diff --git a/src/string_util.h b/src/string_util.h
new file mode 100644
index 0000000..fc5f8b0
--- /dev/null
+++ b/src/string_util.h
@@ -0,0 +1,60 @@
+#ifndef BENCHMARK_STRING_UTIL_H_
+#define BENCHMARK_STRING_UTIL_H_
+
+#include <sstream>
+#include <string>
+#include <utility>
+#include "internal_macros.h"
+
+namespace benchmark {
+
+void AppendHumanReadable(int n, std::string* str);
+
+std::string HumanReadableNumber(double n, double one_k = 1024.0);
+
+#ifdef __GNUC__
+__attribute__((format(printf, 1, 2)))
+#endif
+std::string
+StrFormat(const char* format, ...);
+
+inline std::ostream& StrCatImp(std::ostream& out) BENCHMARK_NOEXCEPT {
+  return out;
+}
+
+template <class First, class... Rest>
+inline std::ostream& StrCatImp(std::ostream& out, First&& f, Rest&&... rest) {
+  out << std::forward<First>(f);
+  return StrCatImp(out, std::forward<Rest>(rest)...);
+}
+
+template <class... Args>
+inline std::string StrCat(Args&&... args) {
+  std::ostringstream ss;
+  StrCatImp(ss, std::forward<Args>(args)...);
+  return ss.str();
+}
+
+void ReplaceAll(std::string* str, const std::string& from,
+                const std::string& to);
+
+#ifdef BENCHMARK_STL_ANDROID_GNUSTL
+/*
+ * GNU STL in Android NDK lacks support for some C++11 functions, including
+ * stoul, stoi, stod. We reimplement them here using C functions strtoul,
+ * strtol, strtod. Note that reimplemented functions are in benchmark::
+ * namespace, not std:: namespace.
+ */
+unsigned long stoul(const std::string& str, size_t* pos = nullptr,
+                           int base = 10);
+int stoi(const std::string& str, size_t* pos = nullptr, int base = 10);
+double stod(const std::string& str, size_t* pos = nullptr);
+#else
+using std::stoul;
+using std::stoi;
+using std::stod;
+#endif
+
+}  // end namespace benchmark
+
+#endif  // BENCHMARK_STRING_UTIL_H_