An estimate is an informed view of likely cost — useful at feasibility, not contractually binding. A quote is a price offered against a defined scope — usually binding subject to the scope being correct. A fixed price is exactly what it says: a commitment to deliver the defined scope for that number, with variations only if scope changes.

Each has its place. Estimates are right at conception. Quotes are right when scope is reasonably defined. Fixed prices are right when the specification is complete and the contractor has had the chance to price it properly.

Confusion between the three causes more disputes than any other single thing in domestic construction.