The size of Gillenbah is approximately 292.9 square kilometres. It has 3 parks covering nearly 10.3% of total area. The population of Gillenbah in 2011 was 405 people. By 2016 the population was 132 showing a population decline of 67.4% in the area during that time. The predominant age group in Gillenbah is 50-59 years. Households in Gillenbah are primarily childless couples and are likely to be repaying under $300 per month on mortgage repayments. In general, people in Gillenbah work in a managers occupation. In 2011, 66.9% of the homes in Gillenbah were owner-occupied compared with 63.2% in 2016.