diff --git a/libcxx/include/charconv b/libcxx/include/charconv
--- a/libcxx/include/charconv
+++ b/libcxx/include/charconv
@@ -108,6 +108,49 @@
     general = fixed | scientific
 };
 
+using __chars_format_underlying_type = underlying_type<chars_format>::type;
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR chars_format
+operator~(chars_format __x) {
+  return chars_format(~static_cast<__chars_format_underlying_type>(__x) & 0x7);
+}
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR chars_format
+operator&(chars_format __x, chars_format __y) {
+  return chars_format(static_cast<__chars_format_underlying_type>(__x) &
+                      static_cast<__chars_format_underlying_type>(__y));
+}
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR chars_format
+operator|(chars_format __x, chars_format __y) {
+  return chars_format(static_cast<__chars_format_underlying_type>(__x) |
+                      static_cast<__chars_format_underlying_type>(__y));
+}
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR chars_format
+operator^(chars_format __x, chars_format __y) {
+  return chars_format(static_cast<__chars_format_underlying_type>(__x) ^
+                      static_cast<__chars_format_underlying_type>(__y));
+}
+
+inline _LIBCPP_INLINE_VISIBILITY chars_format& operator&=(chars_format& __x,
+                                                          chars_format __y) {
+  __x = __x & __y;
+  return __x;
+}
+
+inline _LIBCPP_INLINE_VISIBILITY chars_format& operator|=(chars_format& __x,
+                                                          chars_format __y) {
+  __x = __x | __y;
+  return __x;
+}
+
+inline _LIBCPP_INLINE_VISIBILITY chars_format& operator^=(chars_format& __x,
+                                                          chars_format __y) {
+  __x = __x ^ __y;
+  return __x;
+}
+
 struct _LIBCPP_TYPE_VIS to_chars_result
 {
     char* ptr;
diff --git a/libcxx/test/std/utilities/charconv/charconv.syn/chars_format.pass.cpp b/libcxx/test/std/utilities/charconv/charconv.syn/chars_format.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/utilities/charconv/charconv.syn/chars_format.pass.cpp
@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03
+
+// <charconv>
+
+// Bitmask type
+// enum class chars_format {
+//   scientific = unspecified,
+//   fixed = unspecified,
+//   hex = unspecified,
+//   general = fixed | scientific
+// };
+
+#include <charconv>
+#include <cassert>
+
+#include "test_macros.h"
+
+void test() {
+  {
+    std::chars_format x = std::chars_format::scientific;
+    x |= std::chars_format::fixed;
+    assert(x == std::chars_format::general);
+  }
+
+  {
+    std::chars_format x = std::chars_format::general;
+    x &= std::chars_format::fixed;
+    assert(x == std::chars_format::fixed);
+  }
+  {
+    std::chars_format x = std::chars_format::general;
+    x ^= std::chars_format::fixed;
+    assert(x == std::chars_format::scientific);
+  }
+}
+
+constexpr bool test_constexpr() {
+  // This construction is used to make the function constexpr in C++11.
+  return (static_cast<std::__chars_format_underlying_type>(
+              std::chars_format::scientific) == 1) &&
+         (static_cast<std::__chars_format_underlying_type>(
+              std::chars_format::fixed) == 2) &&
+         (static_cast<std::__chars_format_underlying_type>(
+              std::chars_format::hex) == 4) &&
+
+         ((std::chars_format::scientific | std::chars_format::fixed) ==
+          std::chars_format::general) &&
+
+         (static_cast<std::__chars_format_underlying_type>(
+              std::chars_format::scientific & std::chars_format::fixed) == 0) &&
+
+         ((std::chars_format::general ^ std::chars_format::fixed) ==
+          std::chars_format::scientific) &&
+
+         (~std::chars_format::hex == std::chars_format::general);
+}
+
+int main(int, char**) {
+  test();
+  test_constexpr();
+  static_assert(test_constexpr(), "");
+
+  return 0;
+}