The size of Semaphore is approximately 1.2 square kilometres. It has 2 parks covering nearly 10.9% of total area. The population of Semaphore in 2011 was 2,825 people. By 2016 the population was 2,779 showing a population decline of 1.6% in the area during that time. The predominant age group in Semaphore is 50-59 years. Households in Semaphore are primarily couples with children and are likely to be repaying $1800 - $2399 per month on mortgage repayments. In general, people in Semaphore work in a professional occupation. In 2011, 65.4% of the homes in Semaphore were owner-occupied compared with 67.3% in 2016. Currently the median sales price of houses in the area is $770,500.