diff --git a/include/ntfs/rich.h b/include/ntfs/rich.h
index b40a7a4f..c0cb85b7 100644
--- a/include/ntfs/rich.h
+++ b/include/ntfs/rich.h
@@ -26,9 +26,7 @@
 #include "attrib.h"
 #include "bitmap.h"
 
-#define ROUND_UP(num,bound) (((num)+((bound)-1)) & ~((bound)-1))
-#define ROUND_DOWN(num,bound) ((num) & ~((bound)-1))
-#define ATTR_SIZE(s) ROUND_UP(s,8)
+#define ATTR_SIZE(s) ROUND_UP(s, 3)
 
 ATTR_RECORD * find_attribute(const ATTR_TYPES type, ntfs_attr_search_ctx *ctx);
 ATTR_RECORD * find_first_attribute(const ATTR_TYPES type, MFT_RECORD *mft);
diff --git a/include/ntfs/support.h b/include/ntfs/support.h
index 76114d6a..11844c31 100644
--- a/include/ntfs/support.h
+++ b/include/ntfs/support.h
@@ -60,6 +60,13 @@
 #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
 #endif
 
+/*
+ * Round up and down @num to 2 in power of @order.
+ */
+#define ROUND_UP(num,order)	(((num) + ((1 << order) - 1)) & \
+				~((1 << order) - 1))
+#define ROUND_DOWN(num,order)	((num) & ~((1 << order) - 1))
+
 /*
  * Simple bit operation macros. NOTE: These are NOT atomic.
  */
diff --git a/libntfs/bitmap.c b/libntfs/bitmap.c
index 4076ad90..25e7455a 100644
--- a/libntfs/bitmap.c
+++ b/libntfs/bitmap.c
@@ -401,9 +401,9 @@ int ntfs_bmp_add_data(struct ntfs_bmp *bmp, VCN vcn, u8 *data)
 		return -1;
 
 	ntfs_log_trace ("\n");
-	old = ROUND_UP(bmp->count, 16);
+	old = ROUND_UP(bmp->count, 4);
 	bmp->count++;
-	new = ROUND_UP(bmp->count, 16);
+	new = ROUND_UP(bmp->count, 4);
 
 	if (old != new) {
 		bmp->data     = realloc(bmp->data,      new * sizeof(*bmp->data));
@@ -513,8 +513,8 @@ int ntfs_bmp_set_range(struct ntfs_bmp *bmp, VCN vcn, s64 length, int value)
 	vcn_finish = vcn + length - 1;
 
 	//ntfs_log_debug("vcn_start = %d, vcn_finish = %d\n", vcn_start, vcn_finish);
-	a = ROUND_DOWN(vcn_start,  csib);
-	b = ROUND_DOWN(vcn_finish, csib) + 1;
+	a = ROUND_DOWN(vcn_start,  bmp->vol->cluster_size_bits + 3);
+	b = ROUND_DOWN(vcn_finish, bmp->vol->cluster_size_bits + 3) + 1;
 
 	//ntfs_log_debug("a = %lld, b = %lld\n", a, b);
 
@@ -598,7 +598,7 @@ s64 ntfs_bmp_find_last_set(struct ntfs_bmp *bmp)
 	// find cluster size of bmp
 
 	byte_count = bmp->attr->data_size;
-	clust_count = ROUND_UP(byte_count, bmp->vol->cluster_size) >> bmp->vol->cluster_size_bits;
+	clust_count = ROUND_UP(byte_count, bmp->vol->cluster_size_bits) >> bmp->vol->cluster_size_bits;
 
 	//ntfs_log_debug("bitmap = %lld bytes\n", byte_count);
 	//ntfs_log_debug("bitmap = %lld buffers\n", clust_count);
diff --git a/libntfs/dir.c b/libntfs/dir.c
index aef26af0..95a47574 100644
--- a/libntfs/dir.c
+++ b/libntfs/dir.c
@@ -1750,7 +1750,7 @@ int ntfs_dir_truncate(ntfs_volume *vol, struct ntfs_dir *dir)
 		return 0;
 
 #if 0
-	buf_count = ROUND_UP(dir->bitmap->attr->allocated_size, vol->cluster_size) >> vol->cluster_size_bits;
+	buf_count = ROUND_UP(dir->bitmap->attr->allocated_size, vol->cluster_size_bits) >> vol->cluster_size_bits;
 	ntfs_log_debug("alloc = %lld bytes\n", dir->ialloc->allocated_size);
 	ntfs_log_debug("alloc = %lld clusters\n", dir->ialloc->allocated_size >> vol->cluster_size_bits);
 	ntfs_log_debug("bitmap bytes 0 to %lld\n", ((dir->ialloc->allocated_size >> vol->cluster_size_bits)-1)>>3);