Cost Calculator AI
Construction & ContractorsCost-Plus CM Model

General Contractor Fee Calculator

Calculate Cost-Plus general contractor management fees (10%-20%), superintendent site supervision, and builders risk insurance.

Calculation Results

Cost-Plus Contractor Fee Formula

Turnkey Total = Direct Hard Costs + (Hard Costs × GC Fee %) + (Months × Superintendent Fee) + Insurance
  • GC Fee: Typically 10% to 15% on large commercial projects, 15% to 20% on custom residential homes.
  • Superintendent Fee: Dedicated on-site supervisor charged as a monthly general conditions fee ($3,000–$5,000/mo).
  • Builder’s Risk Insurance: Specialized coverage protecting the structure against fire, wind, and theft during construction.

Step-by-Step Worked Example

Scenario: A $300,000 custom home build taking 7 months with a 15% GC fee and $4,000/mo supervision

Calculation Steps:

  1. GC Percentage Fee = $300,000 × 0.15 = $45,000
  2. Superintendent Supervision = 7 months × $4,000 = $28,000
  3. Builder Risk & Permits = $3,500
  4. Total GC Fees & Conditions = $45,000 + $28,000 + $3,500 = $76,500
  5. Turnkey Cost to Owner = $300,000 + $76,500 = $376,500
  6. Effective Fee Percentage = ($76,500 / $300,000) × 100 = 25.5%
Result: The GC management fee is $45,000 plus $31,500 in supervision and insurance, bringing total owner cost to $376,500.

How to Use This Calculator

  1. 1Enter total direct subcontractor and material hard costs.
  2. 2Select GC fee percentage and estimated project duration in months.

Assumptions & Limitations

  • Estimates are based on standard national averages and current prevailing construction materials and contractor rates.
  • Actual trade bids may fluctuate according to local building code requirements, permit fees, and site topography.
  • Always obtain multiple written bids from licensed, bonded, and insured contractors before commencing work.

Frequently Asked Questions

What is the difference between fixed-price and cost-plus contracts?

In fixed-price (lump-sum) contracts, the builder takes the risk of cost overruns and keeps any savings. In cost-plus contracts, the owner pays exact trade invoices plus an agreed-upon percentage fee, with complete open-book transparency.

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