A Guaranteed Maximum Price (GMP) contract is a type of construction contract that sets the highest amount an owner will pay for a project. The contractor is paid for the actual construction costs plus an agreed fee, but the total cost cannot go above the maximum price unless the owner approves changes to the project.

If the project costs less than the agreed maximum, the owner usually keeps the savings or shares them with the contractor. If the project costs more than the maximum price for the original scope of work, the contractor is generally responsible for paying the extra cost instead of the owner.

GMP contracts are used across virtually every large-project sector: commercial building projects (offices, mixed-use towers, hotels), infrastructure projects (seawalls, water/wastewater, transportation), industrial and manufacturing plants, healthcare facilities, higher education and K-12, data centers, and renewable-energy projects. They are especially favored where the owner wants cost certainty but also wants the contractor's expertise during design.

Owners choose GMP over a pure lump-sum (stipulated-sum) contract because GMP delivers open-book cost transparency and shared savings while still capping exposure. They choose it over a pure cost-plus contract because a bare cost-plus arrangement has no ceiling and the owner funds whatever the project ends up costing. GMP is best understood as the middle ground: the transparency and flexibility of cost-plus, plus the budget protection of a maximum price.

What Is a GMP Contract?

A GMP contract's basis of payment, in AIA's own words, is "the Cost of the Work Plus a Fee with a Guaranteed Maximum Price." The contractor is reimbursed for documented actual costs plus a fee, subject to a not-to-exceed ceiling. It is called "Guaranteed Maximum Price" because the contractor guarantees the price will not exceed the stated maximum - costs above the cap are the contractor's responsibility, which shrinks its profit on the job.

How Does a GMP Contract Work (The GMP Process)

The GMP is not a single number pulled out of the air; it is the product of a structured preconstruction process:

1. Preconstruction phase: The contractor/CM is engaged early (often at the same time as the architect) to provide constructability review, budgeting, value engineering, and scheduling input while design is still evolving.

2. Cost estimating: As design matures from schematic design (order-of-magnitude) through design development (quantity takeoffs and subcontractor budget pricing), the estimate is progressively refined and aligned to the owner's budget.

3. Open-book pricing: All subcontractor bids, material quotes, general conditions, and markups are disclosed to the owner. This transparency is a defining feature of GMP/CMAR and distinguishes it from opaque lump-sum bids.

4. Establishing the GMP: When design reaches sufficient completeness (commonly 60-90% of construction documents), the contractor issues a formal GMP proposal listing the GMP amount, the basis documents (drawings, specifications, assumptions, and clarifications), the schedule, the fee, and contingency. The owner may accept, reject, or negotiate it.

5. Construction phase: Upon owner acceptance memorialized in a GMP Amendment (e.g., AIA A133 Exhibit A), the contractor becomes contractually bound to complete the work at or below the GMP and transitions from adviser to constructor/general contractor.

6. Final reconciliation / true-up: At completion, the actual documented Cost of the Work is reconciled against the GMP. If actual cost is below the GMP, the difference is savings, distributed per the contract (e.g., 100% to owner, or a split such as 75/25). Reconciliation is based on a full audit trail, not summary numbers.

What's Included in a GMP Contract

Cost components (typical current U.S. market ranges):

• Direct costs (Cost of the Work): labor, materials, equipment, and subcontractor payments, the actual cost of building.

• General conditions: the CM's indirect project costs (site supervision, project management staff, temporary facilities, equipment, insurance, and project overhead) itemized separately from trade costs and fees.

• Contractor's fee: overhead and profit, expressed as a fixed dollar amount or percentage; roughly 3-8% is common on commercial GMP work, varying by market and risk. (A 5% fee often translates to only ~1.5-2% net profit after G&A.)

• Contractor/CM contingency: owned by the CM to cover buyout gaps, scope gaps, productivity shortfalls, and subcontractor issues; typically 2-5% of construction cost.

• Owner's contingency: held by the owner for scope additions, design changes, and unforeseen conditions; typically 5-10% of construction cost.

• Allowances: dollar figures carried in the GMP for scope items not yet fully designed (e.g., a finish package), trued up as selections are made.

Key documents:

• GMP Schedule: the construction schedule and completion dates that form part of the amendment.

• GMP Proposal: the contractor's submission of the maximum price with supporting assumptions.

• GMP Amendment: the executed instrument (e.g., A133 Exhibit A, ConsensusDocs 500.1) that sets the GMP and converts the agreement into a binding maximum-price commitment.

• GMP Payment Schedule: the schedule of values and progress-payment mechanics tied to milestones or monthly applications.

• GMP Liability provisions: the clauses making the contractor responsible for costs exceeding the GMP (absent an approved change).

GMP Set of Drawings

A "GMP set of drawings" is the specific package of design documents (drawings, specifications, assumptions, and clarifications) on which the guaranteed maximum price is based and against which future changes are measured. Its purpose is to define exactly what scope the GMP covers so both parties can later distinguish "reasonably inferable" work (included) from genuine scope additions (change orders).

Typical design completion at GMP-setting is 60-90% of construction documents in private work and some contractors set it as early as 60-75% to enable fast-track early work packages. On U.S. federal projects, the estimated cost of the work generally cannot be established earlier than 75% of construction documents and should be set before 100%.

The relationship between drawing completeness and pricing accuracy is direct: the less complete the design, the greater the contractor's risk, which is priced into larger contingencies. Setting the GMP on incomplete drawings is a feature (it enables schedule compression) but also the single biggest source of GMP disputes, because owners often perceive the GMP as a firm fixed price while contractors view it as a conditional number grounded in assumptions.

Cost-Plus Contract With GMP

A "Cost-Plus GMP" contract is a cost-plus-fee arrangement with a not-to-exceed ceiling bolted on. The owner reimburses actual costs plus the contractor's fee, but total cost is capped at the GMP. This is exactly the structure of AIA A102 and A133.

Contractor fee structures include: percentage of cost (a set markup on total cost), fixed fee (a flat dollar amount), incentive fee (bonus for hitting cost/schedule targets), and award fee (discretionary bonus for exceeding expectations).

Shared savings / incentive arrangements: if final cost is below the GMP, the underrun is split per a predetermined ratio, commonly ranging from 50/50 to 75/25, often favoring the owner creating a direct incentive for the contractor to find efficiencies.

Risk allocation: the owner carries the risk of scope/design changes; the contractor carries the risk of execution errors and cost overruns within the defined scope. The GMP cap is what makes cost-plus palatable to private owners.

What does "Cost-Plus 6%" mean? 

It means the contractor is reimbursed for the actual cost of the work plus a fee equal to 6% of that cost as overhead and profit. In cost-plus-percentage arrangements, fees commonly range from 5% to 25% depending on project size and industry. A pure cost-plus-percentage fee (without a GMP) favors the contractor, because a larger project cost yields a larger fee, which is precisely why owners add a GMP cap.

GMP vs Lump Sum Contract

A lump-sum (stipulated-sum) contract fixes a single price for a defined scope regardless of the contractor's actual costs (AIA A101–2017). The contractor keeps the difference if costs run low and eats the difference if they run high, and its internal markup and contingency are opaque. A GMP reimburses actual open-book costs up to a cap and typically shares savings.

GMP vs "Stipulated Sum": "Stipulated sum" is simply the formal AIA term for lump sum. The distinction from GMP is the same as above: a stipulated sum is a fixed price with no cost reimbursement or open-book savings mechanism.

GMP vs Cost-Plus Contract

Biggest risks/disadvantages of cost-plus contracts: open-ended final cost, weaker owner cost control, incentive misalignment under percentage-of-cost fees (higher spend = higher fee), and heavy documentation/audit burden to verify reimbursable costs.

Cost-Plus vs Fixed-Price: in cost-plus the owner carries the cost risk and final price is uncertain; in fixed-price the contractor carries the cost risk and the price is certain but is usually padded to cover that risk. GMP is a hybrid cost-plus billing with a fixed-price-style ceiling.

GMP vs Fixed Price Contract

Time & Materials (T&M) vs Fixed Price (FFP): Under T&M, the contractor is paid an agreed hourly labor rate plus the cost of materials (with markup); the owner carries the risk of unbudgeted hours and can cap exposure with a not-to-exceed/GMP. 

Under firm-fixed-price (FFP), the price is locked regardless of actual hours or material cost, so the contractor carries the risk. T&M is used when scope is fluid or must start before design is complete; FFP when scope is thoroughly documented and stable.

GMP in CMAR (Construction Manager at Risk)

How does CMAR work? 

The owner hires a construction manager during the design phase (selected on qualifications/best value, not low bid) to provide preconstruction services, then to build the project as the general contractor. The owner holds separate contracts with the designer and the CM, preserving the direct owner-architect relationship.

Why does CMAR use GMP? 

The "at risk" in CMAR is the GMP: once the CM submits and the owner accepts the GMP (via an A133 amendment), the CM is financially responsible for costs exceeding it. GMP is the mechanism that converts the CM from a consultant into a party bearing delivery risk. Unlike a general contractor, a CMAR is generally required to carry a contingency within the GMP.

Contractor responsibilities under CMAR

Constructability and cost input during design; competitive open-book subcontractor buyout; scheduling and coordination; holding and managing all subcontracts; cost reporting and audit trail; and delivering at or below the GMP.

Disadvantages of CMAR

The GMP is set on incomplete design (60-90%), creating disputes over what is "reasonably inferable" versus a change; owners can mistakenly assume total cost certainty when the GMP is conditional; the CM may value-engineer or cut corners to stay under the cap; and the owner still bears design-error risk. The CM becomes a single point of failure if inexperienced.

CM (agency) vs CMAR

A Construction Manager as Agent/Adviser (CMa) contracts only with the owner, acts as a fiduciary/adviser, does not perform construction, does not hold trade contracts, and does not guarantee a price - the owner holds the trade contracts and bears delivery risk. A CMAR holds the subcontracts, self-performs or manages the work, and guarantees the GMP. In short: CMa advises; CMAR builds and takes the risk.

Benefits of GMP

• Budget certainty: a contractual ceiling caps the owner's exposure and supports project financing.

• Cost transparency: open-book accounting lets owners see every trade cost, markup, and contingency draw in real time.

• Shared savings: underruns are split, aligning the contractor's incentives with the owner's.

• Early contractor collaboration: preconstruction input on constructability and cost prevents expensive late changes.

• Reduced disputes and faster payments: agreed GMP and open-book process reduce payment friction.

• Better cost control: progressive estimating keeps design aligned to budget before the price is locked.

Risks / Disadvantages of GMP

• Incomplete scope at GMP-setting: pricing 60-90% drawings guarantees interpretation gaps and disputes over inclusions.

• Frequent design changes: each owner-directed change adjusts the GMP and erodes cost certainty.

• Contractor-padded contingencies: thin design invites larger contingencies priced into the GMP; conversely, GCs who accept too little contingency on incomplete designs frequently lose money.

• Administrative complexity and documentation burden: open-book billing requires detailed cost substantiation, audit trails, and active owner oversight.

• Misaligned expectations: owners may treat the GMP as a firm fixed price while the CM treats it as conditional. As the Construction Management Association of America (CMAA) notes, to the CM "the GMP is a conditional number, grounded in assumptions and based on what was known or shown at the time it was set," whereas owners "often perceive the GMP as just what it sounds like - a firm, fixed price."

Roles & Responsibilities

• Owner: defines budget and program, approves the GMP, funds and controls the owner's contingency, authorizes change orders, and reviews open-book costs.

• Contractor / CM: provides preconstruction estimating and constructability input, runs competitive buyout, procures and manages subcontracts, reports costs transparently, manages the CM contingency, and delivers at or below the GMP.

• Architect / Engineer: develops and updates the design, coordinates drawings and specifications, supports cost alignment during preconstruction, and administers the contract (certifying payments and substantial completion).

GMP Change Orders and Amendments

The GMP changes only through formal mechanisms. It increases for scope additions and owner-requested changes (work beyond what was reasonably inferable from the GMP documents) differing/unforeseen site conditions, force majeure events, and, where the contract includes them, material price-escalation clauses that adjust the price for commodity movements. 

The GMP Amendment establishes the original ceiling with subsequent change orders (e.g., AIA G701, ConsensusDocs 202/203, ConsensusDocs 495) modify it. Costs above the GMP that are not covered by an approved change remain the contractor's responsibility.

A Realistic GMP Contract Example

Consider a mid-size data center - the hottest current GMP use case. According to Blackridge Research’s U.S Data Center Report, the average global data center construction cost increased from USD 7.5 million per MW to USD 10.5 million per MW between 2020 and 2025, representing a compound annual growth rate (CAGR) of approximately 7.0%.

Consider a 10 MW AI-ready data center delivered under a CMAR contract with a GMP. Using the 2025 global average construction cost of USD 10.5 million per MW, the estimated construction cost is USD 105 million.

A typical GMP could be structured as follows:

• Direct cost of the work (labor, materials, equipment, subcontractors): USD 91.5 million

• General conditions: USD 5.5 million

• CM contingency: USD 3.0 million

• Contractor's fee: USD 5.0 million

• Guaranteed Maximum Price (GMP): USD 105 million

The owner may also maintain a separate owner's contingency of around 7% (USD 7.35 million) outside the GMP to cover owner-requested scope changes or unforeseen project requirements. If efficient procurement and strong project execution reduce the actual cost of the work to USD 102.6 million, the project generates USD 2.4 million in savings below the GMP.

Under a 75/25 savings-sharing arrangement, the owner retains USD 1.8 million, while the contractor receives an additional USD 600,000 on top of its agreed fee. This structure rewards efficient delivery without compromising project scope or quality.

Conversely, if the final in-scope project cost increases to USD 107.6 million, the contractor would generally absorb the USD 2.6 million overrun because the Guaranteed Maximum Price remains fixed unless the owner approves a formal change order.

This illustrates why GMP is dominant in data centers with owners front-load procurement through a CM under a GMP to lock budgets against 2026 escalation (steel/copper tariffs and sustained copper price increases), while retaining open-book visibility and savings upside. 

Note: these figures are an illustrative synthesis using current benchmark costs, not an actual project.

When to Use GMP

GMP fits commercial construction, industrial/manufacturing plants, data centers, renewable-energy projects, infrastructure, hospitals, and universities - large, complex, or fast-tracked projects where the owner wants a cost ceiling but also wants the contractor's design-phase input.

Why GMP is popular right now:

• Data-center boom: According to Blackridge Research Datacenter Database analysis, the U.S. data center sector experienced unprecedented investment momentum in 2025, with new construction starts estimated at nearly USD 78 billion. The current global data center development pipeline exceeds 36 GW, with total planned investment ranging from USD 288 billion to USD 1.26 trillion.

• Volatile material costs: construction input prices "rose at a staggering 12.6% annualized rate during the first two months of 2026," according to ABC chief economist Anirban Basu (Associated Builders and Contractors analysis of BLS producer-price data) 

As of April 2026, steel, aluminum, and copper items made entirely or mostly from those metals carried a 50% Section 232 tariff, with derivatives at 25% and a 10% global baseline. Baseline 2026 escalation is projected at 4-6%. GMP's contingencies and escalation clauses help manage this volatility while capping owner exposure.

• Collaborative-delivery momentum: CMAR and design-build continue to gain share as owners seek early cost certainty amid schedule and supply-chain pressure. DBIA/FMI's 2024 Design-Build Utilization Study projects design-build will represent over 47% of U.S. construction spending in assessed segments by 2028.

Where to Find GMP Contract Templates / PDFs

AIA Contract Documents (current editions):

• AIA A133–2019 - Standard Form of Agreement Between Owner and Construction Manager as Constructor where the basis of payment is the Cost of the Work Plus a Fee with a Guaranteed Maximum Price.

• AIA A102–2017 - Standard Form of Agreement Between Owner and Contractor, Cost of the Work Plus a Fee with a Guaranteed Maximum Price (for a general contractor rather than a CM). Used with A201–2017 and A102 Exhibit A (Insurance and Bonds).

• AIA A103–2017 - the cost-plus-fee form without a GMP.

• AIA A101–2017 - the stipulated-sum (lump-sum) form, for contrast.

• AIA G701 - Change Order.

ConsensusDocs (CM At-Risk 500 series):

• ConsensusDocs 500 - Owner & Construction Manager Agreement (GMP with Preconstruction Services Option).

• ConsensusDocs 500.1 - the GMP Amendment used with the 500 to establish the GMP and completion dates.

• ConsensusDocs 510 - Owner/CM agreement (Cost of Work with preconstruction option, no assumed GMP).

• ConsensusDocs 410/460 - design-build cost-plus-with-GMP forms; 495 - Change Order (Cost Plus with GMP).

• ConsensusDocs 230 - Owner/Constructor agreement (Cost of the Work with a Fee and a GMP).

Conclusion

A GMP contract caps the owner's cost at a guaranteed maximum while reimbursing the contractor's actual, open-book costs plus a fee - the middle ground between rigid lump-sum and open-ended cost-plus. It is the right choice for large, complex, or fast-tracked projects where the owner wants both cost certainty and the contractor's design-phase expertise, and it is the pricing engine behind CMAR delivery.

It differs from lump sum/stipulated sum (a single opaque fixed price, contractor keeps savings), from pure cost-plus (no ceiling, owner funds everything), and from fixed price (price certain but risk-padded). Its key benefits are budget certainty, transparency, shared savings, and early collaboration; its key risks are incomplete scope at GMP-setting, change-order erosion, padded contingencies, and documentation burden.

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