Objective To determine how well the Mini Nutritional Assessment (MNA) Short Form (MNA‐SF) performed as a nutritional screening tool when calf circumference replaced body mass index (BMI) as the included anthropometric measurement. Methods A total of 100 patients ≥70 years were recruited from a Geriatric Evaluation and Management Unit. Results Mean age of patients was 85.2 (6.1) years. By the full MNA, 40% of patients were malnourished. The MNA correlated highly with both of its short‐form versions (r = 0.87 and r = 0.90 for the BMI and calf circumference versions, respectively). Both MNA‐SF versions also showed high accuracy in identifying malnutrition (auROC values >0.89). Conclusions The MNA‐SF is a rapid and accurate way to screen for malnutrition in hospitalised older adults. Substitution of BMI measurement with the time‐efficient calf circumference measurement maintained MNA‐SF accuracy. It is recommended that calf circumference measurement be used for nutritional screening by MNA‐SF in a hospital setting.