Lucky

Lucky is an Invention perk which has a 0.5% chance per rank when hit that the damage dealt will be reduced to 1. This perk does not stack with Saradomin or Zamorak warpriest armour.

Lucky comes in 5 ranks, with the damage nullification chance shown below:

Given a monster's minimum $$H_{min}$$ and maximum hits $$H_{max}$$, and the rank of lucky $$R$$, the average damage reduction of the perk over $$N$$ hits can be calculated as:

$$\bigg( N \times (1-0.005R) \bigg) \times \left ( \frac{H_{min}+H_{max}}{2} \right )$$