one fraction will bring any room together. From drapery, to the size of a fireplace mantel , to the amount of furniture in a room and right down to the amount of accessories on a tabletop – abide by the rule of thirds.

For example, the drapery panels on the side of the window should be one-third the width of the window. A fireplace and mantel should be about one-third the size of a wall. The painting or mirror that you hang above the fireplace or the back of the sofa should be approximately two-thirds the width of the mantel or the sofa.

In general, your furniture should occupy two thirds of the floor space leaving one third of the room vacant for easy traffic flow. If you are wondering what size your coffee table should be in relation to your sofa, you guessed correctly if you said approximately two-thirds the width.

You can break the two thirds rule down further to include flower arrangements as well. For example, a vase should be one third the height of the total height of the arrangement.

Of course this is just a general guide line but it works and helps prevent the “why doesn’t this work” syndrome. To help establish this guideline in your decorating mind, flip through your favourite decor magazine and start to do the math. Take a successful room setting and note all the thirds in use. Happy calculating!