You can use the following methods to calculate the sum of values in a field in MongoDB:

**Method 1: Calculate Sum of Field**

db.collection.aggregate([{$group: {_id:null, sum_val:{$sum:"$valueField"}}}])

**Method 2: Calculate Sum of Field by Group**

db.collection.aggregate([{$group: {_id:"$groupField", sum_val:{$sum:"$valueField"}}}])

The following examples show how to use each method with a collection teams with the following documents:

db.teams.insertOne({team: "Mavs", points: 30, rebounds: 8}) db.teams.insertOne({team: "Mavs", points: 30, rebounds: 12}) db.teams.insertOne({team: "Spurs", points: 20, rebounds: 7}) db.teams.insertOne({team: "Spurs", points: 25, rebounds: 5}) db.teams.insertOne({team: "Spurs", points: 25, rebounds: 9})

**Example 1: Calculate Sum of Field**

We can use the following code to calculate the sum of values in the **points** field:

db.teams.aggregate([{$group: {_id:null, sum_val:{$sum:"$points"}}}])

This query returns the following results:

{ _id: null, sum_val: 130}

From the results we can see that the sum of values in the points field is **130**.

We can manually verify this is correct by calculating the sum of the points values by hand:

Sum of Points: 30 + 30 + 20 + 25 + 25 = **130**.

**Example 2: Calculate Sum of Field by Group**

We can use the following code to calculate the sum of the values in the **points** field, grouped by the **team** field:

db.teams.aggregate([{$group: {_id:"$team", sum_val:{$sum:"$points"}}}])

This query returns the following results:

{ _id: 'Spurs', sum_val: 60 } { _id: 'Mavs', sum_val: 70 }

From the results we can see:

- The sum of points for the Spurs is
**60**. - The sum of points for the Mavs is
**70**.

**Note**: You can find the complete documentation for the **$sum **function here.

**Additional Resources**

The following tutorials explain how to perform other common operations in MongoDB:

How to Calculate the Median Value in MongoDB

How to Calculate the Average Value in MongoDB

How to Calculate the Max Value in MongoDB