"Send me an estimation" and "send me a BOQ" get treated as the same request by a lot of clients — and by more than a few contractors who'd rather you not notice the difference. They're related, but they protect you in different ways, and mixing them up is one of the more common ways a Kolkata construction budget quietly drifts.
Estimation: A Ballpark, Made Early
An estimation is a projected cost, usually built from area-based rates (per square foot) or broad historical benchmarks, produced before detailed drawings exist. It's genuinely useful — for feasibility decisions, for approaching a bank for a loan, for deciding whether a project is worth pursuing at all.
What it isn't: a commitment to a final price. An estimation can be off by a meaningful margin once real design, real site conditions, and real material specifications enter the picture.
BOQ: The Itemized, Measurable Version
A Bill of Quantities (BOQ) is a detailed, itemized list of every material, quantity, and labor component required for the project, each priced individually — cubic meters of concrete, square meters of tiling, running meters of electrical conduit, and so on, all tied to the actual approved drawings.
Because a BOQ is itemized, it's verifiable. You can walk onto a site partway through construction and check whether the quantity of steel or concrete actually used matches what was billed against the BOQ. You cannot do that with a rough estimation — there's nothing granular enough to check against.
An estimation tells you roughly what the project might cost. A BOQ is the tool that lets you verify what it's actually costing, line by line, as it happens.
Where Projects Actually Lose Money
The exposure isn't usually in the estimation stage — it's when a client treats an early estimation as if it were a locked BOQ, signs a contract against it, and then has no itemized reference to check contractor billing against once construction starts. Overbilling, quantity padding, and "extra work" claims are far easier to push through when there's no BOQ line item to point to and say "this doesn't match."
The practical takeaway: treat an estimation as a planning tool, and insist on a proper BOQ — verified against actual approved drawings — before any construction contract is signed. It's the single document that gives you (or your PMC) something concrete to audit contractor bills against for the rest of the project.