Mean reciprocal rank

Mean reciprocal rank, or MRR, rewards placing the first relevant result near the top.

Begin with the denominator

If three questions have their first relevant result at ranks 1, 2, and 5:

MRR = (1/1 + 1/2 + 1/5) / 3
    = (1 + 0.5 + 0.2) / 3
    = 0.567

A question with no relevant result contributes 0 under the usual convention.

FDE note

MRR ignores every relevant item after the first. It fits lookup experiences where one strong result is enough; pair it with Recall@k when an answer needs several passages.