The software engineering community has been trying to find a way to get fast and accurate software estimations for many years. Although many methods have been proposed, they are not designed for novice persons. This paper proposes a collaborative estimation method based on negotiation. The method is applicable to small/medium-size projects (3-6 months) and it can be used by novice developers. The article also describes a software application supporting the process. The estimation method and the tool where evaluated in an academic scenario. The obtained results show this kind of tool is suitable for novice developers; however, an in-depth study must be made to determine the real effectiveness of the application.