diff --git a/src/fix_rigid.cpp b/src/fix_rigid.cpp
index 76e7f98fde..0d72754d85 100644
--- a/src/fix_rigid.cpp
+++ b/src/fix_rigid.cpp
@@ -991,13 +991,20 @@ int FixRigid::dof(int igroup)
   int *nall = new int[nbody];
   MPI_Allreduce(ncount,nall,nbody,MPI_INT,MPI_SUM,world);
 
-  // remove 3N - 6 dof for each rigid body if more than 2 atoms in igroup
-  // remove 3N - 5 dof for each diatomic rigid body in igroup
+  // remove d*N - d(d+1)/2 dof for each rigid body if more than 2 atoms in igroup
+  // http://en.wikipedia.org/wiki/Degrees_of_freedom_(engineering)
+  // remove an additional dof for each diatomic rigid body in igroup if d=3
 
   int n = 0;
-  for (int ibody = 0; ibody < nbody; ibody++) {
-    if (nall[ibody] > 2) n += 3*nall[ibody] - 6;
-    else if (nall[ibody] == 2) n++;
+  if (domain->dimension == 3) {
+    for (int ibody = 0; ibody < nbody; ibody++) {
+      if (nall[ibody] > 2) n += 3*nall[ibody] - 6;
+      else if (nall[ibody] == 2) n++;
+    }
+  } else if (domain->dimension == 2) {
+    for (int ibody = 0; ibody < nbody; ibody++) {
+      if (nall[ibody] > 1) n += 2*nall[ibody] - 3;
+    }
   }
 
   delete [] ncount;