Guide

How to Calculate Construction Project Cost

Total project cost is direct costs (materials, labor, subcontractors, equipment) plus an allocated share of overhead and a contingency buffer for the unknowns every project has.

Building total project cost, step by step

List every direct cost category. Materials, labor, subcontractors, and equipment — the costs tied straight to the physical work.
Price each category from your BOQ. Use your Bill of Quantities (quantity × unit rate per line) to get an accurate direct cost, not a rough guess.
Add overhead. Allocate a share of company running costs — usually 5–15% of direct cost, higher for smaller firms with less volume to spread costs across.
Add contingency. Add a buffer (typically 3–10% of direct cost) for price changes, minor rework, and delays. Higher-risk or longer projects need a larger buffer.
Sum it all for total project cost. Total Project Cost = Direct Cost + Overhead + Contingency. This is the cost base you price your quotation from.

Worked example

Materials $180,000, labor $95,000, subcontractors $70,000, equipment $15,000 — direct cost $360,000. Adding 12% overhead ($43,200) and 6% contingency ($21,600) gives a total project cost of $424,800.

Frequently asked questions

What is the difference between estimated cost and actual cost?

Estimated cost is your pre-project calculation. Actual cost is what you really spend as the project runs. Tracking the gap between them, line by line, is how you catch overruns early instead of at project close.

Should contingency always be fully spent?

No. Contingency is a buffer, not a guaranteed spend. Unused contingency at close can be recognized as additional profit — but budgeting as if you will not need it at all understates real project risk.

How detailed should my cost categories be?

For a quick estimate, four to six categories are enough. For a real project, break costs down to BOQ line-item level so you can track actual vs. planned cost precisely, not just in aggregate.