What Is Domain Authority, and How Is It Calculated by SEO Tools Like Moz and Others?


Domain Authority (DA) is a score developed by Moz that predicts how well a website will rank on search engine result pages (SERPs). This metric ranges from 1 to 100, with higher scores indicating a greater ability to rank. DA is calculated by evaluating multiple factors, including linking root domains and the number of total links, into a single DA score.

What is Domain Authority?

Domain Authority is a search engine ranking score developed by Moz that predicts a website's ability to rank on search engine result pages (SERPs). A Domain Authority score ranges from one to 100, with higher scores corresponding to a greater likelihood of ranking.

History and Purpose

Moz created Domain Authority as a comparative metric to give website owners and SEO professionals insight into a site's potential search engine rankings. Unlike PageRank, which gauges the importance of individual pages, Domain Authority aggregates various factors to give a holistic ranking ability score for a domain.

How is Domain Authority Calculated?

Domain Authority is calculated using a machine learning model against Google’s algorithm. It leverages data from the Mozscape web index and over 40 signals, including:

Linking Root Domains

Moz considers the number of unique domains that link to a website. More linking root domains generally indicate a stronger DA because it shows the site's wide recognition and authority within its niche.

This includes both the quality and quantity of incoming links. High-quality links from reputable websites significantly contribute to Domain Authority.

The value of each link is also considered. Links from highly authoritative sites contribute more to the DA score than those from less reputable sites.

Social Signals

Although it's debated among SEO professionals, some assert that social signals (like shares and mentions on social media) contribute to a site’s perceived authority.

Moz Rank (MozRank)

MozRank reflects the popularity of a website based on backlink data. It’s part of the algorithm used to gauge the strength and quality of a website's backlink profile.

Moz Trust (MozTrust)

MozTrust focuses on the trustworthiness of the backlinks. Links from highly trusted sites (like university or government websites) carry more weight.

Other Factors Considered by SEO Tools

Spam Score

Spam Score, another Moz metric, indicates the percentage of sites with similar features that have been penalized or banned by Google. A high Spam Score negatively affects Domain Authority.

Page Authority (PA)

While DA measures the domain's overall ranking potential, Page Authority examines the ranking potential of individual pages, acting as a complementary metric within SEO tools.

Website Age

Older domains generally have higher DA because they've had more time to accumulate backlinks and establish trust.

User Engagement Metrics

Metrics such as bounce rate, time on site, and the number of pages visited can indirectly impact DA by reflecting the website's overall quality and relevance.

Examples and Practical Applications

To illustrate, consider two websites: A and B. Website A has numerous backlinks from high-authority domains like educational websites, has low spam score, and consistently produces high-quality, engaging content. Website B, meanwhile, has fewer backlinks, many of which come from low-quality directories and has a higher spam score. Website A’s DA will likely be significantly higher than Website B’s.


Domain Authority is a valuable metric for understanding a website’s SEO potential compared to competitors. While it isn’t directly used by search engines to rank websites, a high DA generally correlates with higher search engine rankings. Regularly monitoring and improving DA is essential for maintaining and enhancing a website's online presence.