Pick what you actually have, what you are aiming for and how you plan to take it, and this gives you a starting range rather than a single number, because a gram is not a unit of effect. It follows the same reference points as the full dosing guide, and nothing you enter leaves your browser.
Nothing you enter leaves your browser. This is a starting point for people who have already decided to use, not a recommendation to.
Why a range, and why it starts low
Potency varies enormously between species, between batches of the same species, and even between caps and stems of the same flush. An accurate scale tells you the weight, not the psilocybin content, so the honest output is a band with a instruction attached: start at the bottom of it and treat new material as a calibration.
The dried-cubensis reference points are the widely used ones: roughly 0.5 to 1 g for a light experience, 1 to 2.5 g for a clear psychedelic one, and 2.5 to 4 g for something immersive. Fresh mushrooms run about ten times their dried weight, though the real ratio sits anywhere between 7 and 12. Fresh truffles get their own numbers rather than a conversion, because converting twice compounds the error. Lemon tek is treated as making a given amount hit harder, so the tool lowers the amount rather than raising it.
What it will not do
It will not tell you a dose is safe, and it will not scale a dose up to beat tolerance, because that is how people end up taking far more than they meant to. It also cannot tell you what you are holding: no consumer reagent reliably identifies psilocybin, which is the honest difference between this and testing MDMA. Read interactions before you dose anything, and set and setting before you decide where.