diff --git a/notebook/services/api/api.yaml b/notebook/services/api/api.yaml
index 9024fbd55..4cf8f9c9d 100644
--- a/notebook/services/api/api.yaml
+++ b/notebook/services/api/api.yaml
@@ -817,7 +817,7 @@ definitions:
       size:
         type: integer
         description: "The size of the file or directory."
-        formate: bytes
+        format: bytes
       mimetype:
         type: string
         description: "The mimetype of a file.  If content is not null, and type is 'file', this will contain the mimetype of the file, otherwise this will be null."
diff --git a/notebook/services/contents/filemanager.py b/notebook/services/contents/filemanager.py
index b716c1822..e0a5af37e 100644
--- a/notebook/services/contents/filemanager.py
+++ b/notebook/services/contents/filemanager.py
@@ -190,10 +190,8 @@ class FileContentsManager(FileManagerMixin, ContentsManager):
         except (ValueError, OSError):
             self.log.warning('Unable to get size.')
             size = None
-            
         return size
 
-
     def file_exists(self, path):
         """Returns True if the file exists, else returns False.
 
@@ -272,7 +270,6 @@ class FileContentsManager(FileManagerMixin, ContentsManager):
             self.log.warning('Invalid ctime %s for %s', info.st_ctime, os_path)
             created = datetime(1970, 1, 1, 0, 0, tzinfo=tz.UTC)
 
-
         # Create the base model.
         model = {}
         model['name'] = path.rsplit('/', 1)[-1]
@@ -362,7 +359,6 @@ class FileContentsManager(FileManagerMixin, ContentsManager):
 
         os_path = self._get_os_path(path)
         model['mimetype'] = mimetypes.guess_type(os_path)[0]
-                
         model['size'] = self._get_file_size(os_path)
 
         if content:
@@ -391,7 +387,6 @@ class FileContentsManager(FileManagerMixin, ContentsManager):
         model['type'] = 'notebook'
         os_path = self._get_os_path(path)
         model['size'] = self._get_file_size(os_path)
-
         
         if content:
             nb = self._read_notebook(os_path, as_version=4)
@@ -400,7 +395,6 @@ class FileContentsManager(FileManagerMixin, ContentsManager):
             model['format'] = 'json'
             self.validate_notebook_model(model)
             
-            
         return model
 
     def get(self, path, content=True, type=None, format=None):
diff --git a/notebook/static/base/js/utils.js b/notebook/static/base/js/utils.js
index 588e6edd0..ef00a6d47 100644
--- a/notebook/static/base/js/utils.js
+++ b/notebook/static/base/js/utils.js
@@ -1038,21 +1038,33 @@ define([
             return (order == 1) ? 1 : -1;
         }
     };
+    
+    // source: https://github.com/sindresorhus/pretty-bytes
+    var format_filesize = function(num) {
+      if (num === undefined)
+        return;
 
-    var format_filesize = function(filesize) {
-      if (filesize) {
-        var units = ['B', 'kB', 'MB', 'GB', 'TB'];
-        var base = 1000;
-        if (Math.abs(filesize) < base){
-          return filesize + " B";
-        }
-        var u = -1;
-        do {
-          filesize /= base;
-          u++;
-        } while(Math.abs(filesize) >= base && u < units.length - 1);
-        return filesize.toFixed(1) + " " + units[u];
+      var UNITS = ['B', 'kB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'];
+
+      if (!Number.isFinite(num)) {
+        console.error(`Expected a finite number, got ${typeof num}: ${num}`);
       }
+
+      var neg = num < 0;
+
+      if (neg) {
+        num = -num;
+      }
+
+      if (num < 1) {
+        return (neg ? '-' : '') + num + ' B';
+      }
+
+      var exponent = Math.min(Math.floor(Math.log10(num) / 3), UNITS.length - 1);
+      var numStr = Number((num / Math.pow(1000, exponent)).toPrecision(3));
+      var unit = UNITS[exponent];
+
+      return (neg ? '-' : '') + numStr + ' ' + unit;
     }
 
     // javascript stores text as utf16 and string indices use "code units",