List all collections in database with its size

Open your terminal then open Mongo Shell

mongo

Select your database

use myDbName

Now paste the following code:

// Get collection names
var collectionNames = db.getCollectionNames()
var col_stats = [];

// Get stats for every collections
collectionNames.forEach(function (n) { 
    col_stats.push(db.getCollection(n).stats());
});

// Print
for (var item of col_stats) {
    print(`${item['ns']} | size: ${item['size']} 
(${(item['size']/1073741824).toFixed(2)} GB) | storageSize: ${item['storageSize']} 
(${(item['storageSize']/1073741824).toFixed(2)} GB)`);
}

Reference: https://stackoverflow.com/a/61733956/3380387