Many enterprises publish both financial and non-financial information, with the rapid increase in sustainability reports and integrated reports published today. Information users investing in a more conscious manner can investigate the sustainability of businesses and demand both past and future financial and non-financial information. In addition, as a result of increasing environmental pollution, sustainable use of the biosphere, environmental policies and environmental information of enterprises become more questionable. Enterprises pay more attention to environmental information within the scope of environmental accounting. Accordingly, the publication of estimated future data on environmental information, which is an important part of non-financial information, may be a requirement in the near future. Therefore, the purpose of this study is to investigate the usability of the Gray Estimation Method to determine the environmental sustainability of the enterprises. For this purpose, the environmental information published by a firm in its sustainability reports has been taken into consideration and the forecasted environmental information of the company has been reached by applying Gray estimation methods. As a result of the study, it was found that Gray estimation methods provide very reliable results with low relative error percentages. Therefore, thanks to the use of estimation methods, it can be seen that future forecasts can be included in the reports as well as environmental data realized in the sustainability reports issued by enterprises.