This is of course one of the first and most important questions any client we pitch our Digital Marketing - and in particular Search Engine Optimization services – to asks us.
Luckily, The Website Group, in association with ahrefs, have put together empirical data, which is in line with our own findings, in a well drawn up infographic.
The study finds that it typically takes at least 1 year of SEO activities to rank on the first page of Google search results for longer tail, lower search volume keywords. While positions 1-3 usually take a minimum of 2 years, with the median lying somewhere in the 3+ years range. Domain Rating (DR) was the biggest supporting indicator of this correlation. A high DR is vital for prime search result placements.
We’re really thankful for a study like this, it draws upon findings from a significantly large data set and makes it easier to see the correlation between effective SEO activities, time spent on optimization, and higher SERPs (Search Engine Ranking Positions).
Here’s the infographic: 
Credit: https://thewebsitegroup.co.uk/infographics/how-long-to-rank-google/