diff --git a/include/openmc/particle.h b/include/openmc/particle.h
index ee59d73014..2917b45e4a 100644
--- a/include/openmc/particle.h
+++ b/include/openmc/particle.h
@@ -34,9 +34,6 @@ namespace openmc {
 // use to store the bins for delayed group tallies.
 constexpr int MAX_DELAYED_GROUPS {8};
 
-// Maximum number of lost particles, relative to the total number of particles
-constexpr double REL_MAX_LOST_PARTICLES {1.0e-6};
-
 constexpr double CACHE_INVALID {-1.0};
 
 //==============================================================================
diff --git a/include/openmc/settings.h b/include/openmc/settings.h
index 1dcdea3cc7..3407eadf4b 100644
--- a/include/openmc/settings.h
+++ b/include/openmc/settings.h
@@ -63,11 +63,12 @@ extern std::string path_source;
 extern std::string path_sourcepoint;      //!< path to a source file
 extern "C" std::string path_statepoint;   //!< path to a statepoint file
 
-extern "C" int32_t n_batches;             //!< number of (inactive+active) batches
-extern "C" int32_t n_inactive;            //!< number of inactive batches
-extern "C" int32_t n_max_lost_particles;  //!< maximum number of lost particles
-extern "C" int32_t gen_per_batch;         //!< number of generations per batch
-extern "C" int64_t n_particles;           //!< number of particles per generation
+extern "C" int32_t n_batches;                //!< number of (inactive+active) batches
+extern "C" int32_t n_inactive;               //!< number of inactive batches
+extern "C" int32_t n_max_lost_particles;     //!< maximum number of lost particles
+extern double relative_max_lost_particles;   //!< maximum number of lost particles, relative to the total number of particles
+extern "C" int32_t gen_per_batch;            //!< number of generations per batch
+extern "C" int64_t n_particles;              //!< number of particles per generation
 
 
 extern int64_t max_particles_in_flight; //!< Max num. event-based particles in flight
diff --git a/openmc/lib/settings.py b/openmc/lib/settings.py
index a25ccb962f..8345e00881 100644
--- a/openmc/lib/settings.py
+++ b/openmc/lib/settings.py
@@ -23,6 +23,7 @@ class _Settings(object):
     generations_per_batch = _DLLGlobal(c_int32, 'gen_per_batch')
     inactive = _DLLGlobal(c_int32, 'n_inactive')
     max_lost_particles = _DLLGlobal(c_int32, 'n_max_lost_particles')
+    rel_max_lost_particles = _DLLGlobal(c_double, 'relative_max_lost_particles')
     particles = _DLLGlobal(c_int64, 'n_particles')
     restart_run = _DLLGlobal(c_bool, 'restart_run')
     run_CE = _DLLGlobal(c_bool, 'run_CE')
diff --git a/openmc/settings.py b/openmc/settings.py
index 79e7719a3d..794c97b618 100644
--- a/openmc/settings.py
+++ b/openmc/settings.py
@@ -60,6 +60,8 @@ class Settings(object):
         Number of generations per batch
     max_lost_particles : int
         Maximum number of lost particles       
+    rel_max_lost_particles : int
+        Maximum number of lost particles, relative to the total number of particles      
     inactive : int
         Number of inactive batches
     keff_trigger : dict
@@ -179,6 +181,7 @@ class Settings(object):
         self._generations_per_batch = None
         self._inactive = None
         self._max_lost_particles = None
+        self._rel_max_lost_particles = None
         self._particles = None
         self._keff_trigger = None
 
@@ -261,6 +264,10 @@ class Settings(object):
     def max_lost_particles(self):
         return self._max_lost_particles        
 
+    @property
+    def rel_max_lost_particles(self):
+        return self._rel_max_lost_particles         
+
     @property
     def particles(self):
         return self._particles
@@ -430,6 +437,13 @@ class Settings(object):
         cv.check_greater_than('max_lost_particles', max_lost_particles, 0)
         self._max_lost_particles = max_lost_particles        
 
+    @rel_max_lost_particles.setter
+    def rel_max_lost_particles(self, rel_max_lost_particles):
+        cv.check_type('rel_max_lost_particles', rel_max_lost_particles, Real)
+        cv.check_greater_than('rel_max_lost_particles', rel_max_lost_particles, 0)
+        cv.check_less_than('rel_max_lost_particles', rel_max_lost_particles, 1)
+        self._rel_max_lost_particles = rel_max_lost_particles          
+
     @particles.setter
     def particles(self, particles):
         cv.check_type('particles', particles, Integral)
@@ -779,7 +793,12 @@ class Settings(object):
     def _create_max_lost_particles_subelement(self, root):
         if self._max_lost_particles is not None:
             element = ET.SubElement(root, "max_lost_particles")
-            element.text = str(self._max_lost_particles)            
+            element.text = str(self._max_lost_particles)    
+
+    def _create_rel_max_lost_particles_subelement(self, root):
+        if self._rel_max_lost_particles is not None:
+            element = ET.SubElement(root, "rel_max_lost_particles")
+            element.text = str(self._rel_max_lost_particles)                     
 
     def _create_particles_subelement(self, root):
         if self._particles is not None:
@@ -1028,6 +1047,7 @@ class Settings(object):
             self._batches_from_xml_element(elem)
             self._inactive_from_xml_element(elem)
             self._max_lost_particles_from_xml_element(elem)
+            self._rel_max_lost_particles_from_xml_element(elem)
             self._generations_per_batch_from_xml_element(elem)
 
     def _run_mode_from_xml_element(self, root):
@@ -1053,7 +1073,12 @@ class Settings(object):
     def _max_lost_particles_from_xml_element(self, root):
         text = get_text(root, 'max_lost_particles')
         if text is not None:
-            self.max_lost_particles = int(text)            
+            self.max_lost_particles = int(text)     
+
+    def _rel_max_lost_particles_from_xml_element(self, root):
+        text = get_text(root, 'rel_max_lost_particles')
+        if text is not None:
+            self.rel_max_lost_particles = float(text)                       
 
     def _generations_per_batch_from_xml_element(self, root):
         text = get_text(root, 'generations_per_batch')
@@ -1295,6 +1320,7 @@ class Settings(object):
         self._create_batches_subelement(root_element)
         self._create_inactive_subelement(root_element)
         self._create_max_lost_particles_subelement(root_element)
+        self._create_rel_max_lost_particles_subelement(root_element)
         self._create_generations_per_batch_subelement(root_element)
         self._create_keff_trigger_subelement(root_element)
         self._create_source_subelement(root_element)
@@ -1366,6 +1392,7 @@ class Settings(object):
         settings._batches_from_xml_element(root)
         settings._inactive_from_xml_element(root)
         settings._max_lost_particles_from_xml_element(root)
+        settings._rel_max_lost_particles_from_xml_element(root)
         settings._generations_per_batch_from_xml_element(root)
         settings._keff_trigger_from_xml_element(root)
         settings._source_from_xml_element(root)
diff --git a/openmc/statepoint.py b/openmc/statepoint.py
index 051195ec96..0d78bf68dc 100644
--- a/openmc/statepoint.py
+++ b/openmc/statepoint.py
@@ -79,6 +79,8 @@ class StatePoint(object):
         Number of inactive batches
     n_max_lost_particles : int
         Number of max lost particles
+    relative_max_lost_particles : float
+        Number of max lost particles, relative to the total number of particles
     n_particles : int
         Number of particles per generation
     n_realizations : int
@@ -316,7 +318,11 @@ class StatePoint(object):
 
     @property
     def n_max_lost_particles(self):
-        return self._f['n_max_lost_particles'][()]            
+        return self._f['n_max_lost_particles'][()]  
+
+    @property
+    def relative_max_lost_particles(self):
+        return self._f['relative_max_lost_particles'][()]                    
 
     @property
     def n_particles(self):
diff --git a/src/particle.cpp b/src/particle.cpp
index 8e66222048..79e6625771 100644
--- a/src/particle.cpp
+++ b/src/particle.cpp
@@ -164,8 +164,6 @@ Particle::event_calculate_xs()
     if (cell_born_ == C_NONE) cell_born_ = coord_[n_coord_ - 1].cell;
   }
 
-  std::cout << "settings::n_max_lost_particles " << settings::n_max_lost_particles << std::endl;
-
   // Write particle track.
   if (write_track_) write_particle_track(*this);
 
@@ -630,12 +628,10 @@ Particle::mark_as_lost(const char* message)
   auto n = simulation::current_batch * settings::gen_per_batch *
     simulation::work_per_rank;
 
-   std::cout << simulation::n_lost_particles << "HELLLOOOOOOOOOOOO MS DOUBTFIRE" << std::endl;    
-
   // Abort the simulation if the maximum number of lost particles has been
   // reached
   if (simulation::n_lost_particles >= settings::n_max_lost_particles &&
-      simulation::n_lost_particles >= REL_MAX_LOST_PARTICLES*n) {
+      simulation::n_lost_particles >= settings::relative_max_lost_particles*n) {
     fatal_error("Maximum number of lost particles has been reached.");
   }
 }
diff --git a/src/settings.cpp b/src/settings.cpp
index 41a55501c2..d72e5f17f7 100644
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -80,6 +80,7 @@ std::string path_statepoint;
 int32_t n_batches;
 int32_t n_inactive {0};
 int32_t n_max_lost_particles {10};
+double relative_max_lost_particles {1.0e-6};
 int32_t gen_per_batch {1};
 int64_t n_particles {-1};
 
@@ -149,6 +150,11 @@ void get_run_parameters(pugi::xml_node node_base)
     n_max_lost_particles = std::stoi(get_node_value(node_base, "max_lost_particles"));
   }  
 
+  // Get relative number of lost particles
+  if (check_for_node(node_base, "rel_max_lost_particles")) {
+    relative_max_lost_particles = std::stod(get_node_value(node_base, "rel_max_lost_particles"));
+  }    
+
   // Get number of inactive batches
   if (run_mode == RunMode::EIGENVALUE) {
     if (check_for_node(node_base, "inactive")) {
@@ -358,7 +364,9 @@ void read_settings_xml()
       fatal_error("Number of particles must be greater than zero.");
     } else if (n_max_lost_particles <= 0) {
       fatal_error("Number of max lost particles must be greater than zero.");
-    }    
+    } else if (relative_max_lost_particles <= 0.0 || relative_max_lost_particles >= 1.0) {
+      fatal_error("Relative max lost particles must be between zero and one.");
+    }       
   }
 
   // Copy random number seed if specified