We affirm the judgment in this mechanic’s lien foreclosure and contract action. One contention raised by appellant is that the award of prejudgment interest was not proper because there was not a conclusive determination of the exact amount due at the time of appellees’ demand upon appellant for payment. We affirm the award of prejudgment interest as proper in a suit for payment of a debt due under a contract. See Parker v. Brinson Construction Co., 78 So.2d 873 (Fla. 1955); Beckerman v. Greenbaum, 439 So.2d 233 (Fla. 2d DCA 1983); Robinson v. Peterson, 375 So.2d 294 (Fla. 2d DCA 1979); Peter Marich & Associates, Inc. v. Powell, 365 So.2d 754 (Fla. 2d DCA 1978); Town of Longboat Key v. Carl E. Widell & Son, 362 So.2d 719 (Fla. 2d DCA 1978); Vacation Prizes, Inc. v. City National Bank of Miami Beach, 227 So.2d 352 (Fla. 2d DCA 1969). Compare Federal Deposit Insurance Corp. v. Carre, 436 So.2d 227 (Fla. 2d DCA 1983) (amount of debt not established by contract).