diff --git a/libraries/AP_Baro/AP_Baro.cpp b/libraries/AP_Baro/AP_Baro.cpp
index 5d726a5bc9..e2572bab1e 100644
--- a/libraries/AP_Baro/AP_Baro.cpp
+++ b/libraries/AP_Baro/AP_Baro.cpp
@@ -403,7 +403,8 @@ float AP_Baro::get_sealevel_pressure(float pressure) const
 {
     float temp    = C_TO_KELVIN(get_ground_temperature());
     float p0_sealevel;
-
+    // This is an exact calculation that is within +-2.5m of the standard
+    // atmosphere tables in the troposphere (up to 11,000 m amsl).
     p0_sealevel = 8.651154799255761e30f*pressure*powF((769231.0f-(5000.0f*_field_elevation_active)/temp),-5.255993146184937f);
 
     return p0_sealevel;