And even then, w/o knowing what your tuning abilities are, the estimate may or may not reflect what you actually have. At best, it will be a rough estimate of the potential power your engine has.
The sim programs typically estimate to the high side of real world dynos- which themselves (dynos, I mean) vary between the dyno units, operating condition, operators themselves, whether or not a correction factor is used- and which correction factor is used, etc.