The size of Dee Why is approximately 3.4 square kilometres. It has 13 parks covering nearly 12.2% of total area. The population of Dee Why in 2011 was 19,838 people. By 2016 the population was 21,524 showing a population growth of 8.5% in the area during that time.
The predominant age group in Dee Why is 30-39 years. Households in Dee Why are primarily childless couples and are likely to be repaying $1800 - $2399 per month on mortgage repayments.
In general, people in Dee Why work in a professional occupation. In 2011, 54.3% of the homes in Dee Why were owner-occupied compared with 50.3% in 2016.