Variable costs are expenses that vary directly with the size of a firm's output. As output increases over the range of production, the variable costs fluctuate. Variable costs include raw materials, labor, fuel, and wear and tear on equipment. | Variable costs are expenses that vary directly with the size of a firm's output. As output increases over the range of production, the variable costs fluctuate. Variable costs include raw materials, labor, fuel, and wear and tear on equipment. |