diff --git a/src/fellchensammlung/tools/geo.py b/src/fellchensammlung/tools/geo.py
index cad9ac3..5acce58 100644
--- a/src/fellchensammlung/tools/geo.py
+++ b/src/fellchensammlung/tools/geo.py
@@ -2,9 +2,35 @@ import requests
 import json
 from notfellchen import __version__ as nf_version
 
+from math import radians, sqrt, sin, cos, atan2
+
+
+def calculate_distance_between_coordinates(position1, position2):
+    """
+    Calculate the distance between two points identified by coordinates
+    It expects the coordinates to be a tuple (lat, lon)
+
+    Based on https://en.wikipedia.org/wiki/Haversine_formula
+    """
+    earth_radius_km = 6371
+    latitude1 = float(position1[0])
+    longitude1 = float(position1[1])
+    latitude2 = float(position2[0])
+    longitude2 = float(position2[1])
+
+    distance_lat = radians(latitude2 - latitude1)
+    distance_long = radians(longitude2 - longitude1)
+
+    a = pow(sin(distance_lat / 2), 2) + cos(radians(latitude1)) * cos(radians(latitude2)) * pow(sin(distance_long / 2), 2)
+    c = 2 * atan2(sqrt(a), sqrt(1 - a))
+
+    distance_in_km = earth_radius_km * c
+
+    return distance_in_km
 
 class ResponseMock:
     content = b'[{"place_id":138181499,"licence":"Data \xc2\xa9 OpenStreetMap contributors, ODbL 1.0. http://osm.org/copyright","osm_type":"relation","osm_id":1247237,"lat":"48.4949904","lon":"9.040330235970146","category":"boundary","type":"postal_code","place_rank":21, "importance":0.12006895017929346,"addresstype":"postcode","name":"72072","display_name":"72072, Derendingen, T\xc3\xbcbingen, Landkreis T\xc3\xbcbingen, Baden-W\xc3\xbcrttemberg, Deutschland", "boundingbox":["48.4949404","48.4950404","9.0402802","9.0403802"]}]'
+    status_code = 200
 
     def json(self):
         return json.loads(self.content.decode())
@@ -36,3 +62,4 @@ class GeoAPI:
 if __name__ == "__main__":
     geo = GeoAPI(debug=True)
     print(geo.get_coordinates_from_postcode("72072"))
+    print(calculate_distance_between_coordinates(('48.4949904', '9.040330235970146'), ("48.648333", "9.451111")))