diff --git a/libraries/AP_Motors/AP_MotorsMulticopter.cpp b/libraries/AP_Motors/AP_MotorsMulticopter.cpp
index d0b59e0bae..98dd44dcc4 100644
--- a/libraries/AP_Motors/AP_MotorsMulticopter.cpp
+++ b/libraries/AP_Motors/AP_MotorsMulticopter.cpp
@@ -556,6 +556,7 @@ void AP_MotorsMulticopter::output_logic()
         _spool_up_time.set(0.05);
     }
 
+    const float spool_step = 1.0f / (_spool_up_time * _loop_rate);
     switch (_spool_state) {
     case SpoolState::SHUT_DOWN:
         // Motors should be stationary.
@@ -595,7 +596,6 @@ void AP_MotorsMulticopter::output_logic()
         limit.throttle_upper = true;
 
         // set and increment ramp variables
-        float spool_step = 1.0f / (_spool_up_time * _loop_rate);
         switch (_spool_desired) {
         case DesiredSpoolState::SHUT_DOWN:
             _spin_up_ratio -= spool_step;
@@ -649,7 +649,7 @@ void AP_MotorsMulticopter::output_logic()
 
         // set and increment ramp variables
         _spin_up_ratio = 1.0f;
-        _throttle_thrust_max += 1.0f / (_spool_up_time * _loop_rate);
+        _throttle_thrust_max += spool_step;
 
         // constrain ramp value and update mode
         if (_throttle_thrust_max >= MIN(get_throttle(), get_current_limit_max_throttle())) {
@@ -661,7 +661,7 @@ void AP_MotorsMulticopter::output_logic()
 
         // initialise motor failure variables
         _thrust_boost = false;
-        _thrust_boost_ratio = MAX(0.0, _thrust_boost_ratio - 1.0 / (_spool_up_time * _loop_rate));
+        _thrust_boost_ratio = MAX(0.0, _thrust_boost_ratio - spool_step);
         break;
 
     case SpoolState::THROTTLE_UNLIMITED:
@@ -686,9 +686,9 @@ void AP_MotorsMulticopter::output_logic()
         _throttle_thrust_max = get_current_limit_max_throttle();
 
         if (_thrust_boost && !_thrust_balanced) {
-            _thrust_boost_ratio = MIN(1.0, _thrust_boost_ratio + 1.0f / (_spool_up_time * _loop_rate));
+            _thrust_boost_ratio = MIN(1.0, _thrust_boost_ratio + spool_step);
         } else {
-            _thrust_boost_ratio = MAX(0.0, _thrust_boost_ratio - 1.0f / (_spool_up_time * _loop_rate));
+            _thrust_boost_ratio = MAX(0.0, _thrust_boost_ratio - spool_step);
         }
         break;
 
@@ -711,7 +711,7 @@ void AP_MotorsMulticopter::output_logic()
 
         // set and increment ramp variables
         _spin_up_ratio = 1.0f;
-        _throttle_thrust_max -= 1.0f / (_spool_up_time * _loop_rate);
+        _throttle_thrust_max -= spool_step;
 
         // constrain ramp value and update mode
         if (_throttle_thrust_max <= 0.0f) {
@@ -723,7 +723,7 @@ void AP_MotorsMulticopter::output_logic()
             _spool_state = SpoolState::GROUND_IDLE;
         }
 
-        _thrust_boost_ratio = MAX(0.0, _thrust_boost_ratio - 1.0f / (_spool_up_time * _loop_rate));
+        _thrust_boost_ratio = MAX(0.0, _thrust_boost_ratio - spool_step);
         break;
     }
 }