diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index ddcdf989..448c5219 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -46,6 +46,7 @@ add_mp_units_module(
             include/mp-units/ext/algorithm.h
             include/mp-units/ext/contracts.h
             include/mp-units/ext/fixed_string.h
+            include/mp-units/ext/inplace_vector.h
             include/mp-units/ext/prime.h
             include/mp-units/ext/type_name.h
             include/mp-units/ext/type_traits.h
diff --git a/src/core/include/mp-units/ext/inplace_vector.h b/src/core/include/mp-units/ext/inplace_vector.h
new file mode 100644
index 00000000..58970e5f
--- /dev/null
+++ b/src/core/include/mp-units/ext/inplace_vector.h
@@ -0,0 +1,137 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+// Very simplified implementation of std::inplace_vector
+// To be replaced with:
+// P0843: std::inplace_vector
+
+#include <mp-units/bits/hacks.h>  // IWYU pragma: keep
+
+#ifndef MP_UNITS_IN_MODULE_INTERFACE
+#include <mp-units/ext/contracts.h>
+#include <concepts>
+#include <cstddef>
+#include <ranges>
+#endif
+
+// NOLINTBEGIN(*-avoid-c-arrays)
+#pragma once
+
+namespace mp_units::detail {
+template<class T, std::size_t N>
+class inplace_vector {
+public:
+  using value_type = T;
+  using pointer = T*;
+  using const_pointer = const T*;
+  using reference = value_type&;
+  using const_reference = const value_type&;
+  using size_type = std::size_t;
+  using difference_type = std::ptrdiff_t;
+  using iterator = pointer;
+  using const_iterator = const_pointer;
+  using reverse_iterator = std::reverse_iterator<iterator>;
+  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+
+  constexpr inplace_vector() noexcept = default;
+
+  // iterators
+  constexpr iterator begin() noexcept { return data(); }
+  constexpr const_iterator begin() const noexcept { return data(); }
+  constexpr iterator end() noexcept { return begin() + size(); }
+  constexpr const_iterator end() const noexcept { return begin() + size(); }
+  constexpr reverse_iterator rbegin() noexcept { return reverse_iterator(end()); }
+  constexpr const_reverse_iterator rbegin() const noexcept { return const_reverse_iterator(end()); }
+  constexpr reverse_iterator rend() noexcept { return reverse_iterator(begin()); }
+  constexpr const_reverse_iterator rend() const noexcept { return const_reverse_iterator(begin()); }
+
+  constexpr const_iterator cbegin() const noexcept { return data(); }
+  constexpr const_iterator cend() const noexcept { return cbegin() + size(); }
+  constexpr const_reverse_iterator crbegin() const noexcept { return const_reverse_iterator(cend()); }
+  constexpr const_reverse_iterator crend() const noexcept { return const_reverse_iterator(cbegin()); }
+
+  [[nodiscard]] constexpr bool empty() const noexcept { return size() == 0; };
+  [[nodiscard]] constexpr size_type size() const noexcept { return size_; }
+  [[nodiscard]] static constexpr size_type max_size() noexcept { return N; }
+  [[nodiscard]] static constexpr size_type capacity() noexcept { return N; }
+
+  // element access
+  constexpr reference operator[](size_type n) { return data_[n]; }
+  constexpr const_reference operator[](size_type n) const { return data_[n]; }
+  constexpr reference front() { return *data(); }
+  constexpr const_reference front() const { return *data(); }
+  constexpr reference back() { return *(data() + size() - 1); }
+  constexpr const_reference back() const { return *(data() + size() - 1); }
+
+  // data access
+  constexpr T* data() noexcept { return data_; }
+  constexpr const T* data() const noexcept { return data_; }
+
+  constexpr reference push_back(const T& v)
+    requires std::constructible_from<T, const T&>
+  {
+    return emplace_back(v);
+  }
+
+  constexpr reference push_back(T&& v)
+    requires std::constructible_from<T, T&&>
+  {
+    return emplace_back(std::forward<T&&>(v));
+  }
+
+  template<typename... Args>
+    requires(std::constructible_from<T, Args...>)
+  constexpr T& unchecked_emplace_back(Args&&... args)
+  {
+    std::construct_at(end(), std::forward<Args>(args)...);
+    ++size_;
+    return back();
+  }
+
+  template<typename... Args>
+    requires(std::constructible_from<T, Args...>)
+  constexpr T* try_emplace_back(Args&&... args)
+  {
+    if (size() == capacity()) return nullptr;
+    return &unchecked_emplace_back(std::forward<Args>(args)...);
+  }
+
+  template<typename... Args>
+    requires std::constructible_from<T, Args...>
+  constexpr reference emplace_back(Args&&... args)
+  {
+    MP_UNITS_EXPECTS(size() < capacity());
+    auto ptr = try_emplace_back(std::forward<Args>(args)...);
+#if MP_UNITS_HOSTED
+    if (!ptr) throw std::runtime_error("not enough capacity");
+#endif
+    return *ptr;
+  }
+
+private:
+  T data_[N];
+  size_type size_ = 0;
+};
+
+}  // namespace mp_units::detail
+
+// NOLINTEND(*-avoid-c-arrays)