The article presents the importance of farm income, taking the farm’s ability to develop into account. It has been demonstrated that achieving farm income at a parity level is insufficient to determine the farm’s ability to develop. These requirements are also not met by labour income. What informs about a farm’s development ability is the ratio of farm income to conventional costs of own production factors: labour, land and capital in the form of the competitiveness index (Wk). Its value from 1 to 1.9 points to a competitive capacity and when it reaches 2 and more, it points to full competitiveness. Based on the data from farms covered by FADN monitoring in 2017, it was found that the farm area specialising in field crops and the cultivation of cereals, oilseeds and protein crops for seeds and being able to compete (to develop) was about 40 ha of utilised agricultural area (UAA), while in the case of fully competitive farms it was 106 ha. The size of farms specialising in vegetable and permanent (fruit-growing) crops and able to compete was 7 and 13 ha of UAA, respectively. The size of dairy farms able to compete was about 25 ha of UAA and 21 cows, while the size of fully competitive farms – 75 ha and 54 cows. The size of pig farms able to compete was about 25 ha of UAA and 26 sows, while the size of fully competitive farms – 40 ha of UAA and 37 sows. The size of “mixed” farms able to compete was 39 ha of UAA and, on average, 4 cows and 7 sows, while the size of fully competitive farms – 79 ha of UAA, 8 cows and 11 sows.