From the official EVE-Online website
The waste factor, for everything except Drones, is figured according to the following formula:
(0.1 / (1 + ME) )
Where ME is the number of levels of mineral levels the BP has. For drones, the formula is:
(0.05 / (1 + ME ))
In our example blueprint, the Merlin uses the former formula, or (0.1 / (1 + 5)), which ends up as .0167 roughly.
The amount of time it takes to do one level of Mineral Efficiency Research is equal to the blueprint's Research Mineral Time * (1 - 0.05 * Metallurgy Skill Level). One tip here, if you have an un-researched blueprint, the number of mineral levels to eliminate all design waste on the blueprint is equal to the single highest Wasted Ingredient on the BP, rounded down (this can also be figured by multiplying the base waste factor -0 .1 or 0.05 by the base mineral needs with the highest value).