diff --git a/CMakeLists.txt b/CMakeLists.txt
index 42189a03..07400758 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -77,6 +77,7 @@ endfunction()
 
 compiled_test(test/adaptive_storage_test.cpp)
 compiled_test(test/algorithm_project_test.cpp)
+compiled_test(test/algorithm_sum_test.cpp)
 compiled_test(test/axis_regular_test.cpp)
 compiled_test(test/axis_circular_test.cpp)
 compiled_test(test/axis_variable_test.cpp)
diff --git a/include/boost/histogram/algorithm/sum.hpp b/include/boost/histogram/algorithm/sum.hpp
new file mode 100644
index 00000000..ecdd1ce5
--- /dev/null
+++ b/include/boost/histogram/algorithm/sum.hpp
@@ -0,0 +1,27 @@
+// Copyright 2018 Hans Dembinski
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt
+// or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_HISTOGRAM_ALGORITHM_SUM_HPP
+#define BOOST_HISTOGRAM_ALGORITHM_SUM_HPP
+
+#include <boost/histogram/histogram_fwd.hpp>
+#include <numeric>
+#include <type_traits>
+
+namespace boost {
+namespace histogram {
+namespace algorithm {
+template <typename A, typename S>
+typename histogram<A, S>::value_type sum(const histogram<A, S>& h) {
+  using T = typename histogram<A, S>::value_type;
+  return std::accumulate(h.begin(), h.end(),
+                         std::conditional_t<std::is_integral<T>::value, double, T>());
+}
+} // namespace algorithm
+} // namespace histogram
+} // namespace boost
+
+#endif
diff --git a/include/boost/histogram/detail/meta.hpp b/include/boost/histogram/detail/meta.hpp
index 125fb3f2..ce30566d 100644
--- a/include/boost/histogram/detail/meta.hpp
+++ b/include/boost/histogram/detail/meta.hpp
@@ -227,28 +227,25 @@ using is_sample = is_sample_impl<unqual<T>>;
 template <typename T, typename = decltype(*std::declval<T&>(), ++std::declval<T&>())>
 struct requires_iterator {};
 
-template <typename T, typename = mp11::mp_if<is_iterable<T>, void>>
+template <typename T, typename = mp11::mp_if<is_iterable<unqual<T>>, void>>
 struct requires_iterable {};
 
-template <typename T, typename = mp11::mp_if<is_tuple<T>, void>>
+template <typename T, typename = mp11::mp_if<is_tuple<unqual<T>>, void>>
 struct requires_tuple {};
 
-template <typename T, typename = mp11::mp_if<is_axis<T>, void>>
+template <typename T, typename = mp11::mp_if<is_axis<unqual<T>>, void>>
 struct requires_axis {};
 
-template <typename T, typename = mp11::mp_if<is_axis_or_axis_variant<T>, void>>
+template <typename T, typename = mp11::mp_if<is_axis_or_axis_variant<unqual<T>>, void>>
 struct requires_axis_or_axis_variant {};
 
-template <typename T, typename = mp11::mp_if<is_axis_vector<T>, void>>
+template <typename T, typename = mp11::mp_if<is_axis_vector<unqual<T>>, void>>
 struct requires_axis_vector {};
 
-template <typename T, typename U, typename = mp11::mp_if<std::is_same<T, U>, void>>
-struct requires_same {};
-
-template <typename T, typename = mp11::mp_if<is_transform<T>, void>>
+template <typename T, typename = mp11::mp_if<is_transform<unqual<T>>, void>>
 struct requires_transform {};
 
-template <typename T, typename = mp11::mp_if<is_storage<T>, void>>
+template <typename T, typename = mp11::mp_if<is_storage<unqual<T>>, void>>
 struct requires_storage {};
 
 } // namespace detail
diff --git a/test/algorithm_project_test.cpp b/test/algorithm_project_test.cpp
index 2547ffa2..07422702 100644
--- a/test/algorithm_project_test.cpp
+++ b/test/algorithm_project_test.cpp
@@ -6,6 +6,7 @@
 
 #include <boost/core/lightweight_test.hpp>
 #include <boost/histogram/algorithm/project.hpp>
+#include <boost/histogram/algorithm/sum.hpp>
 #include <boost/histogram/axis/integer.hpp>
 #include <boost/histogram/axis/ostream_operators.hpp>
 #include <boost/histogram/literals.hpp>
@@ -14,7 +15,7 @@
 
 using namespace boost::histogram;
 using namespace boost::histogram::literals; // to get _c suffix
-using boost::histogram::algorithm::project;
+using namespace boost::histogram::algorithm;
 
 template <typename Tag>
 void run_tests() {
diff --git a/test/algorithm_sum_test.cpp b/test/algorithm_sum_test.cpp
new file mode 100644
index 00000000..2e8f2438
--- /dev/null
+++ b/test/algorithm_sum_test.cpp
@@ -0,0 +1,46 @@
+// Copyright 2018 Hans Dembinski
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt
+// or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/core/lightweight_test.hpp>
+#include <boost/histogram.hpp>
+#include <boost/histogram/algorithm/sum.hpp>
+#include "utility_histogram.hpp"
+
+using namespace boost::histogram;
+using namespace boost::histogram::literals; // to get _c suffix
+using boost::histogram::algorithm::sum;
+
+template <typename Tag>
+void run_tests() {
+  auto ax = axis::integer<>(0, 100);
+
+  auto h1 = make(Tag(), ax);
+  for (unsigned i = 0; i < 100; ++i) h1(i);
+  BOOST_TEST_EQ(sum(h1), 100);
+
+  auto h2 = make_s(Tag(), std::vector<double>(), ax, ax);
+  for (unsigned i = 0; i < 100; ++i)
+    for (unsigned j = 0; j < 100; ++j) h2(i, j);
+
+  BOOST_TEST_EQ(sum(h2), 100000);
+
+  auto h3 = make_s(Tag(), std::array<int, 102>(), ax);
+  for (unsigned i = 0; i < 100; ++i) h3(i);
+
+  BOOST_TEST_EQ(sum(h3), 100);
+
+  auto h4 = make_s(Tag(), std::unordered_map<std::size_t, int>(), ax);
+  for (unsigned i = 0; i < 100; ++i) h3(i);
+
+  BOOST_TEST_EQ(sum(h3), 100);
+}
+
+int main() {
+  run_tests<static_tag>();
+  run_tests<dynamic_tag>();
+
+  return boost::report_errors();
+}
diff --git a/test/histogram_test.cpp b/test/histogram_test.cpp
index 84fe615c..61ddd0a3 100644
--- a/test/histogram_test.cpp
+++ b/test/histogram_test.cpp
@@ -9,6 +9,7 @@
 #include <boost/histogram/accumulators/ostream_operators.hpp>
 #include <boost/histogram/accumulators/weight.hpp>
 #include <boost/histogram/adaptive_storage.hpp>
+#include <boost/histogram/algorithm/sum.hpp>
 #include <boost/histogram/axis/variant.hpp>
 #include <boost/histogram/histogram.hpp>
 #include <boost/histogram/literals.hpp>
@@ -133,12 +134,12 @@ void run_tests() {
     h(0, 0);
     const auto href = h;
     decltype(h) h2(std::move(h));
-    BOOST_TEST_EQ(sum(h), 0);
+    BOOST_TEST_EQ(algorithm::sum(h), 0);
     BOOST_TEST_EQ(h.size(), 0);
     BOOST_TEST_EQ(h2, href);
     decltype(h) h3;
     h3 = std::move(h2);
-    BOOST_TEST_EQ(sum(h2), 0);
+    BOOST_TEST_EQ(algorithm::sum(h2), 0);
     BOOST_TEST_EQ(h2.size(), 0);
     BOOST_TEST_EQ(h3, href);
   }
@@ -224,7 +225,7 @@ void run_tests() {
 
     BOOST_TEST_EQ(h.rank(), 1);
     BOOST_TEST_EQ(h.axis().size(), 2);
-    BOOST_TEST_EQ(sum(h), 4);
+    BOOST_TEST_EQ(algorithm::sum(h), 4);
 
     BOOST_TEST_EQ(h.at(-1), 1);
     BOOST_TEST_EQ(h.at(0), 2);
@@ -242,7 +243,7 @@ void run_tests() {
 
     BOOST_TEST_EQ(h.rank(), 1);
     BOOST_TEST_EQ(h.axis().size(), 2);
-    BOOST_TEST_EQ(sum(h), 2);
+    BOOST_TEST_EQ(algorithm::sum(h), 2);
 
     BOOST_TEST_EQ(h.at(0), 2);
     BOOST_TEST_EQ(h.at(1), 0);
@@ -258,7 +259,7 @@ void run_tests() {
 
     BOOST_TEST_EQ(h.rank(), 1);
     BOOST_TEST_EQ(h.axis().size(), 2);
-    BOOST_TEST_EQ(sum(h), 4);
+    BOOST_TEST_EQ(algorithm::sum(h), 4);
 
     BOOST_TEST_EQ(h.at(0), 1);
     BOOST_TEST_EQ(h.at(1), 1);
@@ -274,8 +275,8 @@ void run_tests() {
     h(1);
     h(weight(2), 2);
 
-    BOOST_TEST_EQ(sum(h).value(), 5.5);
-    BOOST_TEST_EQ(sum(h).variance(), 7.25);
+    BOOST_TEST_EQ(algorithm::sum(h).value(), 5.5);
+    BOOST_TEST_EQ(algorithm::sum(h).variance(), 7.25);
 
     BOOST_TEST_EQ(h[-1].value(), 1);
     BOOST_TEST_EQ(h[-1].variance(), 1);
@@ -321,7 +322,7 @@ void run_tests() {
     BOOST_TEST_EQ(h.rank(), 2);
     BOOST_TEST_EQ(h.axis(0_c).size(), 2);
     BOOST_TEST_EQ(h.axis(1_c).size(), 3);
-    BOOST_TEST_EQ(sum(h), 3);
+    BOOST_TEST_EQ(algorithm::sum(h), 3);
 
     BOOST_TEST_EQ(h.at(-1, 0), 0);
     BOOST_TEST_EQ(h.at(-1, 1), 1);
@@ -350,8 +351,8 @@ void run_tests() {
     h(weight(5), -1, -10); // is ignored
     h(weight(7), -10, 0);  // -> -1, 1
 
-    BOOST_TEST_EQ(sum(h).value(), 18);
-    BOOST_TEST_EQ(sum(h).variance(), 150);
+    BOOST_TEST_EQ(algorithm::sum(h).value(), 18);
+    BOOST_TEST_EQ(algorithm::sum(h).variance(), 150);
 
     BOOST_TEST_EQ(h.at(-1, 0).value(), 0);
     BOOST_TEST_EQ(h.at(-1, 1).value(), 7);
@@ -498,7 +499,7 @@ void run_tests() {
     BOOST_TEST_EQ(h.at(0), 1);
     BOOST_TEST_EQ(h.at(1), 1);
     BOOST_TEST_EQ(h.at(2), 1);
-    BOOST_TEST_EQ(sum(h), 3);
+    BOOST_TEST_EQ(algorithm::sum(h), 3);
 
     auto a = std::vector<double>();
     std::partial_sum(h.begin(), h.end(), std::back_inserter(a));
@@ -562,11 +563,11 @@ void run_tests() {
     h(1);
     BOOST_TEST_EQ(h.at(0), 1);
     BOOST_TEST_EQ(h.at(1), 1);
-    BOOST_TEST_EQ(sum(h), 2);
+    BOOST_TEST_EQ(algorithm::sum(h), 2);
     h.reset();
     BOOST_TEST_EQ(h.at(0), 0);
     BOOST_TEST_EQ(h.at(1), 0);
-    BOOST_TEST_EQ(sum(h), 0);
+    BOOST_TEST_EQ(algorithm::sum(h), 0);
   }
 
   // custom axes
@@ -696,7 +697,7 @@ void run_tests() {
     ++it;
     BOOST_TEST(it == h.end());
 
-    auto v = sum(h);
+    auto v = algorithm::sum(h);
     BOOST_TEST_EQ(v.value(), 4);
     BOOST_TEST_EQ(v.variance(), 6);
   }
diff --git a/test/utility_histogram.hpp b/test/utility_histogram.hpp
index 78970eb6..965062cf 100644
--- a/test/utility_histogram.hpp
+++ b/test/utility_histogram.hpp
@@ -17,10 +17,6 @@
 
 namespace boost {
 namespace histogram {
-template <typename Histogram>
-auto sum(const Histogram& h) {
-  return std::accumulate(h.begin(), h.end(), typename Histogram::value_type(0));
-}
 
 template <typename... Ts>
 auto make_axis_vector(Ts&&... ts) {