Use a chart to find the average life expectancy of an area.
Search for a chart that provides an average body mass for first-time birth females. If no chart is available, ask a hospital if they would be willing to provide some data.
Plug the average life expectancy and the average body mass for first-time birth females into the equation LRE = (R / m^a) * E, where R is the adult female's age, m^a is the average body mass for first-time birth females, and E is the average adult female's lifespan. So, if a 32-year-old female in the United States has a body mass of 66 kg, and the average life expectancy of adults in the United States is 78.1, then her LRE = (32/66) x 78.1 = approximately 38. So, this woman might be able to reproduce another 38 times in her lifetime.