diff --git a/sprout/cstdlib/conversion.hpp b/sprout/cstdlib/conversion.hpp
index f1c3bc5d..e133d6f4 100644
--- a/sprout/cstdlib/conversion.hpp
+++ b/sprout/cstdlib/conversion.hpp
@@ -16,5 +16,7 @@
 #include <sprout/cstdlib/strtof.hpp>
 #include <sprout/cstdlib/strtod.hpp>
 #include <sprout/cstdlib/strtold.hpp>
+#include <sprout/cstdlib/strtoimax.hpp>
+#include <sprout/cstdlib/strtoumax.hpp>
 
 #endif	// #ifndef SPROUT_CSTDLIB_CONVERSION_HPP
diff --git a/sprout/cstdlib/strtoimax.hpp b/sprout/cstdlib/strtoimax.hpp
new file mode 100644
index 00000000..0c0562cc
--- /dev/null
+++ b/sprout/cstdlib/strtoimax.hpp
@@ -0,0 +1,30 @@
+#ifndef SPROUT_CSTDLIB_STRTOIMAX_HPP
+#define SPROUT_CSTDLIB_STRTOIMAX_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <sprout/config.hpp>
+#include <sprout/cstdlib/str_to_int.hpp>
+
+namespace sprout {
+	//
+	// strtol
+	//
+	inline SPROUT_CONSTEXPR std::intmax_t strtoimax(char const* str, char** endptr, int base = 10){
+		return sprout::str_to_int<std::intmax_t>(str, endptr, base);
+	}
+	template<typename Char>
+	inline SPROUT_CONSTEXPR std::intmax_t strtoimax(Char const* str, Char** endptr, int base = 10){
+		return sprout::str_to_int<std::intmax_t>(str, endptr, base);
+	}
+	template<typename Char>
+	inline SPROUT_CONSTEXPR std::intmax_t strtoimax(Char const* str, std::nullptr_t endptr, int base = 10){
+		return sprout::str_to_int<std::intmax_t>(str, base);
+	}
+	template<typename Char>
+	inline SPROUT_CONSTEXPR std::intmax_t strtoimax(Char const* str, int base = 10){
+		return sprout::str_to_int<std::intmax_t>(str, base);
+	}
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_CSTDLIB_STRTOIMAX_HPP
diff --git a/sprout/cstdlib/strtoumax.hpp b/sprout/cstdlib/strtoumax.hpp
new file mode 100644
index 00000000..e200629b
--- /dev/null
+++ b/sprout/cstdlib/strtoumax.hpp
@@ -0,0 +1,30 @@
+#ifndef SPROUT_CSTDLIB_STRTTOUMAX_HPP
+#define SPROUT_CSTDLIB_STRTTOUMAX_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <sprout/config.hpp>
+#include <sprout/cstdlib/str_to_int.hpp>
+
+namespace sprout {
+	//
+	// strtoul
+	//
+	inline SPROUT_CONSTEXPR std::uintmax_t strtoumax(char const* str, char** endptr, int base = 10){
+		return sprout::str_to_int<std::uintmax_t>(str, endptr, base);
+	}
+	template<typename Char>
+	inline SPROUT_CONSTEXPR std::uintmax_t strtoumax(Char const* str, Char** endptr, int base = 10){
+		return sprout::str_to_int<std::uintmax_t>(str, endptr, base);
+	}
+	template<typename Char>
+	inline SPROUT_CONSTEXPR std::uintmax_t strtoumax(Char const* str, std::nullptr_t endptr, int base = 10){
+		return sprout::str_to_int<std::uintmax_t>(str, base);
+	}
+	template<typename Char>
+	inline SPROUT_CONSTEXPR std::uintmax_t strtoumax(Char const* str, int base = 10){
+		return sprout::str_to_int<std::uintmax_t>(str, base);
+	}
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_CSTDLIB_STRTTOUMAX_HPP
diff --git a/sprout/string/string_to_int.hpp b/sprout/string/string_to_int.hpp
index 05463a65..9d5c58d3 100644
--- a/sprout/string/string_to_int.hpp
+++ b/sprout/string/string_to_int.hpp
@@ -2,6 +2,7 @@
 #define SPROUT_STRING_STRING_TO_INT_HPP
 
 #include <cstddef>
+#include <cstdint>
 #include <string>
 #include <type_traits>
 #include <sprout/config.hpp>
@@ -111,6 +112,30 @@ namespace sprout {
 		return sprout::string_to_int<unsigned long long>(str, base);
 	}
 
+	//
+	// stoimax
+	//
+	template<typename Elem, std::size_t N, typename Traits>
+	inline SPROUT_CONSTEXPR std::intmax_t stoimax(sprout::basic_string<Elem, N, Traits> const& str, std::size_t* idx, int base = 10) {
+		return sprout::string_to_int<std::intmax_t>(str, idx, base);
+	}
+	template<typename Elem, std::size_t N, typename Traits>
+	inline SPROUT_CONSTEXPR std::intmax_t stoimax(sprout::basic_string<Elem, N, Traits> const& str, int base = 10) {
+		return sprout::string_to_int<std::intmax_t>(str, base);
+	}
+
+	//
+	// stoumax
+	//
+	template<typename Elem, std::size_t N, typename Traits>
+	inline SPROUT_CONSTEXPR std::uintmax_t stoumax(sprout::basic_string<Elem, N, Traits> const& str, std::size_t* idx, int base = 10) {
+		return sprout::string_to_int<std::uintmax_t>(str, idx, base);
+	}
+	template<typename Elem, std::size_t N, typename Traits>
+	inline SPROUT_CONSTEXPR std::uintmax_t stoumax(sprout::basic_string<Elem, N, Traits> const& str, int base = 10) {
+		return sprout::string_to_int<std::uintmax_t>(str, base);
+	}
+
 	//
 	// from_string
 	//