diff --git a/config.gen3.h b/config.gen3.h
index cf1b9a5..15a192b 100644
--- a/config.gen3.h
+++ b/config.gen3.h
@@ -129,10 +129,9 @@
 */
 #define ACCELERATION_RAMPING
 
-/// how fast to accelerate when using ACCELERATION_RAMPING
-/// smaller values give quicker acceleration
-/// valid range = 1 to 8,000,000; 500,000 is a good starting point
-#define ACCELERATION_STEEPNESS	500000
+/// how fast to accelerate when using ACCELERATION_RAMPING, given in mm/s^2
+/// decimal allowed, useful range 1. to 10'000, typical range 10. to 100.
+#define ACCELERATION 10.
 
 /** \def ACCELERATION_TEMPORAL
 	temporal step algorithm
diff --git a/config.gen6.h b/config.gen6.h
index 0d8a9ba..f344b5e 100644
--- a/config.gen6.h
+++ b/config.gen6.h
@@ -128,10 +128,9 @@
 */
 #define ACCELERATION_RAMPING
 
-/// how fast to accelerate when using ACCELERATION_RAMPING
-/// smaller values give quicker acceleration
-/// valid range = 1 to 8,000,000; 500,000 is a good starting point
-#define ACCELERATION_STEEPNESS	500000
+/// how fast to accelerate when using ACCELERATION_RAMPING, given in mm/s^2
+/// decimal allowed, useful range 1. to 10'000, typical range 10. to 100.
+#define ACCELERATION 10.
 
 /** \def ACCELERATION_TEMPORAL
 	temporal step algorithm
diff --git a/config.h.dist b/config.h.dist
index 1ce136a..2a6cf15 100644
--- a/config.h.dist
+++ b/config.h.dist
@@ -126,10 +126,9 @@
 */
 #define ACCELERATION_RAMPING
 
-/// how fast to accelerate when using ACCELERATION_RAMPING
-/// smaller values give quicker acceleration
-/// valid range = 1 to 8,000,000; 500,000 is a good starting point
-#define ACCELERATION_STEEPNESS	500000
+/// how fast to accelerate when using ACCELERATION_RAMPING, given in mm/s^2
+/// decimal allowed, useful range 1. to 10'000, typical range 10. to 100.
+#define ACCELERATION 10.
 
 /** \def ACCELERATION_TEMPORAL
 	temporal step algorithm
diff --git a/config.ramps.h b/config.ramps.h
index 2d68b9a..781ae93 100644
--- a/config.ramps.h
+++ b/config.ramps.h
@@ -133,10 +133,9 @@
 */
 #define ACCELERATION_RAMPING
 
-/// how fast to accelerate when using ACCELERATION_RAMPING
-/// smaller values give quicker acceleration
-/// valid range = 1 to 8,000,000; 500,000 is a good starting point
-#define ACCELERATION_STEEPNESS	500000
+/// how fast to accelerate when using ACCELERATION_RAMPING, given in mm/s^2
+/// decimal allowed, useful range 1. to 10'000, typical range 10. to 100.
+#define ACCELERATION 10.
 
 /** \def ACCELERATION_TEMPORAL
 	temporal step algorithm
diff --git a/dda.c b/dda.c
index 4f68d33..e776ad5 100644
--- a/dda.c
+++ b/dda.c
@@ -6,6 +6,7 @@
 
 #include	<string.h>
 #include	<stdlib.h>
+#include	<math.h>
 #include	<avr/interrupt.h>
 
 #include	"timer.h"
@@ -335,8 +336,13 @@ void dda_create(DDA *dda, TARGET *target) {
 		// add the last bit of dda->total_steps to always round up
 			dda->ramp_steps = dda->total_steps / 2 + (dda->total_steps & 1);
 			dda->step_no = 0;
-			// c is initial step time in IOclk ticks
-			dda->c = ACCELERATION_STEEPNESS << 8;
+// remove this when people have swallowed the new config item
+#ifdef ACCELERATION_STEEPNESS
+#error ACCELERATION_STEEPNESS is gone, review your config.h and use ACCELERATION
+#endif
+			// c is initial step time in IOclk ticks (currently, IOclk ticks = F_CPU)
+			// yes, this assumes always the x axis as the critical one regarding acceleration. If we want to implement per-axis acceleration, things get tricky ...
+			dda->c = ((uint32_t)((double)F_CPU / sqrt((double)(STEPS_PER_MM_X * ACCELERATION)))) << 8;
 			dda->c_min = (move_duration / target->F) << 8;
 			if (dda->c_min < c_limit)
 				dda->c_min = c_limit;