diff --git a/calculate.hpp b/calculate.hpp
new file mode 100644
index 0000000..fdf200f
--- /dev/null
+++ b/calculate.hpp
@@ -0,0 +1,15 @@
+#pragma once
+
+#include <functional>
+#include <map>
+#include <string>
+#include <vector>
+
+namespace phosphor::virtual_sensor
+{
+
+using Interface = std::string;
+using CalculationFunc = std::function<double(std::vector<double>&)>;
+extern std::map<Interface, CalculationFunc> calculationIfaces;
+
+} // namespace phosphor::virtual_sensor