diff --git a/src/modules/fs.cpp b/src/modules/fs.cpp
index 875cb0a6..a8e6f8ea 100644
--- a/src/modules/fs.cpp
+++ b/src/modules/fs.cpp
@@ -98,11 +98,11 @@ namespace modules {
 
         mount->bytes_total = buffer.f_bsize * buffer.f_blocks;
         mount->bytes_free = buffer.f_bsize * buffer.f_bfree;
-        mount->bytes_used = mount->bytes_total - buffer.f_bsize * buffer.f_bavail;
+        mount->bytes_used = mount->bytes_total - mount->bytes_free;
         mount->bytes_avail = buffer.f_bsize * buffer.f_bavail;
 
-        mount->percentage_free = math_util::percentage<double>(mount->bytes_avail, mount->bytes_total);
-        mount->percentage_used = math_util::percentage<double>(mount->bytes_used, mount->bytes_total);
+        mount->percentage_free = math_util::percentage<double>(mount->bytes_avail, mount->bytes_used + mount->bytes_avail);
+        mount->percentage_used = math_util::percentage<double>(mount->bytes_used, mount->bytes_used + mount->bytes_avail);
       }
     }