Javier's script is not anymore compatible with Unity 2021, so here it is. I like to use it because it helps to identify the corresponding artifact per asset.

AssetSizeEstimation.cs

using System.IO;
using System.Linq;
using UnityEngine;
using UnityEditor;
using System.Text;
using UnityEditor.Experimental;

public class AssetSizeEstimation
{
    private static readonly string[] ExcludeRules = {"com.unity."};
    [MenuItem("Support/PrintOutPathToFileSizes")]
    public static void PrintOutPathToFileSizes()
    {
        var allAssetPaths = AssetDatabase.GetAllAssetPaths();
        int index = 0;
        StringBuilder assetPathInfo = new StringBuilder();
        assetPathInfo.Append("Project Path,Library Path, Size (bytes)");
        assetPathInfo.AppendLine();

        try
        {
            foreach (var assetPath in allAssetPaths)
            {
                if ((index % 10) == 0)
                {
                    float progress = (float) index / (float) allAssetPaths.Length;
                    EditorUtility.DisplayProgressBar("Gather path information", "Getting data", progress);
                }

                if (Directory.Exists(assetPath)) continue;
                if (ExcludeRules.Any(x => assetPath.Contains(x))) continue;

                string guidString = AssetDatabase.AssetPathToGUID(assetPath);
                ArtifactKey artifactKey = new ArtifactKey(new GUID(guidString));
                ArtifactID artifactID = AssetDatabaseExperimental.LookupArtifact(artifactKey);
                AssetDatabaseExperimental.GetArtifactPaths(artifactID, out string[] paths);

                foreach (string curVirtualPath in paths)
                {
                    var libraryPath = Path.GetFullPath(curVirtualPath);
                    if (!libraryPath.Contains("Library\\Artifacts\\")) continue;
                    var fileInfo = new FileInfo(libraryPath);
                    var fileSize = fileInfo.Length;

                    if (fileSize == 40)
                        continue;

                    var extension = (string.CompareOrdinal(fileInfo.Extension, libraryPath) == 0)
                        ? ""
                        : fileInfo.Extension;

                    assetPathInfo.Append($"{assetPath},{libraryPath},{fileSize},{extension}");
                    assetPathInfo.AppendLine();
                }

                ++index;
            }

            //Data is ready, output it to a CSV file
            var csvFilePath = "Assets/../FileSizes.csv";
            File.WriteAllText(csvFilePath, assetPathInfo.ToString());
            Debug.Log($"Data saved to: {Path.GetFullPath(csvFilePath)}");
        }
        finally
        {
            EditorUtility.ClearProgressBar();
        }
    }
}