To create a tool for estimating the survival of gastric cancer patients developing MESCC, clinical factors were evaluated in 29 patients. Factors were age, gender, performance status, affected vertebrae, ambulatory status, further bone metastases, visceral metastases, time from gastric cancer diagnosis until MESCC and rapidity of developing weakness of legs. On multivariate analyses, visceral metastases (risk ratio: 6.80; p = 0.003) and rapidity of weakening of legs (risk ratio: 2.73; p = 0.023) had a significant effect on survival and were included in the tool. Scoring points for each of the two factors were either 0 or 1, depending on the 6-month survival rates. According to the sum of the points, three groups were built: 0 points (n = 12), 1 point (n = 10) and 2 points (n = 7). Six-month survival rates were 0, 20 and 100 % (p < 0.001). This tool for patients with MESCC from gastric cancer estimates survival probabilities, which is important for tailoring treatment to patients’ needs.