how many calories does an elderly 120 lbs women need to stay healthy?

Assuming she is relatively sedentary, a quick ballpark calculation is to take her weight and multiply by 13 which equals 1560 calories/day. While older adults don't need as many calories as younger people, they require as many if not more nutrients as some absorption levels decline with age. In other words, older adults need to make their calories count by consuming nutrient-rich, but easy-to-digest meals.