If you’ve ever received a building estimate and wondered how the numbers were actually arrived at, the answer almost always starts in the same place: a quantity takeoff.
It’s one of those terms that gets used constantly in construction and quantity surveying, but rarely explained outside the industry. This piece covers what a takeoff actually is, how it works, why it matters, and what happens when it’s done poorly.
A quantity takeoff (sometimes written as QTO, or just a takeoff) is the process of measuring and listing all the materials required to complete a construction project. You take drawings or design information, work through them systematically, and extract every item that needs to be bought, fabricated, or installed. The result is a schedule of quantities: a detailed list of what’s needed and how much of it.
From that list, you can apply costs. Labour rates, material prices, plant and equipment. Add those up with appropriate adjustments for location, market conditions, and project complexity, and you have an estimate. Without the takeoff, you don’t have an estimate. You have a guess
For a typical residential build or extension, a thorough takeoff works through the project element by element, following a standard order.
Groundworks and foundations: Volume of excavation, concrete for strip or raft foundations, hardcore fill, blinding layers, damp proof membranes, drainage runs and fittings.
External walls: Areas of facing brick, inner skin blockwork, insulation thickness and type, cavity ties, lintels, mortar quantities.
Roofing: Roof area, truss or rafter quantities, tile or slate coverage, felt and batten, ridge and hip components, lead or EPDM for flat sections, fascia, soffit, and guttering runs.
Finishes: Floor and wall areas for plaster, screed, tiling, and decoration. Ceiling areas. Skirting and architrave runs.
The list is long because a building is made of many things. Every item that gets missed or miscounted is a potential error in the final cost plan.
These two terms are related but not the same thing. A quantity takeoff is the measurement exercise: the extraction of quantities from drawings. A bill of quantities (BOQ) is the formal document that results, presenting those quantities in a structured format that contractors can price against.
In formal procurement, particularly on larger public or commercial projects, a BOQ is prepared by the client’s cost consultant and issued to tendering contractors. All bidders price the same quantities, making their submissions directly comparable.
Under-measurement is the more dangerous of the two. If you miss a wall, forget a section of roof, or undercount window openings, the estimate will come in lower than the true cost. The contractor prices and wins the job. Then reality arrives on site. Costs rise above the contract value. Either margins are eroded or there’s a dispute with the client.
Over-measurement pushes prices up unnecessarily. If you systematically measure more material than is actually needed, your tender will be less competitive. You may lose work you could have won, or build in waste that harms your margin on successful jobs.
On major projects, this is work for a qualified quantity surveyor (QS). The QS profession exists largely because accurate measurement of complex buildings requires structured training, professional standards, and significant experience.
For residential projects, extensions, and smaller commercial work, estimators with strong trade backgrounds often carry out takeoffs. Software tools have made the process more accessible, but the quality of the output depends heavily on the person’s knowledge of how buildings go together.
You don’t need to carry out a takeoff yourself to benefit from understanding what one is. The right question to ask any estimator or builder is: how did you arrive at these quantities? A professional will be able to explain their approach. At ProQuant, every estimate we produce is based on a proper measurement of the project from the drawings or information provided. This is what allows us to provide regionally accurate cost estimates for residential projects across the UK.
You can find out more about the types of projects we cover on our estimating services pages.
A quantity takeoff is the systematic measurement of everything that goes into a building project, extracted from drawings and used as the basis for accurate cost estimation. It’s the foundation that everything else sits on. Get it right and your estimate reflects reality. Get it wrong and the consequences work their way through the entire project, from tender to final account.
With a strong foundation built from hands on site experience in his early career, Oliver Wilcox brings a practical and informed perspective to the construction industry. He went on to earn a BSc (Hons) in Building Studies, further strengthening his technical expertise and understanding of the built environment.
Following this, he spent 10 years working within the estimating sector, developing a deep knowledge of cost planning, measurement and project evaluation across residential developments.
In 2011, he co-founded Proquant Estimating LTD alongside his business partners, with a vision to deliver affordable, accurate, efficient and reliable estimating services.
Since then, the company has grown significantly and is recognised as the leading residential estimating service throughout the UK.
His combined site experience and professional expertise continues to drive Proquant’s commitment to precision, quality and client focused delivery.
