The answer is: it depends. (C’mon, don’t sigh!)
On average, consistent link building combined with on-page optimization can deliver measurable results in a matter of months. We’ve seen our clients improve their rankings for targeted keywords in a time span of anywhere between four to twelve months.
However, there are a lot of factors that come into play. These include your domain age (newer websites take a little more time), your existing link profile (do you have spammy backlinks?), the DA of the sites that have newly linked to you (higher DA backlinks have a bigger impact) and many other factors.