In MongoDB the db.collection.count() method returns the count of documents that would match a find() query for the collection or view.

The collection part is the name of the collection or view to perform the count operation on.

Note that it doesn’t actually perform a find() operation. It simply counts and returns the number of results that match a query.

Example

Suppose we have a collection called pets with the following documents:

{ "_id" : 1, "name" : "Wag", "type" : "Dog", "weight" : 20 }
{ "_id" : 2, "name" : "Bark", "type" : "Dog", "weight" : 10 }
{ "_id" : 3, "name" : "Meow", "type" : "Cat", "weight" : 7 }
{ "_id" : 4, "name" : "Scratch", "type" : "Cat", "weight" : 8 }
{ "_id" : 5, "name" : "Bruce", "type" : "Bat", "weight" : 3 }
{ "_id" : 6, "name" : "Fetch", "type" : "Dog", "weight" : 17 }
{ "_id" : 7, "name" : "Jake", "type" : "Dog", "weight" : 30 }

We can use the following query to return the number of documents in the collection:

db.pets.count()

Result:

7

This is the equivalent of doing the following:

db.pets.find().count()

Result:

7

The MongoDB documentation actually advises against using db.collection.count() without a query predicate. This is because the method returns results based on the collection’s metadata, which may result in an approximate count.

Count the Result of a Query

You can count the result of a query by passing the query criteria.

Example:

db.pets.count({
    "type": "Dog"
})

Result:

4

In this example, we found out that there are four dogs in the collection.

Let’s check the count of another query. This time we’ll find out how many pets have a weight greater than a certain amount.

db.pets.count({
    "weight": { $gt: 10 }
})

Result:

3

Limit the Count

You can use the limit parameter to specify a maximum number of documents to count.

Example:

db.pets.count( {}, { limit: 5 } )

Result:

5

We saw before that there are actually 7 documents in this collection, but in this example we limited it to count a maximum of 5.

If the limit is higher than the actual count, then the result won’t be affected by the limit argument.

Example:

db.pets.count( {}, { limit: 10 } )

Result:

7

Skipping Documents

You can count use the skip parameter to skip a number of documents before counting.

Example:

db.pets.count( {}, { skip: 5 } )

Result:

2

Deprecation

Note that the MongoDB documentation states the following:

MongoDB drivers compatible with the 4.0 features deprecate their respective cursor and collection count() APIs in favor of new APIs for countDocuments() and estimatedDocumentCount(). For the specific API names for a given driver, see the driver documentation.

More Information

The db.collection.count() method is a wrapper for the count command.

The db.collection.count() method accepts other parameters, such as hint, maxTimeMS, readConcern, and collation.

See the MongoDB documentation for more information.