diff --git a/README.md b/README.md
index d8feffb..95c9e72 100644
--- a/README.md
+++ b/README.md
@@ -89,6 +89,13 @@ Implemented are the following [trigger functions](https://en.wikipedia.org/wiki/
 
 The [simple moving average](https://en.wikipedia.org/wiki/Moving_average#Simple_moving_average) gives us the mean of the last N data points.
 
+### [calculus.hh](calculus.hh)
+
+Some [calculus](https://en.wikipedia.org/wiki/Calculus) functions:
+
+* [Integrator](https://en.wikipedia.org/wiki/Integrator)
+* [Differentiator](https://en.wikipedia.org/wiki/Differentiator)
+
 ### [const.hh](const.hh)
 
 Some constants we need
diff --git a/calculus.hh b/calculus.hh
new file mode 100644
index 0000000..6aced55
--- /dev/null
+++ b/calculus.hh
@@ -0,0 +1,42 @@
+/*
+Some calculus functions
+
+Copyright 2019 Ahmet Inan <inan@aicodix.de>
+*/
+
+#pragma once
+
+namespace DSP {
+
+template <typename TYPE>
+class Integrator
+{
+	TYPE sum;
+public:
+	constexpr Integrator(TYPE sum = TYPE(0)) : sum(sum)
+	{
+	}
+	TYPE operator()(TYPE input)
+	{
+		return sum += input;
+	}
+};
+
+template <typename TYPE>
+class Differentiator
+{
+	TYPE prev;
+public:
+	constexpr Differentiator(TYPE prev = TYPE(0)) : prev(prev)
+	{
+	}
+	TYPE operator()(TYPE input)
+	{
+		TYPE diff = input - prev;
+		prev = input;
+		return diff;
+	}
+};
+
+}
+