diff --git a/sys/dev/agp/agp.c b/sys/dev/agp/agp.c
index 39caf587b106..7d024d047246 100644
--- a/sys/dev/agp/agp.c
+++ b/sys/dev/agp/agp.c
@@ -185,7 +185,7 @@ static u_int agp_max[][2] = {
 	{2048,	1920},
 	{4096,	3932}
 };
-#define agp_max_size	(sizeof(agp_max) / sizeof(agp_max[0]))
+#define	AGP_MAX_SIZE	nitems(agp_max)
 
 /**
  * Sets the PCI resource which represents the AGP aperture.
@@ -228,12 +228,12 @@ agp_generic_attach(device_t dev)
 	 * uses a heurisitc table from the Linux driver.
 	 */
 	memsize = ptoa(realmem) >> 20;
-	for (i = 0; i < agp_max_size; i++) {
+	for (i = 0; i < AGP_MAX_SIZE; i++) {
 		if (memsize <= agp_max[i][0])
 			break;
 	}
-	if (i == agp_max_size)
-		i = agp_max_size - 1;
+	if (i == AGP_MAX_SIZE)
+		i = AGP_MAX_SIZE - 1;
 	sc->as_maxmem = agp_max[i][1] << 20U;
 
 	/*
diff --git a/sys/dev/agp/agp_ali.c b/sys/dev/agp/agp_ali.c
index 8aad840d6eae..f44cc89d61c9 100644
--- a/sys/dev/agp/agp_ali.c
+++ b/sys/dev/agp/agp_ali.c
@@ -171,7 +171,7 @@ static u_int32_t agp_ali_table[] = {
 	128*M,			/* 9 - invalid */
 	256*M,			/* 10 - invalid */
 };
-#define agp_ali_table_size (sizeof(agp_ali_table) / sizeof(agp_ali_table[0]))
+#define	AGP_ALI_TABLE_SIZE nitems(agp_ali_table)
 
 static u_int32_t
 agp_ali_get_aperture(device_t dev)
@@ -181,7 +181,7 @@ agp_ali_get_aperture(device_t dev)
 	 * I'm not sure this is correct..
 	 */
 	int i = pci_read_config(dev, AGP_ALI_ATTBASE, 4) & 0xf;
-	if (i >= agp_ali_table_size)
+	if (i >= AGP_ALI_TABLE_SIZE)
 		return 0;
 	return agp_ali_table[i];
 }
@@ -192,10 +192,10 @@ agp_ali_set_aperture(device_t dev, u_int32_t aperture)
 	int i;
 	u_int32_t attbase;
 
-	for (i = 0; i < agp_ali_table_size; i++)
+	for (i = 0; i < AGP_ALI_TABLE_SIZE; i++)
 		if (agp_ali_table[i] == aperture)
 			break;
-	if (i == agp_ali_table_size)
+	if (i == AGP_ALI_TABLE_SIZE)
 		return EINVAL;
 
 	attbase = pci_read_config(dev, AGP_ALI_ATTBASE, 4);
diff --git a/sys/dev/agp/agp_amd64.c b/sys/dev/agp/agp_amd64.c
index 56784f0ee543..f18a6a55446c 100644
--- a/sys/dev/agp/agp_amd64.c
+++ b/sys/dev/agp/agp_amd64.c
@@ -274,8 +274,7 @@ static uint32_t agp_amd64_table[] = {
 	0x80000000,	/* 2048 MB */
 };
 
-#define AGP_AMD64_TABLE_SIZE \
-	(sizeof(agp_amd64_table) / sizeof(agp_amd64_table[0]))
+#define AGP_AMD64_TABLE_SIZE nitems(agp_amd64_table)
 
 static uint32_t
 agp_amd64_get_aperture(device_t dev)