This document describes a new methodology called Extreme Software Estimation (XSoft Estimation) for accurately estimating software projects. XSoft Estimation uses COSMIC-Full Function Points (FFP) to measure software size and then applies a model of Development Effort = Size * Variable to estimate effort, cost, and schedule. The methodology was tested on 5 projects measuring their size in CFP units and comparing actual development time between expert and skilled teams, different programming languages and layers. The results showed expert teams and some languages/layers took significantly less time than others for the same sized functionality. XSoft Estimation aims to improve on past methods by basing estimates directly on measured functionality using COSMIC FFP.