Our plan is to develop a simple, cheap and safe tool to estimate the body size and weight of dairy cows analysed from photographs taken with smartphones. This tool would directly contribute to increased competitiveness, good working environment and animal welfare in dairy production. It will also contribute to more sustainable dairy production by reducing the development towards larger, less feed efficient and promote more climate-friendly cows. During the development of the algorithm that will estimate the body size and weight of dairy cows, we will use neural networks, image analysis and photographs taken both by researchers and by the farmers themselves. The tool would have a vast potential to support breeding for more sustainable cows and regular follow-ups for efficient use of feed and management interventions. This digital and easily accessible solution will strengthen the competitiveness of dairy farms and the dialogue between farmer and advisors concerning individual cows.