There are several reasons you may want to estimate the traffic a website receives. If you own the website, there is no reason to guess; Google Analytics provides exact numbers, and it’s free. There are other free and paid website analytics programs as well. Many of the free programs use data from Google Analytics and present it in a more organized fashion or offer insights based on the data.
A few SEO firms are suggesting you should base your SEO investment on the potential amount of traffic you can expect to receive. They take keywords they will try to rank your site for and their search volume and they decide where your site could potentially rank. Estimating the highest rank your site may achieve, estimating keyword search volume and the percentage of people who click on each search result position will give you a figure which is most likely a wild estimate of your potential traffic.
You could also want to estimate a competitor's website traffic numbers. There are traffic estimation tools which use a variety of methods to estimate the total number of visitors a website receives. Traffic estimation tools may monitor devices and obtain data from internet service providers. SEO tool, such as Ahrefs also provide traffic estimates using keywords your website ranks for, your site's position and the number of monthly searches for the keyword. If you ranked second for living room furniture and the second position get 30 percent of the traffic from a monthly search for the keyword, you can get an estimate of your traffic. If you want to know the traffic a domain for sale receives, you can also use these two methods if you suspect the analytics.
If your competitors are making money from advertising, they may post their monthly number of visitors on their Advertise on this Site page. Some webmasters will overstate their traffic stats so you have to be careful. For more information click here https://www.reddit.com/r/SEO/comments/cuc30d/whydonttheorganictrafficnumbersreported_by/.