Technical Abstract: We modeled two farms that differed in size, grazing management, and feeding strategy to determine the economic value of accurate forage measurement on pasture. We first modeled the optimal management and performance conditions for each farm with the assumption that forage on pasture was measured accurately and budgeted optimally. We also established an economically optimum balance of pasture utilization and harvest of excess forage. For Farm A, we then modeled a 10 or 20% underestimate in forage production for each month and a 10 or 20% overestimate. For Farm B we modeled a 10 or 20% underestimate of forage production on pasture and an allocation of 10 or 20% more forage from pasture when formulating the ration than was actually available. All simulations with pasture measurement errors resulted in lower farm profits (i.e., net returns) compared with a farm managed optimally. Assuming a producer would spend about 1 hour per day measuring forage yield before and after moving cows, then the labor cost (at $8 per hour) for monitoring pasture yield would be $1440 (180 days x 1 hour/day x $8 per hour). Except for one instance in our study, the reduction in net return was less than $1000 per year for error levels of 10%. Thus, a 10% error rate in measuring pasture yield appears acceptable. As the error level increased above 10%, the loss in profit was greater than the labor cost required to regularly monitor pasture yields.