diff --git a/lib/hexdump.c b/lib/hexdump.c
index 270773b..a61cb6b 100644
--- a/lib/hexdump.c
+++ b/lib/hexdump.c
@@ -126,7 +126,7 @@
 			lx += scnprintf(linebuf + lx, linebuflen - lx,
 					"%s%16.16llx", j ? " " : "",
 					(unsigned long long)*(ptr8 + j));
-		ascii_column = 17 * ngroups + 2;
+		ascii_column = rowsize * 2 + rowsize / 8 + 2;
 		break;
 	}
 
@@ -137,7 +137,7 @@
 		for (j = 0; j < ngroups; j++)
 			lx += scnprintf(linebuf + lx, linebuflen - lx,
 					"%s%8.8x", j ? " " : "", *(ptr4 + j));
-		ascii_column = 9 * ngroups + 2;
+		ascii_column = rowsize * 2 + rowsize / 4 + 2;
 		break;
 	}
 
@@ -148,7 +148,7 @@
 		for (j = 0; j < ngroups; j++)
 			lx += scnprintf(linebuf + lx, linebuflen - lx,
 					"%s%4.4x", j ? " " : "", *(ptr2 + j));
-		ascii_column = 5 * ngroups + 2;
+		ascii_column = rowsize * 2 + rowsize / 2 + 2;
 		break;
 	}