diff --git a/src/applications/files/transform/PhabricatorFileImageTransform.php b/src/applications/files/transform/PhabricatorFileImageTransform.php
--- a/src/applications/files/transform/PhabricatorFileImageTransform.php
+++ b/src/applications/files/transform/PhabricatorFileImageTransform.php
@@ -7,6 +7,8 @@
   private $image;
   private $imageX;
   private $imageY;
+  const MAX_TRANSFORM_WIDTH = 4096; /* int */
+  const MAX_TRANSFORM_HEIGHT = 4096; /* int */
 
   /**
    * Get an estimate of the transformed dimensions of a file.
@@ -334,7 +336,7 @@
           'Unable to determine image width and height with getimagesize().'));
     }
 
-    $max_pixels = (4096 * 4096);
+    $max_pixels = (self::MAX_TRANSFORM_WIDTH * self::MAX_TRANSFORM_HEIGHT);
     $img_pixels = ($width * $height);
 
     if ($img_pixels > $max_pixels) {
@@ -365,6 +367,14 @@
     return $this->image;
   }
 
+  /**
+   * Get maximum supported image dimensions in pixels for transforming
+   * @return array<int> Maximum width and height
+   */
+  public static function getMaxTransformDimensions() {
+    return array(self::MAX_TRANSFORM_WIDTH, self::MAX_TRANSFORM_HEIGHT);
+  }
+
   private function shouldUseImagemagick() {
     if (!PhabricatorEnv::getEnvConfig('files.enable-imagemagick')) {
       return false;
diff --git a/src/applications/people/controller/PhabricatorPeopleProfilePictureController.php b/src/applications/people/controller/PhabricatorPeopleProfilePictureController.php
--- a/src/applications/people/controller/PhabricatorPeopleProfilePictureController.php
+++ b/src/applications/people/controller/PhabricatorPeopleProfilePictureController.php
@@ -36,6 +36,11 @@
     $e_file = true;
     $errors = array();
 
+    $max_image_dimensions =
+      PhabricatorFileImageTransform::getMaxTransformDimensions();
+    $max_image_dimensions_message = pht('Maximum image dimensions: %s pixels.',
+              implode(mb_chr(215), $max_image_dimensions));
+
     if ($request->isFormPost()) {
       $phid = $request->getStr('phid');
       $is_default = false;
@@ -254,7 +259,8 @@
           ->setName('picture')
           ->setLabel(pht('Upload Picture'))
           ->setError($e_file)
-          ->setCaption($supported_formats_message))
+          ->setCaption($supported_formats_message.' '.
+            $max_image_dimensions_message))
       ->appendChild(
         id(new AphrontFormSubmitControl())
           ->addCancelButton($done_uri)
diff --git a/src/applications/project/controller/PhabricatorProjectEditPictureController.php b/src/applications/project/controller/PhabricatorProjectEditPictureController.php
--- a/src/applications/project/controller/PhabricatorProjectEditPictureController.php
+++ b/src/applications/project/controller/PhabricatorProjectEditPictureController.php
@@ -35,6 +35,11 @@
     $e_file = true;
     $errors = array();
 
+    $max_image_dimensions =
+      PhabricatorFileImageTransform::getMaxTransformDimensions();
+    $max_image_dimensions_message = pht('Maximum image dimensions: %s pixels.',
+              implode(mb_chr(215), $max_image_dimensions));
+
     if ($request->isFormPost()) {
       $phid = $request->getStr('phid');
       $is_default = false;
@@ -261,7 +266,8 @@
           ->setName('picture')
           ->setLabel(pht('Upload Picture'))
           ->setError($e_file)
-          ->setCaption($supported_formats_message))
+          ->setCaption($supported_formats_message.' '.
+            $max_image_dimensions_message))
       ->appendChild(
         id(new AphrontFormSubmitControl())
           ->addCancelButton($manage_uri)