Monarch Butterflies How Many Football Fields Would the Monarchs Cover? Example: Using the population estimate of 1.19 hectares in winter 2012/2013, here is our calculation: 1 football field is roughly 1 acre. (The exact measurements of football fields vary.) 1 hectare = 2.47 acres 2.47 football fields in 1 hectare 1.19 hectares of monarchs 1.19 X 2.47 = 2.93 football fields of monarch trees this year. Just think: Monarchs flew to Mexico from across eastern North America and occupied an area smaller than 3 football fields! 1 2 3   Facebook Pinterest Twitter © 1997 – 2019 Journey North. All rights reserved.