diff --git a/README.md b/README.md
index ade8f65..cd7096b 100644
--- a/README.md
+++ b/README.md
@@ -20,3 +20,7 @@ Implemented are the follwing [Window functions](https://en.wikipedia.org/wiki/Wi
 * [Gaussian window](https://en.wikipedia.org/wiki/Window_function#Gaussian_window)
 * [Kaiser window](https://en.wikipedia.org/wiki/Window_function#Kaiser_window)
 
+### [const.hh](const.hh)
+
+Some constants we need
+
diff --git a/const.hh b/const.hh
new file mode 100644
index 0000000..7590e18
--- /dev/null
+++ b/const.hh
@@ -0,0 +1,21 @@
+/*
+Some constants
+
+Copyright 2018 Ahmet Inan <inan@aicodix.de>
+*/
+
+#ifndef CONST_HH
+#define CONST_HH
+
+namespace DSP {
+
+template <typename T>
+struct Const {
+	static inline T Pi()	{ return 3.14159265358979323846; } // 4*a(1)
+	static inline T TwoPi()	{ return 6.28318530717958647693; } // 8*a(1)
+};
+
+}
+
+#endif
+