Software Estimation: Demystifying the Black Art (Best Practices (Microsoft))

Use software tools based on the science of estimation to most accurately compute effort estimates from your size estimates.

Use industry-average effort graphs to obtain rough effort estimates in the wide part of the Cone of Uncertainty. For larger projects, remember that more powerful estimation techniques are easily cost-justified.

Use the ISBSG method to compute a rough effort estimate. Combine it with other methods, and look for convergence or spread among the different estimates.

Not all estimation methods are equal. When looking for convergence or spread among estimates, give more weight to the techniques that tend to produce the most accurate results.