Hello, the current implementation function for hashing of floating point types, the function template float_hash_value<> in hash.hpp, is implicitely written for real types where std::numeric_limits<T>::radix == 2. Although base = 2 is probably the most prominent case, it is not the only representation compatible with Our Holy Standard. E.g. base 16 floating types are well-known to exist. The hidden assumption becomes obvious in the formular std::size_t const length = (std::numeric_limits<T>::digits + std::numeric_limits<int>::digits - 1) / std::numeric_limits<int>::digits; which should actually mean (pseudo formular): std::size_t const length = (std::numeric_limits<T>::digits2 + std::numeric_limits<int>::digits - 1) / std::numeric_limits<int>::digits; where the (non-existing) constant digits2 would describe the "Number of base 2 digits that can be represented without change." To my opinion boost itself provides a simple helper class, namely static_log2, which allows the correct implementation by using the extended formular #include <boost/integer/static_log2.hpp> ... std::size_t const length = (std::numeric_limits<T>::digits * boost::static_log2<std::numeric_limits<T >::radix>::value + std::numeric_limits<int>::digits - 1) / std::numeric_limits<int>::digits; Note that the expression boost::static_log2<std::numeric_limits<T>::radix>::value is exactly 1 in the usual base-2 case, but e.g. 4 in case of base-16. My proposed fix is exact in all cases, where radix is a power of 2, in other cases (like base-10) it would at least be a better approximation than the current one. Greetings from Bremen, Daniel Krügler