diff --git a/firmware/config.h b/firmware/config.h
index 5fc9260..efb0d5d 100644
--- a/firmware/config.h
+++ b/firmware/config.h
@@ -27,7 +27,7 @@
 #define WIFI_MINIMUM_SIGNAL_QUALITY      10 // percent
 #define RESET_ESP_TIME_INTERVAL_MS  3600000
 
-#define ROTOR_LENGTH_KM              0.000016 // 1.6cm
+#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)