diff --git a/main.c b/main.c
index ea63e40..b6c052b 100644
--- a/main.c
+++ b/main.c
@@ -547,6 +547,8 @@ properties_t current_props = {
     { 1, 30, 0 }, { 0, 40, 0 }, { 0, 60, 0 }, { 0, 80, 0 }
   },
   /* active_marker */      0,
+  /* domain_mode */        0,
+  /* velocity_factor */   70,
   /* checksum */           0
 };
 properties_t *active_props = &current_props;
diff --git a/nanovna.h b/nanovna.h
index e253113..d9e008f 100644
--- a/nanovna.h
+++ b/nanovna.h
@@ -299,6 +299,7 @@ typedef struct {
   marker_t _markers[4];
   int _active_marker;
   uint8_t _domain_mode;
+  uint8_t _velocity_factor; // %
 
   int32_t checksum;
 } properties_t;
@@ -323,6 +324,7 @@ extern int8_t previous_marker;
 #define markers current_props._markers
 #define active_marker current_props._active_marker
 #define domain_mode current_props._domain_mode
+#define velocity_factor current_props._velocity_factor
 
 int caldata_save(int id);
 int caldata_recall(int id);
diff --git a/plot.c b/plot.c
index ae44bf0..5fc7064 100644
--- a/plot.c
+++ b/plot.c
@@ -1373,7 +1373,7 @@ cell_draw_marker_info(int m, int n, int w, int h)
   } else {
 #define SPEED_OF_LIGHT 299792458
       float distance = ((float)idx * (float)SPEED_OF_LIGHT) / ( (float)(frequencies[1] - frequencies[0]) * 128.0 * 2.0);
-      chsnprintf(buf, sizeof buf, "%f m", distance);
+      chsnprintf(buf, sizeof buf, "%.1f m (%d%%)", distance * (velocity_factor / 100.0), velocity_factor);
       cell_drawstring_5x7(w, h, buf, xpos, ypos, 0xffff);
   }
 
diff --git a/ui.c b/ui.c
index 149bbd5..d62a54e 100644
--- a/ui.c
+++ b/ui.c
@@ -68,7 +68,7 @@ enum {
 };
 
 enum {
-  KM_START, KM_STOP, KM_CENTER, KM_SPAN, KM_CW, KM_SCALE, KM_REFPOS, KM_EDELAY
+  KM_START, KM_STOP, KM_CENTER, KM_SPAN, KM_CW, KM_SCALE, KM_REFPOS, KM_EDELAY, KM_VELOCITY_FACTOR
 };
 
 uint8_t ui_mode = UI_NORMAL;
@@ -667,23 +667,35 @@ menu_channel_cb(int item)
 static void
 menu_tdr_cb(int item)
 {
+  int status;
   switch (item) {
     case 0:
-        if ((domain_mode & DOMAIN_MODE) == DOMAIN_TIME) {
-            domain_mode = (domain_mode & ~DOMAIN_MODE) | DOMAIN_FREQ;
-        } else {
-            domain_mode = (domain_mode & ~DOMAIN_MODE) | DOMAIN_TIME;
-        }
+      if ((domain_mode & DOMAIN_MODE) == DOMAIN_TIME) {
+          domain_mode = (domain_mode & ~DOMAIN_MODE) | DOMAIN_FREQ;
+      } else {
+          domain_mode = (domain_mode & ~DOMAIN_MODE) | DOMAIN_TIME;
+      }
+      ui_mode_normal();
       break;
     case 1:
       domain_mode = (domain_mode & ~TDR_FUNC) | TDR_FUNC_IMPULSE;
+      ui_mode_normal();
       break;
     case 2:
       domain_mode = (domain_mode & ~TDR_FUNC) | TDR_FUNC_STEP;
+      ui_mode_normal();
+      break;
+    case 3:
+      status = btn_wait_release();
+      if (status & EVT_BUTTON_DOWN_LONG) {
+        ui_mode_numeric(KM_VELOCITY_FACTOR);
+        ui_process_numeric();
+      } else {
+        ui_mode_keypad(KM_VELOCITY_FACTOR);
+        ui_process_keypad();
+      }
       break;
   }
-
-  ui_mode_normal();
 }
 
 static void 
@@ -900,6 +912,7 @@ const menuitem_t menu_tdr[] = {
   { MT_CALLBACK, "TDR MODE", menu_tdr_cb },
   { MT_CALLBACK, "IMPULSE", menu_tdr_cb },
   { MT_CALLBACK, "STEP", menu_tdr_cb },
+  { MT_CALLBACK, "\2VELOCITY\0FACTOR", menu_tdr_cb },
   { MT_CANCEL, S_LARROW" BACK", NULL },
   { MT_NONE, NULL, NULL } // sentinel
 };
@@ -1150,11 +1163,12 @@ const keypads_t * const keypads_mode_tbl[] = {
   keypads_freq, // cw freq
   keypads_scale, // scale
   keypads_scale, // respos
-  keypads_time // electrical delay
+  keypads_time, // electrical delay
+  keypads_scale // velocity factor
 };
 
 const char * const keypad_mode_label[] = {
-  "START", "STOP", "CENTER", "SPAN", "CW FREQ", "SCALE", "REFPOS", "EDELAY"
+  "START", "STOP", "CENTER", "SPAN", "CW FREQ", "SCALE", "REFPOS", "EDELAY", "VELOCITY"
 };
 
 void
@@ -1402,6 +1416,9 @@ fetch_numeric_target(void)
   case KM_EDELAY:
     uistat.value = get_electrical_delay();
     break;
+  case KM_VELOCITY_FACTOR:
+    uistat.value = velocity_factor;
+    break;
   }
   
   {
@@ -1441,6 +1458,9 @@ void set_numeric_value(void)
   case KM_EDELAY:
     set_electrical_delay(uistat.value);
     break;
+  case KM_VELOCITY_FACTOR:
+    velocity_factor = uistat.value;
+    break;
   }
 }
 
@@ -1615,6 +1635,9 @@ keypad_click(int key)
     case KM_EDELAY:
       set_electrical_delay(value); // pico seconds
       break;
+    case KM_VELOCITY_FACTOR:
+      velocity_factor = value;
+      break;
     }
 
     return KP_DONE;