diff --git a/blivet/formats/fs.py b/blivet/formats/fs.py
index 353a9ef38..dfe5eadb5 100644
--- a/blivet/formats/fs.py
+++ b/blivet/formats/fs.py
@@ -353,17 +353,12 @@ def update_size_info(self):
         if not self.exists:
             return
 
-        self._current_info = None
         self._min_instance_size = Size(0)
         self._resizable = self.__class__._resizable
 
         # try to gather current size info
         self._size = Size(0)
-        try:
-            if self._info.available:
-                self._current_info = self._info.do_task()
-        except FSError as e:
-            log.info("Failed to obtain info for device %s: %s", self.device, e)
+        udev.settle()
         try:
             self._size = self._size_info.do_task()
         except (FSError, NotImplementedError) as e:
diff --git a/blivet/tasks/fssize.py b/blivet/tasks/fssize.py
index 504a7eabb..b8045cdc6 100644
--- a/blivet/tasks/fssize.py
+++ b/blivet/tasks/fssize.py
@@ -22,12 +22,17 @@
 import abc
 import os
 
+from .. import udev
 from ..errors import FSError
 from ..size import Size
 
 from . import fstask
 
 
+import logging
+log = logging.getLogger("blivet")
+
+
 class FSSize(fstask.FSTask, metaclass=abc.ABCMeta):
 
     """ An abstract class that represents size information extraction. """
@@ -44,10 +49,20 @@ def depends_on(self):
         return [self.fs._info]
 
     @abc.abstractmethod
-    def _get_size(self):
+    def _get_size_tools(self):
         raise NotImplementedError
 
-    # IMPLEMENTATION methods
+    def _get_size_udev(self):
+        udev.settle()
+        udev_info = udev.get_device(device_node=self.fs.device)
+        if not udev_info:
+            raise FSError("Failed to obtain udev information for device %s" % self.fs.device)
+
+        fs_size = udev.device_get_format_size(udev_info)
+        if not fs_size:
+            raise FSError("Failed to obtain filesystem size for %s from udev" % self.fs.device)
+
+        return Size(fs_size)
 
     def do_task(self):  # pylint: disable=arguments-differ
         """ Returns the size of the filesystem.
@@ -56,33 +71,51 @@ def do_task(self):  # pylint: disable=arguments-differ
             :rtype: :class:`~.size.Size`
             :raises FSError: on failure
         """
+
+        # try to get size from udev
+        try:
+            size = self._get_size_udev()
+        except FSError as e:
+            log.info("Failed to obtain filesystem size for %s from udev: %s",
+                     self.fs.device, str(e))
+        else:
+            return size
+
+        # fallback to filesystem tools
         error_msgs = self.availability_errors
         if error_msgs:
             raise FSError("\n".join(error_msgs))
 
+        if self.fs._current_info is None:
+            try:
+                if self.fs._info.available:
+                    self.fs._current_info = self.fs._info.do_task()
+            except FSError as e:
+                log.info("Failed to obtain info for device %s: %s", self.fs.device, e)
+
         if self.fs._current_info is None:
             raise FSError("No info available for size computation.")
 
-        return self._get_size()
+        return self._get_size_tools()
 
 
 class Ext2FSSize(FSSize):
-    def _get_size(self):
+    def _get_size_tools(self):
         return Size(self.fs._current_info.block_size * self.fs._current_info.block_count)
 
 
 class NTFSSize(FSSize):
-    def _get_size(self):
+    def _get_size_tools(self):
         return Size(self.fs._current_info.size)
 
 
 class XFSSize(FSSize):
-    def _get_size(self):
+    def _get_size_tools(self):
         return Size(self.fs._current_info.block_size * self.fs._current_info.block_count)
 
 
 class FATFSSize(FSSize):
-    def _get_size(self):
+    def _get_size_tools(self):
         return Size(self.fs._current_info.cluster_size * self.fs._current_info.cluster_count)
 
 
diff --git a/blivet/udev.py b/blivet/udev.py
index 73a79d418..7c453df88 100644
--- a/blivet/udev.py
+++ b/blivet/udev.py
@@ -275,6 +275,16 @@ def device_get_format_version(udev_info):
     return udev_info.get("ID_FS_VERSION")
 
 
+def device_get_format_size(udev_info):
+    """ Report a device's format size as reported by udev. """
+    return udev_info.get("ID_FS_SIZE")
+
+
+def device_get_format_blocksize(udev_info):
+    """ Report a device's format block size as reported by udev. """
+    return udev_info.get("ID_FS_BLOCKSIZE")
+
+
 def device_get_uuid(udev_info):
     """ Get the UUID from the device's format as reported by udev.