The size of Triangle Flat is approximately 145.8 square kilometres. It has 1 park covering nearly 9.8% of total area. The population of Triangle Flat in 2011 was 267 people. By 2016 the population was 58 showing a population decline of 78.3% in the area during that time. The predominant age group in Triangle Flat is 60-69 years. Households in Triangle Flat are primarily childless couples and are likely to be repaying $1400 - $1799 per month on mortgage repayments. In general, people in Triangle Flat work in a managers occupation. In 2011, 79% of the homes in Triangle Flat were owner-occupied compared with 69.5% in 2016.