diff --git a/defaults.h b/defaults.h
index c17e95a..dd46144 100644
--- a/defaults.h
+++ b/defaults.h
@@ -36,7 +36,7 @@
   #define DEFAULT_MM_PER_ARC_SEGMENT 0.1
   #define DEFAULT_RAPID_FEEDRATE 500.0 // mm/min
   #define DEFAULT_FEEDRATE 250.0
-  #define DEFAULT_ACCELERATION (10.0*60*60) // 10 mm/min^2
+  #define DEFAULT_ACCELERATION (10.0*60*60) // 10*60*60 mm/min^2 = 10 mm/s^2
   #define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
   #define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT))
   #define DEFAULT_REPORT_INCHES 0 // false
@@ -67,7 +67,7 @@
   #define DEFAULT_MM_PER_ARC_SEGMENT 0.1
   #define DEFAULT_RAPID_FEEDRATE 635.0 // mm/min (25ipm)
   #define DEFAULT_FEEDRATE 254.0 // mm/min (10ipm)
-  #define DEFAULT_ACCELERATION 50.0*60*60 // 50 mm/min^2
+  #define DEFAULT_ACCELERATION 50.0*60*60 // 50*60*60 mm/min^2 = 50 mm/s^2
   #define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
   #define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT))
   #define DEFAULT_REPORT_INCHES 1 // false
@@ -101,7 +101,7 @@
   #define DEFAULT_MM_PER_ARC_SEGMENT 0.1
   #define DEFAULT_RAPID_FEEDRATE 1000.0 // mm/min
   #define DEFAULT_FEEDRATE 250.0
-  #define DEFAULT_ACCELERATION (15.0*60*60) // 15 mm/min^2
+  #define DEFAULT_ACCELERATION (15.0*60*60) // 15*60*60 mm/min^2 = 15 mm/s^2
   #define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
   #define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT))
   #define DEFAULT_REPORT_INCHES 0 // false
@@ -135,7 +135,7 @@
   #define DEFAULT_MM_PER_ARC_SEGMENT 0.1
   #define DEFAULT_RAPID_FEEDRATE 800.0 // mm/min
   #define DEFAULT_FEEDRATE 250.0
-  #define DEFAULT_ACCELERATION (15.0*60*60) // 15 mm/min^2
+  #define DEFAULT_ACCELERATION (15.0*60*60) // 15*60*60 mm/min^2 = 15 mm/s^2
   #define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
   #define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT))
   #define DEFAULT_REPORT_INCHES 0 // false
@@ -168,7 +168,7 @@
   #define DEFAULT_MM_PER_ARC_SEGMENT 0.1
   #define DEFAULT_RAPID_FEEDRATE 2500.0 // mm/min
   #define DEFAULT_FEEDRATE 1000.0 // mm/min
-  #define DEFAULT_ACCELERATION 150.0*60*60 // 150 mm/min^2
+  #define DEFAULT_ACCELERATION 150.0*60*60 // 150*60*60 mm/min^2 = 150 mm/s^2
   #define DEFAULT_JUNCTION_DEVIATION 0.05 // mm
   #define DEFAULT_STEPPING_INVERT_MASK (1<<Y_DIRECTION_BIT)
   #define DEFAULT_REPORT_INCHES 0 // false
diff --git a/planner.c b/planner.c
index 7fc3e96..44248c4 100644
--- a/planner.c
+++ b/planner.c
@@ -393,7 +393,7 @@ void plan_buffer_line(float x, float y, float z, float feed_rate, uint8_t invert
   // average travel per step event changes. For a line along one axis the travel per step event
   // is equal to the travel/step in the particular axis. For a 45 degree line the steppers of both
   // axes might step for every step event. Travel per step event is then sqrt(travel_x^2+travel_y^2).
-  // To generate trapezoids with contant acceleration between blocks the rate_delta must be computed 
+  // To generate trapezoids with constant acceleration between blocks the rate_delta must be computed 
   // specifically for each line to compensate for this phenomenon:
   // Convert universal acceleration for direction-dependent stepper rate change parameter
   block->rate_delta = ceil( block->step_event_count*inverse_millimeters *