diff --git a/dda.c b/dda.c
index e946c95..868fe3c 100644
--- a/dda.c
+++ b/dda.c
@@ -360,8 +360,8 @@ void dda_create(DDA *dda, TARGET *target) {
 
       // Acceleration ramps are based on the fast axis, not the combined speed.
       dda->rampup_steps =
-        ACCELERATE_RAMP_LEN_SPM(muldiv(dda->fast_um, dda->endpoint.F, distance),
-                                dda->fast_spm);
+        acc_ramp_len(muldiv(dda->fast_um, dda->endpoint.F, distance),
+                     dda->fast_spm);
 
       if (dda->rampup_steps > dda->total_steps / 2)
         dda->rampup_steps = dda->total_steps / 2;
diff --git a/dda_maths.c b/dda_maths.c
index 6e66f61..908ce59 100644
--- a/dda_maths.c
+++ b/dda_maths.c
@@ -235,3 +235,21 @@ const uint8_t msbloc (uint32_t v) {
   }
   return 0;
 }
+
+/*! Acceleration ramp length in steps.
+ * \param feedrate Target feedrate of the accelerateion.
+ * \param steps_per_m Steps/m of the axis.
+ * \return Accelerating steps neccessary to achieve target feedrate.
+ *
+ * s = 1/2 * a * t^2, v = a * t ==> s = v^2 / (2 * a)
+ * 7200000 = 60 * 60 * 1000 * 2 (mm/min -> mm/s, steps/m -> steps/mm, factor 2)
+ *
+ * Note: this function has shown to be accurate between 10 and 10'000 mm/s2 and
+ *       2000 to 4096000 steps/m (and higher). The numbers are a few percent
+ *       too high at very low acceleration. Test code see commit message.
+ */
+uint32_t acc_ramp_len(uint32_t feedrate, uint32_t steps_per_m) {
+  return (feedrate * feedrate) /
+         (((uint32_t)7200000UL * ACCELERATION) / steps_per_m);
+}
+
diff --git a/dda_maths.h b/dda_maths.h
index 192ccd1..901e648 100644
--- a/dda_maths.h
+++ b/dda_maths.h
@@ -66,14 +66,9 @@ uint16_t int_inv_sqrt(uint16_t a);
 // 2 ^ msbloc(v) >= v
 const uint8_t msbloc (uint32_t v);
 
-// s = 1/2 * a * t^2, v = a * t ==> s = v^2 / (2 * a)
-// 7200000 = 60 * 60 * 1000 * 2 (mm/min -> mm/s, steps/m -> steps/mm, factor 2)
-// Note: this macro has shown to be accurate between 10 and 10'000 mm/s2 and
-//       2000 to 4096000 steps/m (and higher). The numbers are a few percent
-//       too high at very low acceleration. Test code see commit message.
-#define ACCELERATE_RAMP_LEN_SPM(speed, spm)        \
-  (((speed) * (speed)) /                           \
-  (uint32_t)((7200000UL * ACCELERATION) / (spm)))
+// Calculates acceleration ramp length in steps.
+uint32_t acc_ramp_len(uint32_t feedrate, uint32_t steps_per_m);
+
 // For X axis only, should become obsolete:
 #define ACCELERATE_RAMP_LEN(speed) (((speed)*(speed)) / (uint32_t)((7200000.0f * ACCELERATION) / (float)STEPS_PER_M_X))