How Is Domain Authority Calculated?

Moz calculates Domain Authority as a score from 1 to 100 using a machine-learning model trained on Google results. It looks at how many different sites link to you, how strong those sites are, and a spam signal. Nobody can run the formula by hand, and the score only compares sites to each other, not to Google.

You open a checker, see DA 23 next to your site and DA 61 next to a competitor, and want to know what to change. The honest answer starts with what the number is made of, because the inputs tell you which work moves it and which does nothing.

How is domain authority calculated?

Domain Authority is the output of a trained model, not a published formula. Moz announced Domain Authority 2.0 on February 5, 2019 and switched it on March 5, 2019, replacing a linear model with a neural network. According to PPC Land's summary of Moz's documentation, the network learns which link profiles tend to belong to sites that outrank others across thousands of search results, then scores your site by how closely your profile resembles those winners.

That means you cannot calculate it yourself. You can only feed the same inputs the model reads and watch the score respond.

What goes into the score

Four inputs carry most of the weight, and the first dwarfs the rest.

Linking root domains. The count of distinct sites linking to you. Many links from one site count for less than single links from many sites.
Total link volume. The raw number of links, discounted when they cluster on a few domains.
Strength of the linking sites. A link from a site that itself has many strong links counts for more.
Spam Score. Moz's own spam signal, which also feeds the model. Our explainer on spam score covers what triggers it.

The link data comes from Moz's own crawl. PPC Land reports that its index held more than 35 trillion links when the current model launched in 2019. Anything Moz has not crawled, it cannot count.

Why DA is a 1 to 100 scale and what the number means

The scale is non-linear, so the same effort buys fewer points as you climb. Moz's own line, as quoted by PPC Land, is that "climbing from 20 to 30 is considerably easier than climbing from 70 to 80." A new site starts at 1.

Here is a worked example with invented numbers. Site A has 40 linking domains, each with one link, and scores around the low 20s. Site B has 400 links, but 350 come from the same three directories. Site B has more links yet fewer root domains, so the model scores it close to Site A or below it. Adding ten new linking domains to Site A would move its score more than adding another 400 links to Site B.

Why did my domain authority drop?

A DA can fall without you losing a single link, because the score is relative. PPC Land gives Moz's own example: if one huge site suddenly gained a billion links, every other site's score would be pushed down a little. Other common causes:

Linking sites lost their own links, so what they pass to you shrinks.
Moz's crawler found a spammy link pointing at you and your Spam Score rose.
The crawl simply missed links it saw last month.

Before reacting, compare your referring domain count over time in a tool that crawls independently. Domain Authority vs Domain Rating explains why two tools show different numbers for the same site.

Does Google use domain authority?

No. Google has no domain authority metric in its ranking systems, according to Search Engine Journal's 2018 report on John Mueller's Reddit AMA, which concluded that "site/domain authority does not exist as a metric that is in use at Google." Moz says the same about its own score: DA has no effect on search results.

So DA is a forecasting tool. It estimates how hard a site is to outrank, based on link patterns that tend to correlate with ranking. It is useful for comparing two prospects and useless as a target. Does domain authority still matter covers where it still earns its place.

What actually raises your score

The inputs point one way: more distinct, credible sites linking to pages that deserve it. In practice that means:

Chase new linking domains, not more links from the same ones. One link from ten sites beats ten from one.
Prefer links from sites that have strong links themselves. Which backlink is best ranks the types.
Keep the profile clean. Remove or disavow obvious spam so the Spam Score input stays low.
Be patient. New links appear in Moz's index only after its crawler finds them, and the score refreshes on its schedule, not yours.

If you want a link from a real site owner in your niche without a pitch campaign, a one-for-one swap is one route, and on Backlinkster each swap is verified by API. The full tactics list is in how to increase domain authority without buying links.

Frequently asked questions

Can I calculate domain authority myself? No. Moz does not publish the model, and its link index is proprietary. You can estimate the direction by counting your referring domains, but only Moz's tool returns the score.

How does a DA PA checker work? It sends your URL to Moz's index and returns the stored Domain Authority and Page Authority. Free checkers call Moz's API or a cached copy, which is why their numbers can lag Moz's own tool.

Is domain authority the same as domain rating? No. Domain Rating is Ahrefs' separate metric, calculated from Ahrefs' own crawl. The two numbers are not interchangeable, so compare sites within one tool.

What is a good domain authority score? It depends on the sites you compete with. The scale is non-linear, so compare against the top results for your target keyword, not against a fixed number.

How often does domain authority update? Moz recalculates it as its index refreshes, and PPC Land reports no fixed schedule. Treat week-to-week changes as noise and watch the trend over months.

Does buying links raise domain authority? It can raise the number, but Google lists "buying or selling links for ranking purposes" as link spam in its spam policies. A higher DA built that way is a liability.