Fixed, Variable, Per-Use, and Overtime Costs
Microsoft Project can calculate project costs from resource rates and usage, per-use charges, and fixed task expenses. “Variable cost” is a useful general description for costs that change with work, quantity, or rate; it is not a separate built-in cost field. Knowing which cost input fits an expense helps you enter it in the right place and interpret Project’s totals.
The main cost inputs
Section titled “The main cost inputs”Resource rates vary with assigned work. A work resource’s Standard Rate applies to regular, non-overtime work. You can use cost rate tables when rates differ by task or change on an effective date. These changing amounts are often what people mean by variable costs; Project does not provide a separate field named “Variable Cost.”
Per-use costs add a set charge when a resource is used. For a work resource, the fee can be charged in addition to a rate-based cost and does not depend on how long the resource works. For a material resource, the per-use amount is charged once regardless of the quantity consumed.
Fixed costs are nonresource expenses entered directly on a task, such as a one-time travel or delivery charge. They do not require an assigned resource. For a project-wide expense such as overhead, a fixed cost can also be entered on the Project Summary Task.1
Overtime needs both a rate and overtime work
Section titled “Overtime needs both a rate and overtime work”An overtime rate sets the price for overtime work, but entering a rate alone does not classify extra hours as overtime. You must enter the overtime portion on the assignment in Overtime Work; Project then calculates that work using the resource’s overtime rate. Overtime Work is part of the assignment’s total work, not extra work added on top, and entering it may shorten a task’s duration unless the task is fixed-duration.2
Enter costs in the right fields
Section titled “Enter costs in the right fields”- Standard and per-use resource costs: In View > Resource Sheet, enter the resource’s Std. Rate and Cost/Use values. Use a rate unit such as
/hor/dwhere appropriate; if no unit is entered, Project interprets the rate as hourly. To set rates that vary by task or effective date, double-click the resource to open Resource Information, then choose Costs and use a cost rate table. - Task fixed costs: Open View > Gantt Chart, choose View > Tables > Cost, and enter the amount in Fixed Cost for the task. To include a project-wide fixed expense, show the Project Summary Task and enter it on that row.
- Overtime: In View > Resource Sheet, enter the resource’s Ovt. Rate. Then open View > Task Usage, choose View > Tables > Work, right-click the Work field, and select Insert Column > Overtime Work. Enter the overtime amount on the relevant resource assignment.
Resource-based costs are calculated after resources are assigned to tasks. Project’s cost fields can show totals for tasks, resources, assignments, or the full project; a task’s projected cost combines costs already incurred with costs still remaining.3