diff --git a/mytools/particleInfo.cpp b/mytools/particleInfo.cpp
index 22fda35..ccc0d82 100644
--- a/mytools/particleInfo.cpp
+++ b/mytools/particleInfo.cpp
@@ -22,6 +22,9 @@ bool loadParticleInfo(ParticleInfo& info,
   info.ranges[2][0] = f_info.get_att("range_z_min")->as_double(0);
   info.ranges[2][1] = f_info.get_att("range_z_max")->as_double(0);
 
+  for (int i = 0; i < 3; i++)
+    info.length[i] = info.ranges[i][1] - info.ranges[i][0];
+
   try
     {
       UnformattedRead f(particles);
diff --git a/mytools/particleInfo.hpp b/mytools/particleInfo.hpp
index b37555a..f8397c1 100644
--- a/mytools/particleInfo.hpp
+++ b/mytools/particleInfo.hpp
@@ -14,6 +14,7 @@ struct ParticleInfo
 {
   ParticleVector particles;
   float ranges[3][2];
+  float length[3];
 };
 
 bool loadParticleInfo(ParticleInfo& info,