diff --git a/src/ecma119.c b/src/ecma119.c
index 5ea4402..448865f 100644
--- a/src/ecma119.c
+++ b/src/ecma119.c
@@ -137,7 +137,7 @@ size_t calc_dir_size(Ecma119Image *t, Ecma119Node *dir, size_t *ce)
      * the size of the unused space after the last directory record 
      * (ECMA-119, 6.8.1.3)
      */
-    len = div_up(len, BLOCK_SIZE) * BLOCK_SIZE;
+    len = ROUND_UP(len, BLOCK_SIZE);
 
     /* cache the len */
     dir->info.dir->len = len;
@@ -153,9 +153,9 @@ void calc_dir_pos(Ecma119Image *t, Ecma119Node *dir)
     t->ndirs++;
     dir->info.dir->block = t->curblock;
     len = calc_dir_size(t, dir, &ce_len);
-    t->curblock += div_up(len, BLOCK_SIZE);
+    t->curblock += DIV_UP(len, BLOCK_SIZE);
     if (t->rockridge) {
-        t->curblock += div_up(ce_len, BLOCK_SIZE);
+        t->curblock += DIV_UP(ce_len, BLOCK_SIZE);
     }
     for (i = 0; i < dir->info.dir->nchildren; i++) {
         Ecma119Node *child = dir->info.dir->children[i];
@@ -212,9 +212,9 @@ int ecma119_writer_compute_data_blocks(IsoImageWriter *writer)
 
     /* compute location for path tables */
     target->l_path_table_pos = target->curblock;
-    target->curblock += div_up(path_table_size, BLOCK_SIZE);
+    target->curblock += DIV_UP(path_table_size, BLOCK_SIZE);
     target->m_path_table_pos = target->curblock;
-    target->curblock += div_up(path_table_size, BLOCK_SIZE);
+    target->curblock += DIV_UP(path_table_size, BLOCK_SIZE);
     target->path_table_size = path_table_size;
 
     return ISO_SUCCESS;
@@ -392,7 +392,7 @@ int write_one_dir(Ecma119Image *t, Ecma119Node *dir)
     memset(&info, 0, sizeof(struct susp_info));
     if (t->rockridge) {
         /* initialize the ce_block, it might be needed */
-        info.ce_block = dir->info.dir->block + div_up(dir->info.dir->len, 
+        info.ce_block = dir->info.dir->block + DIV_UP(dir->info.dir->len, 
                                                       BLOCK_SIZE);
     }
 
diff --git a/src/filesrc.c b/src/filesrc.c
index 8c2cfcc..768097b 100644
--- a/src/filesrc.c
+++ b/src/filesrc.c
@@ -176,7 +176,7 @@ int filesrc_writer_compute_data_blocks(IsoImageWriter *writer)
     for (i = 0; i < size; ++i) {
         IsoFileSrc *file = filelist[i];
         file->block = t->curblock;
-        t->curblock += div_up(iso_file_src_get_size(file), BLOCK_SIZE);
+        t->curblock += DIV_UP(iso_file_src_get_size(file), BLOCK_SIZE);
     }
 
     /* the list is only needed by this writer, store locally */
@@ -260,10 +260,10 @@ int filesrc_writer_write_data(IsoImageWriter *writer)
 
         /*
          * TODO WARNING
-         * when we allow files greater than 4GB, current div_up implementation
+         * when we allow files greater than 4GB, current DIV_UP implementation
          * can overflow!!
          */
-        uint32_t nblocks = div_up(iso_file_src_get_size(file), BLOCK_SIZE);
+        uint32_t nblocks = DIV_UP(iso_file_src_get_size(file), BLOCK_SIZE);
 
         res = filesrc_open(file);
         if (res < 0) {
diff --git a/src/fs_image.c b/src/fs_image.c
index ef0fab4..376ade8 100644
--- a/src/fs_image.c
+++ b/src/fs_image.c
@@ -1110,7 +1110,7 @@ int iso_file_source_new_ifs(IsoImageFilesystem *fs, IsoFileSource *parent,
     /* Fill last entries */
     atts.st_dev = fsdata->id;
     atts.st_blksize = BLOCK_SIZE;
-    atts.st_blocks = div_up(atts.st_size, BLOCK_SIZE);
+    atts.st_blocks = DIV_UP(atts.st_size, BLOCK_SIZE);
     
     //TODO more sanity checks!!
     if (S_ISLNK(atts.st_mode) && (linkdest == NULL)) {
@@ -2076,7 +2076,7 @@ int create_boot_img_filesrc(IsoImageFilesystem *fs, IsoFileSource **src)
     /* Fill last entries */
     atts.st_dev = fsdata->id;
     atts.st_blksize = BLOCK_SIZE;
-    atts.st_blocks = div_up(atts.st_size, BLOCK_SIZE);
+    atts.st_blocks = DIV_UP(atts.st_size, BLOCK_SIZE);
     
     /* ok, we can now create the file source */
     ifsdata = calloc(1, sizeof(ImageFileSourceData));
diff --git a/src/iso1999.c b/src/iso1999.c
index 162b20d..71ad998 100644
--- a/src/iso1999.c
+++ b/src/iso1999.c
@@ -347,7 +347,7 @@ size_t calc_dir_size(Ecma119Image *t, Iso1999Node *dir)
      * the size of the unused space after the last directory record 
      * (ISO 9660:1999, 6.8.1.3)
      */
-    len = div_up(len, BLOCK_SIZE) * BLOCK_SIZE;
+    len = ROUND_UP(len, BLOCK_SIZE);
 
     /* cache the len */
     dir->info.dir->len = len;
@@ -362,7 +362,7 @@ void calc_dir_pos(Ecma119Image *t, Iso1999Node *dir)
     t->iso1999_ndirs++;
     dir->info.dir->block = t->curblock;
     len = calc_dir_size(t, dir);
-    t->curblock += div_up(len, BLOCK_SIZE);
+    t->curblock += DIV_UP(len, BLOCK_SIZE);
     for (i = 0; i < dir->info.dir->nchildren; i++) {
         Iso1999Node *child = dir->info.dir->children[i];
         if (child->type == ISO1999_DIR) {
@@ -419,9 +419,9 @@ int iso1999_writer_compute_data_blocks(IsoImageWriter *writer)
 
     /* compute location for path tables */
     t->iso1999_l_path_table_pos = t->curblock;
-    t->curblock += div_up(path_table_size, BLOCK_SIZE);
+    t->curblock += DIV_UP(path_table_size, BLOCK_SIZE);
     t->iso1999_m_path_table_pos = t->curblock;
-    t->curblock += div_up(path_table_size, BLOCK_SIZE);
+    t->curblock += DIV_UP(path_table_size, BLOCK_SIZE);
     t->iso1999_path_table_size = path_table_size;
 
     return ISO_SUCCESS;
diff --git a/src/joliet.c b/src/joliet.c
index d5494af..b0f8f49 100644
--- a/src/joliet.c
+++ b/src/joliet.c
@@ -352,7 +352,7 @@ size_t calc_dir_size(Ecma119Image *t, JolietNode *dir)
      * the size of the unused space after the last directory record 
      * (ECMA-119, 6.8.1.3)
      */
-    len = div_up(len, BLOCK_SIZE) * BLOCK_SIZE;
+    len = ROUND_UP(len, BLOCK_SIZE);
 
     /* cache the len */
     dir->info.dir->len = len;
@@ -367,7 +367,7 @@ void calc_dir_pos(Ecma119Image *t, JolietNode *dir)
     t->joliet_ndirs++;
     dir->info.dir->block = t->curblock;
     len = calc_dir_size(t, dir);
-    t->curblock += div_up(len, BLOCK_SIZE);
+    t->curblock += DIV_UP(len, BLOCK_SIZE);
     for (i = 0; i < dir->info.dir->nchildren; i++) {
         JolietNode *child = dir->info.dir->children[i];
         if (child->type == JOLIET_DIR) {
@@ -422,9 +422,9 @@ int joliet_writer_compute_data_blocks(IsoImageWriter *writer)
 
     /* compute location for path tables */
     t->joliet_l_path_table_pos = t->curblock;
-    t->curblock += div_up(path_table_size, BLOCK_SIZE);
+    t->curblock += DIV_UP(path_table_size, BLOCK_SIZE);
     t->joliet_m_path_table_pos = t->curblock;
-    t->curblock += div_up(path_table_size, BLOCK_SIZE);
+    t->curblock += DIV_UP(path_table_size, BLOCK_SIZE);
     t->joliet_path_table_size = path_table_size;
 
     return ISO_SUCCESS;
diff --git a/src/rockridge_read.c b/src/rockridge_read.c
index da082b8..9205429 100644
--- a/src/rockridge_read.c
+++ b/src/rockridge_read.c
@@ -80,7 +80,7 @@ int susp_iter_next(SuspIterator *iter, struct susp_sys_user_entry **sue)
             int nblocks;
 
             /* A CE has found, there is another continuation area */
-            nblocks = div_up(iter->ce_off + iter->ce_len, BLOCK_SIZE);
+            nblocks = DIV_UP(iter->ce_off + iter->ce_len, BLOCK_SIZE);
             iter->buffer = realloc(iter->buffer, nblocks * BLOCK_SIZE);
 
             /* read all blocks needed to cache the full CE */
diff --git a/src/util.c b/src/util.c
index bca124f..be9ac89 100644
--- a/src/util.c
+++ b/src/util.c
@@ -25,16 +25,6 @@
 #define __USE_GNU
 #include <unistd.h>
 
-inline int div_up(unsigned int n, unsigned int div)
-{
-    return (n + div - 1) / div;
-}
-
-inline int round_up(unsigned int n, unsigned int mul)
-{
-    return div_up(n, mul) * mul;
-}
-
 int int_pow(int base, int power)
 {
     int result = 1;
diff --git a/src/util.h b/src/util.h
index cba87bb..6461998 100644
--- a/src/util.h
+++ b/src/util.h
@@ -20,8 +20,8 @@
 #   define MIN(a, b) (((a) < (b)) ? (a) : (b))
 #endif
 
-int div_up(unsigned int n, unsigned int div);
-int round_up(unsigned int n, unsigned int mul);
+#define DIV_UP(n,div) ((n + div - 1) / div)
+#define ROUND_UP(n,mul) (DIV_UP(n, mul) * mul)
 
 int int_pow(int base, int power);
 
diff --git a/test/test_util.c b/test/test_util.c
index 6167409..2836dfe 100644
--- a/test/test_util.c
+++ b/test/test_util.c
@@ -55,23 +55,23 @@ static void test_strconv()
 
 static void test_div_up()
 {
-    CU_ASSERT_EQUAL( div_up(1, 2), 1 );
-    CU_ASSERT_EQUAL( div_up(2, 2), 1 );
-    CU_ASSERT_EQUAL( div_up(0, 2), 0 );
-    CU_ASSERT_EQUAL( div_up(-1, 2), 0 );
-    CU_ASSERT_EQUAL( div_up(3, 2), 2 );
+    CU_ASSERT_EQUAL( DIV_UP(1, 2), 1 );
+    CU_ASSERT_EQUAL( DIV_UP(2, 2), 1 );
+    CU_ASSERT_EQUAL( DIV_UP(0, 2), 0 );
+    CU_ASSERT_EQUAL( DIV_UP(-1, 2), 0 );
+    CU_ASSERT_EQUAL( DIV_UP(3, 2), 2 );
 }
 
 static void test_round_up()
 {
-    CU_ASSERT_EQUAL( round_up(1, 2), 2 );
-    CU_ASSERT_EQUAL( round_up(2, 2), 2 );
-    CU_ASSERT_EQUAL( round_up(0, 2), 0 );
-    CU_ASSERT_EQUAL( round_up(-1, 2), 0 );
-    CU_ASSERT_EQUAL( round_up(3, 2), 4 );
-    CU_ASSERT_EQUAL( round_up(15, 7), 21 );
-    CU_ASSERT_EQUAL( round_up(13, 7), 14 );
-    CU_ASSERT_EQUAL( round_up(14, 7), 14 );
+    CU_ASSERT_EQUAL( ROUND_UP(1, 2), 2 );
+    CU_ASSERT_EQUAL( ROUND_UP(2, 2), 2 );
+    CU_ASSERT_EQUAL( ROUND_UP(0, 2), 0 );
+    CU_ASSERT_EQUAL( ROUND_UP(-1, 2), 0 );
+    CU_ASSERT_EQUAL( ROUND_UP(3, 2), 4 );
+    CU_ASSERT_EQUAL( ROUND_UP(15, 7), 21 );
+    CU_ASSERT_EQUAL( ROUND_UP(13, 7), 14 );
+    CU_ASSERT_EQUAL( ROUND_UP(14, 7), 14 );
 }
 
 static void test_iso_lsb_msb()
@@ -695,8 +695,8 @@ void add_util_suite()
     CU_pSuite pSuite = CU_add_suite("UtilSuite", NULL, NULL);
 
     CU_add_test(pSuite, "strconv()", test_strconv);
-    CU_add_test(pSuite, "div_up()", test_div_up);
-    CU_add_test(pSuite, "round_up()", test_round_up);
+    CU_add_test(pSuite, "DIV_UP()", test_div_up);
+    CU_add_test(pSuite, "ROUND_UP()", test_round_up);
     CU_add_test(pSuite, "iso_bb()", test_iso_bb);
     CU_add_test(pSuite, "iso_lsb/msb()", test_iso_lsb_msb);
     CU_add_test(pSuite, "iso_read_lsb/msb()", test_iso_read_lsb_msb);