General contractor Coastal Development & Construction I, Inc. and Titan Indemnity *1018Company (Coastal and Titan) appeal a final judgment for breach of contract in favor of T.P. and against Coastal and Titan for $47,-126.80.

Coastal and Titan claim the evidence of damages was legally insufficient to support the judgment. We agree and reverse.

At trial, the only proof of damages offered by T.P. was the unsupported opinion of T.P.’s employee as to the amount due based on a percentage of completion of the contract. This is not a permissible method to prove damages for a partially performed construction contract. See Nico Indust., Inc. v. Steel Form Contractors, Inc., 625 So.2d 1252 (Fla. 4th DCA 1993); First Atl. Bldg. Corp. v. Neubauer Constr. Co., 352 So.2d 103 (Fla. 4th DCA 1977).

In claims for breach of a partially performed construction contract, such as the one at issue in this case, the measure of damages is the subcontractor’s lost profit, together with the reasonable costs of labor and materials incurred in good faith in the course of parties’ performance of the contract. See Nico, 625 So.2d at 1252; Brooks v. Holsombach, 525 So.2d 910, 911 (Fla. 4th DCA 1988).

REVERSED.