How to find the size of a list in C#?

A List in C# is a dynamic collection that can grow or shrink in size. To determine the size of a list, you can use two different properties: Count (for the number of actual elements) and Capacity (for the total allocated space).

Syntax

To get the number of elements in a list −

listName.Count

To get the total capacity (allocated space) of a list −

listName.Capacity

Understanding Count vs Capacity

Using Count Property

The Count property returns the actual number of elements in the list −

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main(string[] args) {
      var products = new List<string>();
      products.Add("Accessories");
      products.Add("Clothing");
      products.Add("Footwear");
      
      Console.WriteLine("Our list....");
      foreach(var p in products) {
         Console.WriteLine(p);
      }
      Console.WriteLine("Number of elements = " + products.Count);
   }
}

The output of the above code is −

Our list....
Accessories
Clothing
Footwear
Number of elements = 3

Using Capacity Property

The Capacity property returns the total number of elements the list can hold before resizing −

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main(string[] args) {
      var products = new List<string>();
      products.Add("Accessories");
      products.Add("Clothing");
      products.Add("Footwear");
      
      Console.WriteLine("Our list....");
      foreach(var p in products) {
         Console.WriteLine(p);
      }
      Console.WriteLine("Count = " + products.Count);
      Console.WriteLine("Capacity = " + products.Capacity);
   }
}

The output of the above code is −

Our list....
Accessories
Clothing
Footwear
Count = 3
Capacity = 4

Comparison

Setting Initial Capacity

You can set the initial capacity to optimize memory usage −

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main(string[] args) {
      var numbers = new List<int>(10);
      numbers.Add(1);
      numbers.Add(2);
      numbers.Add(3);
      
      Console.WriteLine("Count = " + numbers.Count);
      Console.WriteLine("Capacity = " + numbers.Capacity);
   }
}

The output of the above code is −

Count = 3
Capacity = 10

Conclusion

Use Count to get the actual number of elements in a list, which is the most common requirement. Use Capacity when you need to understand memory allocation or optimize performance by setting initial capacity.