How walking speed changes with age
Walking speed peaks in young adulthood and declines gradually from approximately age 40 onwards. Population studies estimate a decline of roughly 0.8–1.2% per year after 40, or about 0.01 mph per year. By age 70, average walking speed has typically declined by about 0.3 mph compared to a person's prime. This calculator applies a simplified version of this adjustment: pace is reduced by 0.01 mph for each year over 40, with a floor of 1.8 mph.
Fitness level interacts with age. A highly fit 65-year-old may walk at the same speed as an average 45-year-old. The four fitness levels in this calculator (low, average, good, very good) represent base pace bands of 2.5, 3.0, 3.5, and 4.0 mph respectively before age adjustment is applied.