Activity Cost Driver

What Is an Activity Cost Driver?

An activity cost driver is a measure of how much work an activity-based costing activity actually requires. It counts something, such as machine hours, purchase orders, or product setups, that shows which products, services, or customers cause an indirect cost to be incurred. Each driver links a group of indirect costs to the cost object that uses them.

Cost drivers are central to activity-based costing (ABC), a method that traces overhead more precisely than a single plantwide rate. Traditional costing often spreads overhead using direct labor hours or machine hours. ABC instead groups overhead into activity cost pools, such as receiving, inspection, or machine setup, and assigns each pool using a driver that reflects what truly causes the cost.

How It Works

The process has three steps. First, related indirect costs are gathered into an activity cost pool. Second, a driver that tracks the cost closely is chosen, and the total pool is divided by total driver volume to produce a rate:

Activity cost driver rate = Total activity cost ÷ Total driver units

Third, each product or customer is charged the rate multiplied by the number of driver units it consumed.

Example

Consider a hypothetical factory that spends 60,000 on machine setups during the year and performs 300 setups in total. The setup cost driver rate is 200 per setup. A product line that required 40 setups would be assigned 8,000 of setup cost, while a product that required only 5 setups would be assigned 1,000. The high-setup product absorbs more overhead than a simple volume-based method would suggest.

Advantages and Limitations

A good driver has a clear cause-and-effect link with the cost it assigns. This can reveal that low-volume or complex products consume more resources than their size implies. However, ABC requires more data collection and analysis, and a poorly chosen driver can distort results. Drivers are typically selected through judgment and tested against actual usage patterns.