diff --git a/sys/compat/linux/linux_socket.c b/sys/compat/linux/linux_socket.c
index 741a45bb1bb5..105aec5230ab 100644
--- a/sys/compat/linux/linux_socket.c
+++ b/sys/compat/linux/linux_socket.c
@@ -1703,7 +1703,7 @@ static const unsigned char lxs_args[] = {
 	LINUX_AL(4) /* sendmmsg */
 };
 
-#define	LINUX_AL_SIZE	sizeof(lxs_args) / sizeof(lxs_args[0]) - 1
+#define	LINUX_AL_SIZE	(nitems(lxs_args) - 1)
 
 int
 linux_socketcall(struct thread *td, struct linux_socketcall_args *args)
diff --git a/sys/ddb/db_variables.c b/sys/ddb/db_variables.c
index bd62db52f3cf..f48897adf147 100644
--- a/sys/ddb/db_variables.c
+++ b/sys/ddb/db_variables.c
@@ -54,7 +54,7 @@ static struct db_variable db_vars[] = {
 #endif
 };
 static struct db_variable *db_evars =
-	db_vars + sizeof(db_vars)/sizeof(db_vars[0]);
+	db_vars + nitems(db_vars);
 
 static int
 db_find_variable(struct db_variable **varp)
diff --git a/sys/fs/autofs/autofs.c b/sys/fs/autofs/autofs.c
index eee74ea43fa0..e339c80c196c 100644
--- a/sys/fs/autofs/autofs.c
+++ b/sys/fs/autofs/autofs.c
@@ -354,7 +354,7 @@ autofs_set_sigmask(sigset_t *oldset)
 	/* Remove the autofs set of signals from newset */
 	PROC_LOCK(curproc);
 	mtx_lock(&curproc->p_sigacts->ps_mtx);
-	for (i = 0 ; i < sizeof(autofs_sig_set)/sizeof(int) ; i++) {
+	for (i = 0 ; i < nitems(autofs_sig_set); i++) {
 		/*
 		 * But make sure we leave the ones already masked
 		 * by the process, i.e. remove the signal from the
diff --git a/sys/fs/nfs/nfs_commonkrpc.c b/sys/fs/nfs/nfs_commonkrpc.c
index c1d50f4cfb2d..1a50ec8685fa 100644
--- a/sys/fs/nfs/nfs_commonkrpc.c
+++ b/sys/fs/nfs/nfs_commonkrpc.c
@@ -1053,7 +1053,7 @@ nfs_sig_pending(sigset_t set)
 {
 	int i;
 	
-	for (i = 0 ; i < sizeof(newnfs_sig_set)/sizeof(int) ; i++)
+	for (i = 0 ; i < nitems(newnfs_sig_set); i++)
 		if (SIGISMEMBER(set, newnfs_sig_set[i]))
 			return (1);
 	return (0);
@@ -1078,7 +1078,7 @@ newnfs_set_sigmask(struct thread *td, sigset_t *oldset)
 	/* Remove the NFS set of signals from newset */
 	PROC_LOCK(p);
 	mtx_lock(&p->p_sigacts->ps_mtx);
-	for (i = 0 ; i < sizeof(newnfs_sig_set)/sizeof(int) ; i++) {
+	for (i = 0 ; i < nitems(newnfs_sig_set); i++) {
 		/*
 		 * But make sure we leave the ones already masked
 		 * by the process, ie. remove the signal from the
diff --git a/sys/geom/part/g_part_bsd.c b/sys/geom/part/g_part_bsd.c
index 5a5eabd31937..eaa5394b7c7c 100644
--- a/sys/geom/part/g_part_bsd.c
+++ b/sys/geom/part/g_part_bsd.c
@@ -141,7 +141,7 @@ bsd_parse_type(const char *type, uint8_t *fstype)
 		return (0);
 	}
 	for (i = 0;
-	    i < sizeof(bsd_alias_match) / sizeof(bsd_alias_match[0]); i++) {
+	    i < nitems(bsd_alias_match); i++) {
 		alias = g_part_alias_name(bsd_alias_match[i].alias);
 		if (strcasecmp(type, alias) == 0) {
 			*fstype = bsd_alias_match[i].type;
diff --git a/sys/geom/part/g_part_ebr.c b/sys/geom/part/g_part_ebr.c
index dfeda58538f3..e3e7e8f63db0 100644
--- a/sys/geom/part/g_part_ebr.c
+++ b/sys/geom/part/g_part_ebr.c
@@ -189,7 +189,7 @@ ebr_parse_type(const char *type, u_char *dp_typ)
 		return (0);
 	}
 	for (i = 0;
-	    i < sizeof(ebr_alias_match) / sizeof(ebr_alias_match[0]); i++) {
+	    i < nitems(ebr_alias_match); i++) {
 		alias = g_part_alias_name(ebr_alias_match[i].alias);
 		if (strcasecmp(type, alias) == 0) {
 			*dp_typ = ebr_alias_match[i].typ;
@@ -604,7 +604,7 @@ g_part_ebr_type(struct g_part_table *basetable, struct g_part_entry *baseentry,
 
 	entry = (struct g_part_ebr_entry *)baseentry;
 	for (i = 0;
-	    i < sizeof(ebr_alias_match) / sizeof(ebr_alias_match[0]); i++) {
+	    i < nitems(ebr_alias_match); i++) {
 		if (ebr_alias_match[i].typ == entry->ent.dp_typ)
 			return (g_part_alias_name(ebr_alias_match[i].alias));
 	}
diff --git a/sys/geom/part/g_part_ldm.c b/sys/geom/part/g_part_ldm.c
index 82bf76dad522..fec8e7716d41 100644
--- a/sys/geom/part/g_part_ldm.c
+++ b/sys/geom/part/g_part_ldm.c
@@ -454,7 +454,7 @@ ldm_privhdr_check(struct ldm_db *db, struct g_consumer *cp, int is_gpt)
 	} else
 		last = pp->mediasize / pp->sectorsize - 1;
 	for (found = 0, i = is_gpt;
-	    i < sizeof(ldm_ph_off) / sizeof(ldm_ph_off[0]); i++) {
+	    i < nitems(ldm_ph_off); i++) {
 		offset = ldm_ph_off[i];
 		/*
 		 * In the GPT case consumer is attached to the LDM metadata
@@ -1469,7 +1469,7 @@ g_part_ldm_type(struct g_part_table *basetable, struct g_part_entry *baseentry,
 
 	entry = (struct g_part_ldm_entry *)baseentry;
 	for (i = 0;
-	    i < sizeof(ldm_alias_match) / sizeof(ldm_alias_match[0]); i++) {
+	    i < nitems(ldm_alias_match); i++) {
 		if (ldm_alias_match[i].typ == entry->type)
 			return (g_part_alias_name(ldm_alias_match[i].alias));
 	}
diff --git a/sys/geom/part/g_part_mbr.c b/sys/geom/part/g_part_mbr.c
index c340106ccb40..1bb9702a9ec6 100644
--- a/sys/geom/part/g_part_mbr.c
+++ b/sys/geom/part/g_part_mbr.c
@@ -159,7 +159,7 @@ mbr_parse_type(const char *type, u_char *dp_typ)
 		return (0);
 	}
 	for (i = 0;
-	    i < sizeof(mbr_alias_match) / sizeof(mbr_alias_match[0]); i++) {
+	    i < nitems(mbr_alias_match); i++) {
 		alias = g_part_alias_name(mbr_alias_match[i].alias);
 		if (strcasecmp(type, alias) == 0) {
 			*dp_typ = mbr_alias_match[i].typ;
@@ -561,7 +561,7 @@ g_part_mbr_type(struct g_part_table *basetable, struct g_part_entry *baseentry,
 
 	entry = (struct g_part_mbr_entry *)baseentry;
 	for (i = 0;
-	    i < sizeof(mbr_alias_match) / sizeof(mbr_alias_match[0]); i++) {
+	    i < nitems(mbr_alias_match); i++) {
 		if (mbr_alias_match[i].typ == entry->ent.dp_typ)
 			return (g_part_alias_name(mbr_alias_match[i].alias));
 	}
diff --git a/sys/kern/kern_dump.c b/sys/kern/kern_dump.c
index e3d338fd4e29..8e922a1e1bd7 100644
--- a/sys/kern/kern_dump.c
+++ b/sys/kern/kern_dump.c
@@ -71,7 +71,7 @@ dumpsys_gen_pa_init(void)
 	int n, idx;
 
 	bzero(dump_map, sizeof(dump_map));
-	for (n = 0; n < sizeof(dump_map) / sizeof(dump_map[0]); n++) {
+	for (n = 0; n < nitems(dump_map); n++) {
 		idx = n * 2;
 		if (dump_avail[idx] == 0 && dump_avail[idx + 1] == 0)
 			break;
diff --git a/sys/kern/kern_ffclock.c b/sys/kern/kern_ffclock.c
index c168325b263c..d9101e8eeda4 100644
--- a/sys/kern/kern_ffclock.c
+++ b/sys/kern/kern_ffclock.c
@@ -160,7 +160,7 @@ SYSCTL_NODE(_kern_sysclock, OID_AUTO, ffclock, CTLFLAG_RW, 0,
 
 static char *sysclocks[] = {"feedback", "feed-forward"};
 #define	MAX_SYSCLOCK_NAME_LEN 16
-#define	NUM_SYSCLOCKS (sizeof(sysclocks) / sizeof(*sysclocks))
+#define	NUM_SYSCLOCKS nitems(sysclocks)
 
 static int ffclock_version = 2;
 SYSCTL_INT(_kern_sysclock_ffclock, OID_AUTO, version, CTLFLAG_RD,
diff --git a/sys/kern/kern_jail.c b/sys/kern/kern_jail.c
index 6189d8ca6623..3e4f79833fc2 100644
--- a/sys/kern/kern_jail.c
+++ b/sys/kern/kern_jail.c
@@ -357,8 +357,7 @@ sys_jail(struct thread *td, struct jail_args *uap)
 int
 kern_jail(struct thread *td, struct jail *j)
 {
-	struct iovec optiov[2 * (4
-			    + sizeof(pr_allow_names) / sizeof(pr_allow_names[0])
+	struct iovec optiov[2 * (4 + nitems(pr_allow_names)
 #ifdef INET
 			    + 1
 #endif
@@ -389,8 +388,7 @@ kern_jail(struct thread *td, struct jail *j)
 
 	/* Set permissions for top-level jails from sysctls. */
 	if (!jailed(td->td_ucred)) {
-		for (fi = 0; fi < sizeof(pr_allow_names) /
-		     sizeof(pr_allow_names[0]); fi++) {
+		for (fi = 0; fi < nitems(pr_allow_names); fi++) {
 			optiov[opt.uio_iovcnt].iov_base =
 			    (jail_default_allow & (1 << fi))
 			    ? pr_allow_names[fi] : pr_allow_nonames[fi];
@@ -503,8 +501,8 @@ kern_jail(struct thread *td, struct jail *j)
 	}
 	opt.uio_iovcnt++;
 #endif
-	KASSERT(opt.uio_iovcnt <= sizeof(optiov) / sizeof(optiov[0]),
-	    ("kern_jail: too many iovecs (%d)", opt.uio_iovcnt));
+	KASSERT(opt.uio_iovcnt <= nitems(optiov),
+		("kern_jail: too many iovecs (%d)", opt.uio_iovcnt));
 	error = kern_jail_set(td, &opt, JAIL_CREATE | JAIL_ATTACH);
 	free(u_path, M_TEMP);
 	return (error);
@@ -651,16 +649,14 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
 		gotrsnum = 1;
 
 	pr_flags = ch_flags = 0;
-	for (fi = 0; fi < sizeof(pr_flag_names) / sizeof(pr_flag_names[0]);
-	    fi++) {
+	for (fi = 0; fi < nitems(pr_flag_names); fi++) {
 		if (pr_flag_names[fi] == NULL)
 			continue;
 		vfs_flagopt(opts, pr_flag_names[fi], &pr_flags, 1 << fi);
 		vfs_flagopt(opts, pr_flag_nonames[fi], &ch_flags, 1 << fi);
 	}
 	ch_flags |= pr_flags;
-	for (fi = 0; fi < sizeof(pr_flag_jailsys) / sizeof(pr_flag_jailsys[0]);
-	    fi++) {
+	for (fi = 0; fi < nitems(pr_flag_jailsys); fi++) {
 		error = vfs_copyopt(opts, pr_flag_jailsys[fi].name, &jsys,
 		    sizeof(jsys));
 		if (error == ENOENT)
@@ -716,8 +712,7 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags)
 #endif
 
 	pr_allow = ch_allow = 0;
-	for (fi = 0; fi < sizeof(pr_allow_names) / sizeof(pr_allow_names[0]);
-	    fi++) {
+	for (fi = 0; fi < nitems(pr_allow_names); fi++) {
 		vfs_flagopt(opts, pr_allow_names[fi], &pr_allow, 1 << fi);
 		vfs_flagopt(opts, pr_allow_nonames[fi], &ch_allow, 1 << fi);
 	}
@@ -2136,8 +2131,7 @@ kern_jail_get(struct thread *td, struct uio *optuio, int flags)
 	    sizeof(pr->pr_devfs_rsnum));
 	if (error != 0 && error != ENOENT)
 		goto done_deref;
-	for (fi = 0; fi < sizeof(pr_flag_names) / sizeof(pr_flag_names[0]);
-	    fi++) {
+	for (fi = 0; fi < nitems(pr_flag_names); fi++) {
 		if (pr_flag_names[fi] == NULL)
 			continue;
 		i = (pr->pr_flags & (1 << fi)) ? 1 : 0;
@@ -2149,8 +2143,7 @@ kern_jail_get(struct thread *td, struct uio *optuio, int flags)
 		if (error != 0 && error != ENOENT)
 			goto done_deref;
 	}
-	for (fi = 0; fi < sizeof(pr_flag_jailsys) / sizeof(pr_flag_jailsys[0]);
-	    fi++) {
+	for (fi = 0; fi < nitems(pr_flag_jailsys); fi++) {
 		i = pr->pr_flags &
 		    (pr_flag_jailsys[fi].disable | pr_flag_jailsys[fi].new);
 		i = pr_flag_jailsys[fi].disable &&
@@ -2162,8 +2155,7 @@ kern_jail_get(struct thread *td, struct uio *optuio, int flags)
 		if (error != 0 && error != ENOENT)
 			goto done_deref;
 	}
-	for (fi = 0; fi < sizeof(pr_allow_names) / sizeof(pr_allow_names[0]);
-	    fi++) {
+	for (fi = 0; fi < nitems(pr_allow_names); fi++) {
 		if (pr_allow_names[fi] == NULL)
 			continue;
 		i = (pr->pr_allow & (1 << fi)) ? 1 : 0;
@@ -4694,12 +4686,10 @@ db_show_prison(struct prison *pr)
 	db_printf(" child           = %p\n", LIST_FIRST(&pr->pr_children));
 	db_printf(" sibling         = %p\n", LIST_NEXT(pr, pr_sibling));
 	db_printf(" flags           = 0x%x", pr->pr_flags);
-	for (fi = 0; fi < sizeof(pr_flag_names) / sizeof(pr_flag_names[0]);
-	    fi++)
+	for (fi = 0; fi < nitems(pr_flag_names); fi++)
 		if (pr_flag_names[fi] != NULL && (pr->pr_flags & (1 << fi)))
 			db_printf(" %s", pr_flag_names[fi]);
-	for (fi = 0; fi < sizeof(pr_flag_jailsys) / sizeof(pr_flag_jailsys[0]);
-	    fi++) {
+	for (fi = 0; fi < nitems(pr_flag_jailsys); fi++) {
 		jsf = pr->pr_flags &
 		    (pr_flag_jailsys[fi].disable | pr_flag_jailsys[fi].new);
 		db_printf(" %-16s= %s\n", pr_flag_jailsys[fi].name,
@@ -4709,8 +4699,7 @@ db_show_prison(struct prison *pr)
 		    : "inherit");
 	}
 	db_printf(" allow           = 0x%x", pr->pr_allow);
-	for (fi = 0; fi < sizeof(pr_allow_names) / sizeof(pr_allow_names[0]);
-	    fi++)
+	for (fi = 0; fi < nitems(pr_allow_names); fi++)
 		if (pr_allow_names[fi] != NULL && (pr->pr_allow & (1 << fi)))
 			db_printf(" %s", pr_allow_names[fi]);
 	db_printf("\n");
diff --git a/sys/kern/kern_ktrace.c b/sys/kern/kern_ktrace.c
index 139fd31a9ac0..0e30fc9cd9c8 100644
--- a/sys/kern/kern_ktrace.c
+++ b/sys/kern/kern_ktrace.c
@@ -1163,8 +1163,7 @@ ktr_writerequest(struct thread *td, struct ktr_request *req)
 	mtx_unlock(&ktrace_mtx);
 
 	kth = &req->ktr_header;
-	KASSERT(((u_short)kth->ktr_type & ~KTR_DROP) <
-	    sizeof(data_lengths) / sizeof(data_lengths[0]),
+	KASSERT(((u_short)kth->ktr_type & ~KTR_DROP) < nitems(data_lengths),
 	    ("data_lengths array overflow"));
 	datalen = data_lengths[(u_short)kth->ktr_type & ~KTR_DROP];
 	buflen = kth->ktr_len;
diff --git a/sys/kern/subr_hash.c b/sys/kern/subr_hash.c
index fe8128691596..915f3f7bfe05 100644
--- a/sys/kern/subr_hash.c
+++ b/sys/kern/subr_hash.c
@@ -101,7 +101,7 @@ hashdestroy(void *vhashtbl, struct malloc_type *type, u_long hashmask)
 static const int primes[] = { 1, 13, 31, 61, 127, 251, 509, 761, 1021, 1531,
 			2039, 2557, 3067, 3583, 4093, 4603, 5119, 5623, 6143,
 			6653, 7159, 7673, 8191, 12281, 16381, 24571, 32749 };
-#define NPRIMES (sizeof(primes) / sizeof(primes[0]))
+#define	NPRIMES nitems(primes)
 
 /*
  * General routine to allocate a prime number sized hash table.
diff --git a/sys/kern/subr_witness.c b/sys/kern/subr_witness.c
index 5ca1eb9814c6..29c83c0c4311 100644
--- a/sys/kern/subr_witness.c
+++ b/sys/kern/subr_witness.c
@@ -709,8 +709,7 @@ static struct witness_order_list_entry order_lists[] = {
  */
 static struct witness_blessed blessed_list[] = {
 };
-static int blessed_count =
-	sizeof(blessed_list) / sizeof(struct witness_blessed);
+static int blessed_count = nitems(blessed_list);
 #endif
 
 /*
diff --git a/sys/kern/sysv_msg.c b/sys/kern/sysv_msg.c
index 59357c492240..22845bb53d88 100644
--- a/sys/kern/sysv_msg.c
+++ b/sys/kern/sysv_msg.c
@@ -1519,7 +1519,7 @@ sys_msgsys(td, uap)
 	if (!prison_allow(td->td_ucred, PR_ALLOW_SYSVIPC))
 		return (ENOSYS);
 	if (uap->which < 0 ||
-	    uap->which >= sizeof(msgcalls)/sizeof(msgcalls[0]))
+	    uap->which >= nitems(msgcalls))
 		return (EINVAL);
 	error = (*msgcalls[uap->which])(td, &uap->a2);
 	return (error);
diff --git a/sys/kern/sysv_sem.c b/sys/kern/sysv_sem.c
index 0063916c5194..d3546a186430 100644
--- a/sys/kern/sysv_sem.c
+++ b/sys/kern/sysv_sem.c
@@ -1401,7 +1401,7 @@ sys_semsys(td, uap)
 	if (!prison_allow(td->td_ucred, PR_ALLOW_SYSVIPC))
 		return (ENOSYS);
 	if (uap->which < 0 ||
-	    uap->which >= sizeof(semcalls)/sizeof(semcalls[0]))
+	    uap->which >= nitems(semcalls))
 		return (EINVAL);
 	error = (*semcalls[uap->which])(td, &uap->a2);
 	return (error);
diff --git a/sys/kern/uipc_usrreq.c b/sys/kern/uipc_usrreq.c
index 4e5aa88a61c0..f0d282cebd7c 100644
--- a/sys/kern/uipc_usrreq.c
+++ b/sys/kern/uipc_usrreq.c
@@ -337,7 +337,7 @@ static struct domain localdomain = {
 	.dom_externalize =	unp_externalize,
 	.dom_dispose =		unp_dispose_so,
 	.dom_protosw =		localsw,
-	.dom_protoswNPROTOSW =	&localsw[sizeof(localsw)/sizeof(localsw[0])]
+	.dom_protoswNPROTOSW =	&localsw[nitems(localsw)]
 };
 DOMAIN_SET(local);
 
diff --git a/sys/net/rtsock.c b/sys/net/rtsock.c
index 810da1bad031..4a229136c1d2 100644
--- a/sys/net/rtsock.c
+++ b/sys/net/rtsock.c
@@ -1919,7 +1919,7 @@ static struct domain routedomain = {
 	.dom_family =		PF_ROUTE,
 	.dom_name =		 "route",
 	.dom_protosw =		routesw,
-	.dom_protoswNPROTOSW =	&routesw[sizeof(routesw)/sizeof(routesw[0])]
+	.dom_protoswNPROTOSW =	&routesw[nitems(routesw)]
 };
 
 VNET_DOMAIN_SET(route);
diff --git a/sys/netinet/in_proto.c b/sys/netinet/in_proto.c
index e7569c45f740..1d32caf42b90 100644
--- a/sys/netinet/in_proto.c
+++ b/sys/netinet/in_proto.c
@@ -357,7 +357,7 @@ struct domain inetdomain = {
 	.dom_family =		AF_INET,
 	.dom_name =		"internet",
 	.dom_protosw =		inetsw,
-	.dom_protoswNPROTOSW =	&inetsw[sizeof(inetsw)/sizeof(inetsw[0])],
+	.dom_protoswNPROTOSW =	&inetsw[nitems(inetsw)],
 #ifdef RADIX_MPATH
 	.dom_rtattach =		rn4_mpath_inithead,
 #else
diff --git a/sys/netinet/tcp_syncache.c b/sys/netinet/tcp_syncache.c
index 1cf27e1da923..91e4c5902570 100644
--- a/sys/netinet/tcp_syncache.c
+++ b/sys/netinet/tcp_syncache.c
@@ -1896,7 +1896,7 @@ syncookie_generate(struct syncache_head *sch, struct syncache *sc)
 
 	/* Map our computed MSS into the 3-bit index. */
 	mss = min(tcp_mssopt(&sc->sc_inc), max(sc->sc_peer_mss, V_tcp_minmss));
-	for (i = sizeof(tcp_sc_msstab) / sizeof(*tcp_sc_msstab) - 1;
+	for (i = nitems(tcp_sc_msstab) - 1;
 	     tcp_sc_msstab[i] > mss && i > 0;
 	     i--)
 		;
@@ -1908,7 +1908,7 @@ syncookie_generate(struct syncache_head *sch, struct syncache *sc)
 	 */
 	if (sc->sc_flags & SCF_WINSCALE) {
 		wscale = sc->sc_requested_s_scale;
-		for (i = sizeof(tcp_sc_wstab) / sizeof(*tcp_sc_wstab) - 1;
+		for (i = nitems(tcp_sc_wstab) - 1;
 		     tcp_sc_wstab[i] > wscale && i > 0;
 		     i--)
 			;
diff --git a/sys/netinet6/in6_proto.c b/sys/netinet6/in6_proto.c
index cad09316cf94..68cb8fd7bdad 100644
--- a/sys/netinet6/in6_proto.c
+++ b/sys/netinet6/in6_proto.c
@@ -382,7 +382,7 @@ struct domain inet6domain = {
 	.dom_name =		"internet6",
 	.dom_protosw =		(struct protosw *)inet6sw,
 	.dom_protoswNPROTOSW =	(struct protosw *)
-				&inet6sw[sizeof(inet6sw)/sizeof(inet6sw[0])],
+				&inet6sw[nitems(inet6sw)],
 #ifdef RADIX_MPATH
 	.dom_rtattach =		rn6_mpath_inithead,
 #else
diff --git a/sys/netipsec/key.c b/sys/netipsec/key.c
index 7070c1df4510..4e8c633c7a18 100644
--- a/sys/netipsec/key.c
+++ b/sys/netipsec/key.c
@@ -3365,7 +3365,7 @@ key_setdumpsa(struct secasvar *sav, u_int8_t type, u_int8_t satype,
 		goto fail;
 	result = m;
 
-	for (i = sizeof(dumporder)/sizeof(dumporder[0]) - 1; i >= 0; i--) {
+	for (i = nitems(dumporder) - 1; i >= 0; i--) {
 		m = NULL;
 		switch (dumporder[i]) {
 		case SADB_EXT_SA:
@@ -7410,7 +7410,7 @@ key_parse(struct mbuf *m, struct socket *so)
 		 */
 	}
 
-	if (msg->sadb_msg_type >= sizeof(key_typesw)/sizeof(key_typesw[0]) ||
+	if (msg->sadb_msg_type >= nitems(key_typesw) ||
 	    key_typesw[msg->sadb_msg_type] == NULL) {
 		PFKEYSTAT_INC(out_invmsgtype);
 		error = EINVAL;
@@ -7562,8 +7562,8 @@ key_validate_ext(const struct sadb_ext *ext, int len)
 		return EINVAL;
 
 	/* if it does not match minimum/maximum length, bail */
-	if (ext->sadb_ext_type >= sizeof(minsize) / sizeof(minsize[0]) ||
-	    ext->sadb_ext_type >= sizeof(maxsize) / sizeof(maxsize[0]))
+	if (ext->sadb_ext_type >= nitems(minsize) ||
+	    ext->sadb_ext_type >= nitems(maxsize))
 		return EINVAL;
 	if (!minsize[ext->sadb_ext_type] || len < minsize[ext->sadb_ext_type])
 		return EINVAL;
diff --git a/sys/netipsec/keysock.c b/sys/netipsec/keysock.c
index 73e54bb3de32..c3092e42f685 100644
--- a/sys/netipsec/keysock.c
+++ b/sys/netipsec/keysock.c
@@ -564,7 +564,7 @@ struct domain keydomain = {
 	.dom_destroy =		key_destroy,
 #endif
 	.dom_protosw =		keysw,
-	.dom_protoswNPROTOSW =	&keysw[sizeof(keysw)/sizeof(keysw[0])]
+	.dom_protoswNPROTOSW =	&keysw[nitems(keysw)]
 };
 
 VNET_DOMAIN_SET(key);
diff --git a/sys/netnatm/natm_proto.c b/sys/netnatm/natm_proto.c
index b064c4340017..aa7fa2cd8511 100644
--- a/sys/netnatm/natm_proto.c
+++ b/sys/netnatm/natm_proto.c
@@ -87,7 +87,7 @@ static struct domain natmdomain = {
 	.dom_name =		"natm",
 	.dom_init =		natm_init,
 	.dom_protosw =		natmsw,
-	.dom_protoswNPROTOSW =	&natmsw[sizeof(natmsw)/sizeof(natmsw[0])],
+	.dom_protoswNPROTOSW =	&natmsw[nitems(natmsw)],
 };
 
 static struct netisr_handler natm_nh = {
diff --git a/sys/netsmb/smb_smb.c b/sys/netsmb/smb_smb.c
index 6c732f9d4043..6d4f3898e1c3 100644
--- a/sys/netsmb/smb_smb.c
+++ b/sys/netsmb/smb_smb.c
@@ -68,7 +68,7 @@ static struct smb_dialect smb_dialects[] = {
 	{-1,			NULL}
 };
 
-#define	SMB_DIALECT_MAX	(sizeof(smb_dialects) / sizeof(struct smb_dialect) - 2)
+#define	SMB_DIALECT_MAX	(nitems(smb_dialects) - 2)
 
 static u_int32_t
 smb_vc_maxread(struct smb_vc *vcp)