Coffee tables come in many shapes, sizes, colors, and styles. So many, in fact, that it might be confusing what you should be considering or eliminating when it comes to finding the perfect one.
By far the most common questions are about table height. The short answer (no pun intended) is that coffee tables should be between 10 and 18 inches tall. Where your table should be in that range depends on several factors. Let's explore some of these:
How high is the seating around the table? A coffee table should be somewhere between 2 inches shorter than the seating and even with the seating.
Will you put your feet up on the table? A taller table can make this uncomfortable.
Do you want a lower shelf? If so, how much room do you need between the shelf and the table top?
Do you prefer to reach across for items, or are you comfortable reaching down?
How tall is other furniture in the room? The coffee table should complement the rest of the room.
The rule of thumb for coffee table length is 2/3 of the length of the closest couch. You don't need to get overly scientific and calculate out to 3 decimal points, but that general ratio will look good.
You could base the depth of a coffee table on the dimensions of the space and furniture in the room. There is nothing wrong with just finding a table that is a comfortable width give the rest of the room. In fact, if you know the length of the table, your eye will eventualy settle on a size that is pleasing to you, and that's perfect.
Interestingly, furniture and interior designers have discovered there is a typical ratio between the length and width that most people find appealing. So, if you are unsure, you can confirm your choice with a little bit of math. The ratio is: length = width x 1.62 or, conversely, width = length / 1.62. From this we can generalize some table sizes to 36x22, 48x30, 54x33, 62x38.
The last space consideration, which should probably supercede other factors, is how much walking around space you need to feel comfortable. The absolute minimum is 24 inches. Less than that and you will be bruising your shins and toes forever. 30-36 inches is better. If your room is quite large, keep the coffee table space in this range for the sides of the table that are adjacent to seating. It is always fine to leave a side or two open to the rest of the room.