diff --git a/firmware/config.h b/firmware/config.h
index efb0d5d..66d6d40 100644
--- a/firmware/config.h
+++ b/firmware/config.h
@@ -27,10 +27,14 @@
 #define WIFI_MINIMUM_SIGNAL_QUALITY      10 // percent
 #define RESET_ESP_TIME_INTERVAL_MS  3600000
 
-#define ROTOR_LENGTH_KM             0.0000825
-#define WIND_SENSOR_MEAS_TIME_S           5.0
-#define SEC_TO_HOUR_FACTOR      (60.0 * 60.0)
-#define COUNT_TO_KMH            ((TWO_PI * ROTOR_LENGTH_KM /  WIND_SENSOR_MEAS_TIME_S) * SEC_TO_HOUR_FACTOR)
+#define WIND_SENSOR_MEAS_TIME_S                      5.0
+#define ROTOR_LENGTH_CM                             8.25
+#define ROTOR_LENGTH_M          (ROTOR_LENGTH_CM / 100.0)
+#define ROTOR_LENGTH_KM         (ROTOR_LENGTH_M / 1000.0)
+#define SEC_TO_HOUR_FACTOR                  (60.0 * 60.0)
+#define COUNT_TO_KMH            ((TWO_PI * ROTOR_LENGTH_KM / WIND_SENSOR_MEAS_TIME_S) * SEC_TO_HOUR_FACTOR)
+#define COUNT_TO_MPS             (TWO_PI * ROTOR_LENGTH_M  / WIND_SENSOR_MEAS_TIME_S)
+#define WINDSPEED_FACTOR                     COUNT_TO_MPS
 
 #define BAT_LOW_VOLTAGE                 3.6
 #define BAT_EMERGENCY_DEEPSLEEP_VOLTAGE 3.5
diff --git a/firmware/sensor_wind.ino b/firmware/sensor_wind.ino
index cfda894..f7cd6bd 100644
--- a/firmware/sensor_wind.ino
+++ b/firmware/sensor_wind.ino
@@ -23,7 +23,7 @@ float wind_speed()
   detachInterrupt(interruptNumber);
 
   // calculate the speed as km/h
-  float tmp_speed = (float)anemometerRotations * COUNT_TO_KMH;
+  float tmp_speed = (float)anemometerRotations * WINDSPEED_FACTOR;
 
 #ifdef DEBUG
   Serial.print("Windspeed: " + String(tmp_speed));