You may have heard a rule-of-thumb is that it takes 1.5 to 2 acres to feed a cow calf pair for 12 months. That means we should be able to have 10 to 13 cows. Let's see how this rule-of-thumb holds up. It looks like our rule-of-thumb held up pretty good, 11 cows on 20 acres, is 1.8 acres per cow.