diff --git a/dlls/winhttp/tests/notification.c b/dlls/winhttp/tests/notification.c
index 2a647e3633f..086f2e7935a 100644
--- a/dlls/winhttp/tests/notification.c
+++ b/dlls/winhttp/tests/notification.c
@@ -187,7 +187,7 @@ static void test_connection_cache( void )
     struct info info, *context = &info;
 
     info.test  = cache_test;
-    info.count = sizeof(cache_test) / sizeof(cache_test[0]);
+    info.count = ARRAY_SIZE( cache_test );
     info.index = 0;
     info.wait = CreateEventW( NULL, FALSE, FALSE, NULL );
 
@@ -427,7 +427,7 @@ static void test_redirect( void )
     struct info info, *context = &info;
 
     info.test  = redirect_test;
-    info.count = sizeof(redirect_test) / sizeof(redirect_test[0]);
+    info.count = ARRAY_SIZE( redirect_test );
     info.index = 0;
     info.wait = CreateEventW( NULL, FALSE, FALSE, NULL );
 
@@ -508,7 +508,7 @@ static void test_async( void )
     char buffer[1024];
 
     info.test  = async_test;
-    info.count = sizeof(async_test) / sizeof(async_test[0]);
+    info.count = ARRAY_SIZE( async_test );
     info.index = 0;
     info.wait = CreateEventW( NULL, FALSE, FALSE, NULL );
 
@@ -779,12 +779,12 @@ static void open_async_request(int port, struct test_request *req, struct info *
     if (reuse_connection)
     {
         info->test  = reuse_socket_request_test;
-        info->count = sizeof(reuse_socket_request_test) / sizeof(reuse_socket_request_test[0]);
+        info->count = ARRAY_SIZE( reuse_socket_request_test );
     }
     else
     {
         info->test  = open_socket_request_test;
-        info->count = sizeof(open_socket_request_test) / sizeof(open_socket_request_test[0]);
+        info->count = ARRAY_SIZE( open_socket_request_test );
     }
 
     req->session = WinHttpOpen( user_agent, 0, NULL, NULL, WINHTTP_FLAG_ASYNC );
@@ -830,7 +830,7 @@ static void server_send_reply(struct test_request *req, struct info *info, const
     WaitForSingleObject( info->wait, INFINITE );
 
     info->test  = server_reply_test;
-    info->count = sizeof(server_reply_test) / sizeof(server_reply_test[0]);
+    info->count = ARRAY_SIZE( server_reply_test );
     info->index = 0;
     setup_test( info, winhttp_send_request, __LINE__ );
     ret = WinHttpReceiveResponse( req->request, NULL );
@@ -879,12 +879,12 @@ static void close_request(struct test_request *req, struct info *info, BOOL allo
     if (allow_closing_connection)
     {
         info->test = close_allow_connection_close_request_test;
-        info->count = sizeof(close_allow_connection_close_request_test)/sizeof(*close_allow_connection_close_request_test);
+        info->count = ARRAY_SIZE( close_allow_connection_close_request_test );
     }
     else
     {
         info->test = close_request_test;
-        info->count = sizeof(close_request_test)/sizeof(*close_request_test);
+        info->count = ARRAY_SIZE( close_request_test );
     }
     info->index = 0;
     setup_test( info, winhttp_close_handle, __LINE__ );
@@ -926,12 +926,12 @@ static void _read_request_data(struct test_request *req, struct info *info, cons
     if (closing_connection)
     {
         info->test = read_allow_close_test;
-        info->count = sizeof(read_allow_close_test)/sizeof(*read_allow_close_test);
+        info->count = ARRAY_SIZE( read_allow_close_test );
     }
     else
     {
         info->test = read_test;
-        info->count = sizeof(read_test)/sizeof(*read_test);
+        info->count = ARRAY_SIZE( read_test );
     }
     info->index = 0;
 
diff --git a/dlls/winhttp/tests/winhttp.c b/dlls/winhttp/tests/winhttp.c
index 4b4a84c5fc7..46504e1b0cf 100644
--- a/dlls/winhttp/tests/winhttp.c
+++ b/dlls/winhttp/tests/winhttp.c
@@ -2907,7 +2907,7 @@ static void test_not_modified(int port)
 
     memcpy(today, ifmodifiedW, sizeof(ifmodifiedW));
     GetSystemTime(&st);
-    WinHttpTimeFromSystemTime(&st, &today[sizeof(ifmodifiedW)/sizeof(WCHAR)]);
+    WinHttpTimeFromSystemTime(&st, &today[ARRAY_SIZE(ifmodifiedW)]);
 
     session = WinHttpOpen(test_useragent, WINHTTP_ACCESS_TYPE_NO_PROXY,
         WINHTTP_NO_PROXY_NAME, WINHTTP_NO_PROXY_BYPASS, 0);
@@ -3277,13 +3277,13 @@ static void test_credentials(void)
     req = WinHttpOpenRequest(con, NULL, NULL, NULL, NULL, NULL, 0);
     ok(req != NULL, "failed to open a request %u\n", GetLastError());
 
-    size = sizeof(buffer)/sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = WinHttpQueryOption(req, WINHTTP_OPTION_PROXY_USERNAME, &buffer, &size);
     ok(ret, "failed to query proxy username %u\n", GetLastError());
     ok(!buffer[0], "unexpected result %s\n", wine_dbgstr_w(buffer));
     ok(!size, "expected 0, got %u\n", size);
 
-    size = sizeof(buffer)/sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = WinHttpQueryOption(req, WINHTTP_OPTION_PROXY_PASSWORD, &buffer, &size);
     ok(ret, "failed to query proxy password %u\n", GetLastError());
     ok(!buffer[0], "unexpected result %s\n", wine_dbgstr_w(buffer));
@@ -3292,19 +3292,19 @@ static void test_credentials(void)
     ret = WinHttpSetOption(req, WINHTTP_OPTION_PROXY_USERNAME, proxy_userW, lstrlenW(proxy_userW));
     ok(ret, "failed to set username %u\n", GetLastError());
 
-    size = sizeof(buffer)/sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = WinHttpQueryOption(req, WINHTTP_OPTION_PROXY_USERNAME, &buffer, &size);
     ok(ret, "failed to query proxy username %u\n", GetLastError());
     ok(!winetest_strcmpW(buffer, proxy_userW), "unexpected result %s\n", wine_dbgstr_w(buffer));
     ok(size == lstrlenW(proxy_userW) * sizeof(WCHAR), "unexpected result %u\n", size);
 
-    size = sizeof(buffer)/sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = WinHttpQueryOption(req, WINHTTP_OPTION_USERNAME, &buffer, &size);
     ok(ret, "failed to query username %u\n", GetLastError());
     ok(!buffer[0], "unexpected result %s\n", wine_dbgstr_w(buffer));
     ok(!size, "expected 0, got %u\n", size);
 
-    size = sizeof(buffer)/sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = WinHttpQueryOption(req, WINHTTP_OPTION_PASSWORD, &buffer, &size);
     ok(ret, "failed to query password %u\n", GetLastError());
     ok(!buffer[0], "unexpected result %s\n", wine_dbgstr_w(buffer));
@@ -3313,7 +3313,7 @@ static void test_credentials(void)
     ret = WinHttpSetOption(req, WINHTTP_OPTION_PROXY_PASSWORD, proxy_passW, lstrlenW(proxy_passW));
     ok(ret, "failed to set proxy password %u\n", GetLastError());
 
-    size = sizeof(buffer)/sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = WinHttpQueryOption(req, WINHTTP_OPTION_PROXY_PASSWORD, &buffer, &size);
     ok(ret, "failed to query proxy password %u\n", GetLastError());
     ok(!winetest_strcmpW(buffer, proxy_passW), "unexpected result %s\n", wine_dbgstr_w(buffer));
@@ -3322,7 +3322,7 @@ static void test_credentials(void)
     ret = WinHttpSetOption(req, WINHTTP_OPTION_USERNAME, userW, lstrlenW(userW));
     ok(ret, "failed to set username %u\n", GetLastError());
 
-    size = sizeof(buffer)/sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = WinHttpQueryOption(req, WINHTTP_OPTION_USERNAME, &buffer, &size);
     ok(ret, "failed to query username %u\n", GetLastError());
     ok(!winetest_strcmpW(buffer, userW), "unexpected result %s\n", wine_dbgstr_w(buffer));
@@ -3331,7 +3331,7 @@ static void test_credentials(void)
     ret = WinHttpSetOption(req, WINHTTP_OPTION_PASSWORD, passW, lstrlenW(passW));
     ok(ret, "failed to set password %u\n", GetLastError());
 
-    size = sizeof(buffer)/sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = WinHttpQueryOption(req, WINHTTP_OPTION_PASSWORD, &buffer, &size);
     ok(ret, "failed to query password %u\n", GetLastError());
     ok(!winetest_strcmpW(buffer, passW), "unexpected result %s\n", wine_dbgstr_w(buffer));
@@ -3357,7 +3357,7 @@ static void test_credentials(void)
     ret = WinHttpSetCredentials(req, WINHTTP_AUTH_TARGET_SERVER, WINHTTP_AUTH_SCHEME_BASIC, userW, passW, NULL);
     ok(ret, "failed to set credentials %u\n", GetLastError());
 
-    size = sizeof(buffer)/sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = WinHttpQueryOption(req, WINHTTP_OPTION_USERNAME, &buffer, &size);
     ok(ret, "failed to query username %u\n", GetLastError());
     todo_wine {
@@ -3365,7 +3365,7 @@ static void test_credentials(void)
     ok(!size, "expected 0, got %u\n", size);
     }
 
-    size = sizeof(buffer)/sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = WinHttpQueryOption(req, WINHTTP_OPTION_PASSWORD, &buffer, &size);
     ok(ret, "failed to query password %u\n", GetLastError());
     todo_wine {
@@ -3920,7 +3920,7 @@ static void test_IWinHttpRequest(int port)
     ok( hr == S_OK, "got %08x\n", hr );
 
     sprintf( buf, "http://localhost:%d/auth", port );
-    MultiByteToWideChar( CP_ACP, 0, buf, -1, bufW, sizeof(bufW)/sizeof(bufW[0]) );
+    MultiByteToWideChar( CP_ACP, 0, buf, -1, bufW, ARRAY_SIZE( bufW ));
     url = SysAllocString( bufW );
     method = SysAllocString( method3W );
     V_VT( &async ) = VT_BOOL;