Get the real document BSON size in MongoDB?

You can use Object.bsonsize() to get the real document BSON size in MongoDB. This method prints the BSON size of a document in bytes, which is useful for understanding storage requirements and optimizing document structure.

Syntax

Object.bsonsize(document)

Sample Data

Let us create a collection with documents ?

db.demo477.insertMany([
    {"ClientId": 1, "ClientName": "Chris"},
    {"ClientId": 2, "ClientName": "David"},
    {"ClientId": 3, "ClientName": "Bob"}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5e82015fb0f3fa88e227908f"),
        ObjectId("5e820167b0f3fa88e2279090"),
        ObjectId("5e82016db0f3fa88e2279091")
    ]
}

Display all documents from the collection ?

db.demo477.find();

{"_id": ObjectId("5e82015fb0f3fa88e227908f"), "ClientId": 1, "ClientName": "Chris"}
{"_id": ObjectId("5e820167b0f3fa88e2279090"), "ClientId": 2, "ClientName": "David"}
{"_id": ObjectId("5e82016db0f3fa88e2279091"), "ClientId": 3, "ClientName": "Bob"}

Example: Get Document BSON Size

Get the BSON size of a document in bytes ?

Object.bsonsize(db.demo477.findOne());

62

Key Points

• Object.bsonsize() returns the size in bytes of the BSON representation
• The size includes all fields, ObjectId, and BSON overhead
• Useful for analyzing storage efficiency and document optimization

Conclusion

Use Object.bsonsize() to measure the actual storage footprint of MongoDB documents. This helps optimize document structure and understand storage requirements for your collections.