Four common types of cost estimates are: (1) Planning estimate: a rough approximation of cost within a reasonable range of values, prepared for information purposes only. Also called ball park estimate. (2) Budget estimate: an approximation based on well-defined (but preliminary) cost data and established ground rules. (3) Firm estimate: a figure based on cost data sound enough for entering into a binding contract. (4) Not-to-exceed /Not-less-than estimate: the maximum or minimum amount required to accomplish a given task, based on a firm cost estimate.