diff --git a/dump2sq.c b/dump2sq.c
index f9de1f4..9c0b8b8 100644
--- a/dump2sq.c
+++ b/dump2sq.c
@@ -369,7 +369,7 @@ int main(int argn, char **argv){
   readheader(f, &head);
   rewind(f);
 
-  if (com.GRmax == -1)  com.GRmax = head.lmax*0.5;
+  if (com.GRmax == -1)  com.GRmax = head.lmin*0.5;
   printf("Maximum cell length = %lf\n", head.lmax);
   printf("Rmax = %lf\n", com.GRmax);
   data = malloc(head.atoms * sizeof(DATA));
diff --git a/dump2sq.h b/dump2sq.h
index d792020..0fc787b 100644
--- a/dump2sq.h
+++ b/dump2sq.h
@@ -7,6 +7,7 @@
 typedef struct{
   double lx, ly, lz;
   double lmax;
+  double lmin;
   double alpha, beta, gamma;
   double M[3][3];
   double M_[3][3];
diff --git a/input.c b/input.c
index 36ac090..acf26ca 100644
--- a/input.c
+++ b/input.c
@@ -7,6 +7,9 @@ void SetMatrix(HEAD *head){
   head->lmax = head->lx;
   if (head->lmax < head->ly) head->lmax = head->ly;
   if (head->lmax < head->lz) head->lmax = head->lz;
+  head->lmin = head->lx;
+  if (head->lmin > head->ly) head->lmin = head->ly;
+  if (head->lmin > head->lz) head->lmin = head->lz;
   
   a = head->lx;
   b = head->ly;