diff --git a/modules/rostests/apitests/crt/__64tof.c b/modules/rostests/apitests/crt/__64tof.c
new file mode 100644
index 00000000000..224df034699
--- /dev/null
+++ b/modules/rostests/apitests/crt/__64tof.c
@@ -0,0 +1,130 @@
+/*
+ * PROJECT:         ReactOS API tests
+ * LICENSE:         GPL-2.0-or-later (https://spdx.org/licenses/GPL-2.0-or-later)
+ * PURPOSE:         Tests for __i64tod/u64tod/i64tos/u64tos on ARM
+ * COPYRIGHT:       Copyright 2021 Stanislav Motylkov <x86corez@gmail.com>
+ */
+
+#include <apitest.h>
+
+typedef struct _I64TOD_TEST_DATA
+{
+    long long given;
+    union
+    {
+        double value;
+        unsigned long long raw;
+    } expected;
+} I64TOD_TEST_DATA;
+
+typedef struct _U64TOD_TEST_DATA
+{
+    unsigned long long given;
+    union
+    {
+        double value;
+        unsigned long long raw;
+    } expected;
+} U64TOD_TEST_DATA;
+
+typedef struct _I64TOS_TEST_DATA
+{
+    long long given;
+    union
+    {
+        float value;
+        unsigned int raw;
+    } expected;
+} I64TOS_TEST_DATA;
+
+typedef struct _U64TOS_TEST_DATA
+{
+    unsigned long long given;
+    union
+    {
+        float value;
+        unsigned int raw;
+    } expected;
+} U64TOS_TEST_DATA;
+
+START_TEST(__64tof)
+{
+    I64TOD_TEST_DATA i64tod[] =
+    {
+        { 1383034209LL, 1383034209.0 }, /* test 32bit number */
+        { -1383034209LL, -1383034209.0 }, /* test negative 32bit number */
+        { 354056757614LL, 354056757614.0 }, /* test 64bit int */
+        { -354056757614LL, -354056757614.0 }, /* test negative 64bit int */
+        { 18446744073709550000LL, -1616.0 }, /* test 20bit in float */
+        { 0x8000000000000000LL, -9223372036854775800.0 }, /* test big 64bit int */
+        { 0xFFFFFFFFFFFFFFFFLL, -1.0 }, /* test -1 */
+        { 0LL, +0.0 }, /* test 0 */
+    };
+    U64TOD_TEST_DATA u64tod[] =
+    {
+        { 1383034209ULL, 1383034209.0 }, /* test 32bit number */
+        { 354056757614ULL, 354056757614.0 }, /* test 64bit int */
+        { 18445937028656326656ULL, 18445937028656326656.0 }, /* test unsigned 64bit */
+        { 18446744073709550000ULL, 18446744073709550000.0 }, /* test 20bit in float */
+        { 18446744073709551615ULL, 18446744073709552000.0 }, /* test big 64bit number */
+        { 0ULL, +0.0 }, /* test 0 */
+    };
+    I64TOS_TEST_DATA i64tos[] =
+    {
+        { 1383034LL, 1383034.0f }, /* test 32bit number */
+        { -1383034LL, -1383034.0f }, /* test negative 32bit number */
+        { 354056765440LL, 354056765440.0f }, /* test 64bit int */
+        { -354056765440LL, -354056765440.0f }, /* test negative 64bit int */
+        { 18446744073709550000LL, -1616.0f }, /* test 20bit in float */
+        { 0x8000000000000000LL, -9223372036854775800.0f }, /* test big 64bit int */
+        { 0xFFFFFFFFFFFFFFFFLL, -1.0f }, /* test -1 */
+        { 0LL, +0.0f }, /* test 0 */
+    };
+    U64TOS_TEST_DATA u64tos[] =
+    {
+        { 1383034ULL, 1383034.0f }, /* test 32bit number */
+        { 354056765440ULL, 354056765440.0f }, /* test 64bit int */
+        { 18445937032174764032ULL, 18445937032174764032.0f }, /* test unsigned 64bit */
+        { 18446744073709550000ULL, 18446744073709550000.0f }, /* test 20bit in float */
+        { 18446744073709551615ULL, 18446744073709552000.0f }, /* test big 64bit number */
+        { 0ULL, +0.0f }, /* test 0 */
+    };
+
+    unsigned int i;
+
+    for (i = 0; i < _countof(i64tod); ++i)
+    {
+        double actual;
+
+        actual = (double)i64tod[i].given;
+        ok(actual == i64tod[i].expected.value, "(i64tod) %d: Expected %lf, but %lld -> %lf\n",
+           i, i64tod[i].expected.value, i64tod[i].given, actual);
+    }
+
+    for (i = 0; i < _countof(u64tod); ++i)
+    {
+        double actual;
+
+        actual = (double)u64tod[i].given;
+        ok(actual == u64tod[i].expected.value, "(u64tod) %d: Expected %lf, but %llu -> %lf\n",
+           i, u64tod[i].expected.value, u64tod[i].given, actual);
+    }
+
+    for (i = 0; i < _countof(i64tos); ++i)
+    {
+        float actual;
+
+        actual = (float)i64tos[i].given;
+        ok(actual == i64tos[i].expected.value, "(i64tos) %d: Expected %f, but %lld -> %f\n",
+           i, i64tos[i].expected.value, i64tos[i].given, actual);
+    }
+
+    for (i = 0; i < _countof(u64tos); ++i)
+    {
+        float actual;
+
+        actual = (float)u64tos[i].given;
+        ok(actual == u64tos[i].expected.value, "(u64tos) %d: Expected %f, but %llu -> %f\n",
+           i, u64tos[i].expected.value, u64tos[i].given, actual);
+    }
+}
diff --git a/modules/rostests/apitests/crt/msvcrt_crt_apitest.cmake b/modules/rostests/apitests/crt/msvcrt_crt_apitest.cmake
index dcef3b0d582..82283e5a3a6 100644
--- a/modules/rostests/apitests/crt/msvcrt_crt_apitest.cmake
+++ b/modules/rostests/apitests/crt/msvcrt_crt_apitest.cmake
@@ -1376,6 +1376,7 @@ elseif(ARCH STREQUAL "arm")
     list(APPEND SOURCE_MSVCRT
         __rt_div.c
         __fto64.c
+        __64tof.c
     )
 endif()
 
diff --git a/modules/rostests/apitests/crt/static_crt_apitest.cmake b/modules/rostests/apitests/crt/static_crt_apitest.cmake
index 17ff8f8d733..a3e35c412b3 100644
--- a/modules/rostests/apitests/crt/static_crt_apitest.cmake
+++ b/modules/rostests/apitests/crt/static_crt_apitest.cmake
@@ -30,6 +30,7 @@ elseif(ARCH STREQUAL "arm")
     list(APPEND SOURCE_STATIC
         __rt_div.c
         __fto64.c
+        __64tof.c
     )
 endif()
 
diff --git a/modules/rostests/apitests/crt/testlist.c b/modules/rostests/apitests/crt/testlist.c
index 1997603fbca..e8b4c7670fb 100644
--- a/modules/rostests/apitests/crt/testlist.c
+++ b/modules/rostests/apitests/crt/testlist.c
@@ -12,6 +12,7 @@ extern void func_atexit(void);
 #if defined(_M_ARM)
 extern void func___rt_div(void);
 extern void func___fto64(void);
+extern void func___64tof(void);
 #endif
 #endif
 #if defined(TEST_NTDLL)
@@ -62,6 +63,7 @@ const struct test winetest_testlist[] =
 #if defined(_M_ARM)
     { "__rt_div", func___rt_div },
     { "__fto64", func___fto64 },
+    { "__64tof", func___64tof },
 #endif
 #endif
 #if defined(TEST_STATIC_CRT)