diff --git a/Marlin/src/Marlin.cpp b/Marlin/src/Marlin.cpp
index ccd32a465..873e046bb 100644
--- a/Marlin/src/Marlin.cpp
+++ b/Marlin/src/Marlin.cpp
@@ -159,9 +159,6 @@ bool axis_homed[XYZ] = { false }, axis_known_position[XYZ] = { false };
   TempUnit input_temp_units = TEMPUNIT_C;
 #endif
 
-// Initialized by settings.load()
-float filament_size[EXTRUDERS], volumetric_multiplier[EXTRUDERS];
-
 #if FAN_COUNT > 0
   int16_t fanSpeeds[FAN_COUNT] = { 0 };
   #if ENABLED(PROBING_FANS_OFF)
@@ -336,16 +333,6 @@ void quickstop_stepper() {
 
 #endif // FILAMENT_RUNOUT_SENSOR
 
-float calculate_volumetric_multiplier(const float diameter) {
-  if (!parser.volumetric_enabled || diameter == 0) return 1.0;
-  return 1.0 / (M_PI * sq(diameter * 0.5));
-}
-
-void calculate_volumetric_multipliers() {
-  for (uint8_t i = 0; i < COUNT(filament_size); i++)
-    volumetric_multiplier[i] = calculate_volumetric_multiplier(filament_size[i]);
-}
-
 void enable_all_steppers() {
   enable_X();
   enable_Y();
diff --git a/Marlin/src/Marlin.h b/Marlin/src/Marlin.h
index 97e80c5db..e8e42d4f8 100644
--- a/Marlin/src/Marlin.h
+++ b/Marlin/src/Marlin.h
@@ -174,9 +174,6 @@ extern bool Running;
 inline bool IsRunning() { return  Running; }
 inline bool IsStopped() { return !Running; }
 
-extern float filament_size[EXTRUDERS]; // cross-sectional area of filament (in millimeters), typically around 1.75 or 2.85, 0 disables the volumetric calculations for the extruder.
-extern float volumetric_multiplier[EXTRUDERS]; // reciprocal of cross-sectional area of filament (in square millimeters), stored this way to reduce computational burden in planner
-
 extern bool axis_known_position[XYZ];
 extern bool axis_homed[XYZ];
 extern volatile bool wait_for_heatup;
@@ -223,8 +220,6 @@ extern millis_t max_inactive_time, stepper_inactive_time;
   extern int lpq_len;
 #endif
 
-void calculate_volumetric_multipliers();
-
 bool pin_is_protected(const int8_t pin);
 
 #endif // __MARLIN_H__
diff --git a/Marlin/src/feature/fwretract.cpp b/Marlin/src/feature/fwretract.cpp
index 421761b66..029a11c41 100644
--- a/Marlin/src/feature/fwretract.cpp
+++ b/Marlin/src/feature/fwretract.cpp
@@ -124,7 +124,7 @@ void FWRetract::retract(const bool retracting
 
     // Retract by moving from a faux E position back to the current E position
     feedrate_mm_s = retract_feedrate_mm_s;
-    current_position[E_AXIS] += (swapping ? swap_retract_length : retract_length) / volumetric_multiplier[active_extruder];
+    current_position[E_AXIS] += (swapping ? swap_retract_length : retract_length) / planner.volumetric_multiplier[active_extruder];
     sync_plan_position_e();
     prepare_move_to_destination();
 
@@ -149,7 +149,7 @@ void FWRetract::retract(const bool retracting
     feedrate_mm_s = swapping ? swap_retract_recover_feedrate_mm_s : retract_recover_feedrate_mm_s;
 
     const float move_e = swapping ? swap_retract_length + swap_retract_recover_length : retract_length + retract_recover_length;
-    current_position[E_AXIS] -= move_e / volumetric_multiplier[active_extruder];
+    current_position[E_AXIS] -= move_e / planner.volumetric_multiplier[active_extruder];
     sync_plan_position_e();
 
     prepare_move_to_destination();  // Recover E
diff --git a/Marlin/src/gcode/config/M200.cpp b/Marlin/src/gcode/config/M200.cpp
index b70879fc4..081171638 100644
--- a/Marlin/src/gcode/config/M200.cpp
+++ b/Marlin/src/gcode/config/M200.cpp
@@ -22,6 +22,7 @@
 
 #include "../gcode.h"
 #include "../../Marlin.h"
+#include "../../module/planner.h"
 
 /**
  * M200: Set filament diameter and set E axis units to cubic units
@@ -37,13 +38,8 @@ void GcodeSuite::M200() {
     // setting any extruder filament size disables volumetric on the assumption that
     // slicers either generate in extruder values as cubic mm or as as filament feeds
     // for all extruders
-    parser.volumetric_enabled = (parser.value_linear_units() != 0.0);
-    if (parser.volumetric_enabled) {
-      filament_size[target_extruder] = parser.value_linear_units();
-      // make sure all extruders have some sane value for the filament size
-      for (uint8_t i = 0; i < COUNT(filament_size); i++)
-        if (! filament_size[i]) filament_size[i] = DEFAULT_NOMINAL_FILAMENT_DIA;
-    }
+    if ( (parser.volumetric_enabled = (parser.value_linear_units() != 0.0)) )
+      planner.set_filament_size(target_extruder, parser.value_linear_units());
   }
-  calculate_volumetric_multipliers();
+  planner.calculate_volumetric_multipliers();
 }
diff --git a/Marlin/src/gcode/feature/filwidth/M404-M407.cpp b/Marlin/src/gcode/feature/filwidth/M404-M407.cpp
index 42ac9b622..4a811056e 100644
--- a/Marlin/src/gcode/feature/filwidth/M404-M407.cpp
+++ b/Marlin/src/gcode/feature/filwidth/M404-M407.cpp
@@ -76,7 +76,7 @@ void GcodeSuite::M405() {
  */
 void GcodeSuite::M406() {
   filament_sensor = false;
-  calculate_volumetric_multipliers();   // Restore correct 'volumetric_multiplier' value
+  planner.calculate_volumetric_multipliers();   // Restore correct 'volumetric_multiplier' value
 }
 
 /**
diff --git a/Marlin/src/lcd/ultralcd.cpp b/Marlin/src/lcd/ultralcd.cpp
index e4bbf0044..386b8aa9b 100644
--- a/Marlin/src/lcd/ultralcd.cpp
+++ b/Marlin/src/lcd/ultralcd.cpp
@@ -3442,20 +3442,20 @@ void kill_screen(const char* lcd_msg) {
       MENU_ITEM_EDIT(float3, MSG_ADVANCE_K, &planner.extruder_advance_k, 0, 999);
     #endif
 
-    MENU_ITEM_EDIT_CALLBACK(bool, MSG_VOLUMETRIC_ENABLED, &parser.volumetric_enabled, calculate_volumetric_multipliers);
+    MENU_ITEM_EDIT_CALLBACK(bool, MSG_VOLUMETRIC_ENABLED, &parser.volumetric_enabled, planner.calculate_volumetric_multipliers);
 
     if (parser.volumetric_enabled) {
       #if EXTRUDERS == 1
-        MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(float43, MSG_FILAMENT_DIAM, &filament_size[0], 1.5, 3.25, calculate_volumetric_multipliers);
+        MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(float43, MSG_FILAMENT_DIAM, &planner.filament_size[0], 1.5, 3.25, planner.calculate_volumetric_multipliers);
       #else // EXTRUDERS > 1
-        MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(float43, MSG_FILAMENT_DIAM MSG_DIAM_E1, &filament_size[0], 1.5, 3.25, calculate_volumetric_multipliers);
-        MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(float43, MSG_FILAMENT_DIAM MSG_DIAM_E2, &filament_size[1], 1.5, 3.25, calculate_volumetric_multipliers);
+        MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(float43, MSG_FILAMENT_DIAM MSG_DIAM_E1, &planner.filament_size[0], 1.5, 3.25, planner.calculate_volumetric_multipliers);
+        MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(float43, MSG_FILAMENT_DIAM MSG_DIAM_E2, &planner.filament_size[1], 1.5, 3.25, planner.calculate_volumetric_multipliers);
         #if EXTRUDERS > 2
-          MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(float43, MSG_FILAMENT_DIAM MSG_DIAM_E3, &filament_size[2], 1.5, 3.25, calculate_volumetric_multipliers);
+          MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(float43, MSG_FILAMENT_DIAM MSG_DIAM_E3, &planner.filament_size[2], 1.5, 3.25, planner.calculate_volumetric_multipliers);
           #if EXTRUDERS > 3
-            MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(float43, MSG_FILAMENT_DIAM MSG_DIAM_E4, &filament_size[3], 1.5, 3.25, calculate_volumetric_multipliers);
+            MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(float43, MSG_FILAMENT_DIAM MSG_DIAM_E4, &planner.filament_size[3], 1.5, 3.25, planner.calculate_volumetric_multipliers);
             #if EXTRUDERS > 4
-              MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(float43, MSG_FILAMENT_DIAM MSG_DIAM_E5, &filament_size[4], 1.5, 3.25, calculate_volumetric_multipliers);
+              MENU_MULTIPLIER_ITEM_EDIT_CALLBACK(float43, MSG_FILAMENT_DIAM MSG_DIAM_E5, &planner.filament_size[4], 1.5, 3.25, planner.calculate_volumetric_multipliers);
             #endif // EXTRUDERS > 4
           #endif // EXTRUDERS > 3
         #endif // EXTRUDERS > 2
diff --git a/Marlin/src/lcd/ultralcd_impl_DOGM.h b/Marlin/src/lcd/ultralcd_impl_DOGM.h
index 6f01e2997..963d2022b 100644
--- a/Marlin/src/lcd/ultralcd_impl_DOGM.h
+++ b/Marlin/src/lcd/ultralcd_impl_DOGM.h
@@ -637,7 +637,7 @@ static void lcd_implementation_status_screen() {
     strcpy(zstring, ftostr52sp(FIXFLOAT(current_position[Z_AXIS])));
     #if ENABLED(FILAMENT_LCD_DISPLAY) && DISABLED(SDSUPPORT)
       strcpy(wstring, ftostr12ns(filament_width_meas));
-      strcpy(mstring, itostr3(100.0 * volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]));
+      strcpy(mstring, itostr3(100.0 * planner.volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]));
     #endif
   }
 
@@ -726,7 +726,7 @@ static void lcd_implementation_status_screen() {
         lcd_print(ftostr12ns(filament_width_meas));
         lcd_printPGM(PSTR("  " LCD_STR_FILAM_MUL));
         u8g.print(':');
-        lcd_print(itostr3(100.0 * volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]));
+        lcd_print(itostr3(100.0 * planner.volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]));
         u8g.print('%');
       }
     #else
diff --git a/Marlin/src/lcd/ultralcd_impl_HD44780.h b/Marlin/src/lcd/ultralcd_impl_HD44780.h
index 9f6982968..cf25fe64f 100644
--- a/Marlin/src/lcd/ultralcd_impl_HD44780.h
+++ b/Marlin/src/lcd/ultralcd_impl_HD44780.h
@@ -853,7 +853,7 @@ static void lcd_implementation_status_screen() {
       lcd_printPGM(PSTR("Dia "));
       lcd.print(ftostr12ns(filament_width_meas));
       lcd_printPGM(PSTR(" V"));
-      lcd.print(itostr3(100.0 * volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]));
+      lcd.print(itostr3(100.0 * planner.volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]));
       lcd.write('%');
       return;
     }
diff --git a/Marlin/src/module/configuration_store.cpp b/Marlin/src/module/configuration_store.cpp
index f48106741..e32ce4fa7 100644
--- a/Marlin/src/module/configuration_store.cpp
+++ b/Marlin/src/module/configuration_store.cpp
@@ -138,7 +138,7 @@
  *
  * Volumetric Extrusion:                            21 bytes
  *  537  M200 D    parser.volumetric_enabled        (bool)
- *  538  M200 T D  filament_size                    (float x5) (T0..3)
+ *  538  M200 T D  planner.filament_size            (float x5) (T0..3)
  *
  * HAVE_TMC2130:                                    20 bytes
  *  558  M906 X    Stepper X current                (uint16_t)
@@ -224,7 +224,7 @@ void MarlinSettings::postprocess() {
     thermalManager.updatePID();
   #endif
 
-  calculate_volumetric_multipliers();
+  planner.calculate_volumetric_multipliers();
 
   #if HAS_HOME_OFFSET || ENABLED(DUAL_X_CARRIAGE)
     // Software endstops depend on home_offset
@@ -509,7 +509,7 @@ void MarlinSettings::postprocess() {
 
     // Save filament sizes
     for (uint8_t q = 0; q < MAX_EXTRUDERS; q++) {
-      if (q < COUNT(filament_size)) dummy = filament_size[q];
+      if (q < COUNT(planner.filament_size)) dummy = planner.filament_size[q];
       EEPROM_WRITE(dummy);
     }
 
@@ -895,7 +895,7 @@ void MarlinSettings::postprocess() {
 
       for (uint8_t q = 0; q < MAX_EXTRUDERS; q++) {
         EEPROM_READ(dummy);
-        if (q < COUNT(filament_size)) filament_size[q] = dummy;
+        if (q < COUNT(planner.filament_size)) planner.filament_size[q] = dummy;
       }
 
       uint16_t val;
@@ -1260,8 +1260,8 @@ void MarlinSettings::reset() {
       false
     #endif
   ;
-  for (uint8_t q = 0; q < COUNT(filament_size); q++)
-    filament_size[q] = DEFAULT_NOMINAL_FILAMENT_DIA;
+  for (uint8_t q = 0; q < COUNT(planner.filament_size); q++)
+    planner.filament_size[q] = DEFAULT_NOMINAL_FILAMENT_DIA;
 
   endstops.enable_globally(
     #if ENABLED(ENDSTOPS_ALWAYS_ON_DEFAULT)
@@ -1388,23 +1388,23 @@ void MarlinSettings::reset() {
     }
 
     CONFIG_ECHO_START;
-    SERIAL_ECHOPAIR("  M200 D", filament_size[0]);
+    SERIAL_ECHOPAIR("  M200 D", planner.filament_size[0]);
     SERIAL_EOL();
     #if EXTRUDERS > 1
       CONFIG_ECHO_START;
-      SERIAL_ECHOPAIR("  M200 T1 D", filament_size[1]);
+      SERIAL_ECHOPAIR("  M200 T1 D", planner.filament_size[1]);
       SERIAL_EOL();
       #if EXTRUDERS > 2
         CONFIG_ECHO_START;
-        SERIAL_ECHOPAIR("  M200 T2 D", filament_size[2]);
+        SERIAL_ECHOPAIR("  M200 T2 D", planner.filament_size[2]);
         SERIAL_EOL();
         #if EXTRUDERS > 3
           CONFIG_ECHO_START;
-          SERIAL_ECHOPAIR("  M200 T3 D", filament_size[3]);
+          SERIAL_ECHOPAIR("  M200 T3 D", planner.filament_size[3]);
           SERIAL_EOL();
           #if EXTRUDERS > 4
             CONFIG_ECHO_START;
-            SERIAL_ECHOPAIR("  M200 T4 D", filament_size[4]);
+            SERIAL_ECHOPAIR("  M200 T4 D", planner.filament_size[4]);
             SERIAL_EOL();
           #endif // EXTRUDERS > 4
         #endif // EXTRUDERS > 3
diff --git a/Marlin/src/module/planner.cpp b/Marlin/src/module/planner.cpp
index f906f769e..0373f342c 100644
--- a/Marlin/src/module/planner.cpp
+++ b/Marlin/src/module/planner.cpp
@@ -105,6 +105,10 @@ float Planner::max_feedrate_mm_s[XYZE_N], // Max speeds in mm per second
 
 int16_t Planner::flow_percentage[EXTRUDERS] = ARRAY_BY_EXTRUDERS1(100); // Extrusion factor for each extruder
 
+// Initialized by settings.load()
+float Planner::filament_size[EXTRUDERS],         // As a baseline for the multiplier, filament diameter
+      Planner::volumetric_multiplier[EXTRUDERS]; // May be auto-adjusted by a filament width sensor
+
 uint32_t Planner::max_acceleration_steps_per_s2[XYZE_N],
          Planner::max_acceleration_mm_per_s2[XYZE_N]; // Use M201 to override by software
 
@@ -539,6 +543,16 @@ void Planner::check_axes_activity() {
   #endif
 }
 
+inline float calculate_volumetric_multiplier(const float &diameter) {
+  if (!parser.volumetric_enabled || diameter == 0) return 1.0;
+  return 1.0 / CIRCLE_AREA(diameter * 0.5);
+}
+
+void Planner::calculate_volumetric_multipliers() {
+  for (uint8_t i = 0; i < COUNT(filament_size); i++)
+    volumetric_multiplier[i] = calculate_volumetric_multiplier(filament_size[i]);
+}
+
 #if PLANNER_LEVELING
   /**
    * lx, ly, lz - logical (cartesian, not delta) positions in mm
diff --git a/Marlin/src/module/planner.h b/Marlin/src/module/planner.h
index 5cd886431..def50dbb8 100644
--- a/Marlin/src/module/planner.h
+++ b/Marlin/src/module/planner.h
@@ -151,6 +151,10 @@ class Planner {
 
     static int16_t flow_percentage[EXTRUDERS];  // Extrusion factor for each extruder
 
+    static float filament_size[EXTRUDERS],          // diameter of filament (in millimeters), typically around 1.75 or 2.85, 0 disables the volumetric calculations for the extruder
+                 volumetric_multiplier[EXTRUDERS];  // Reciprocal of cross-sectional area of filament (in mm^2). Pre-calculated to reduce computation in the planner
+                                                    // May be auto-adjusted by a filament width sensor
+
     static float max_feedrate_mm_s[XYZE_N],     // Max speeds in mm per second
                  axis_steps_per_mm[XYZE_N],
                  steps_to_mm[XYZE_N];
@@ -254,6 +258,16 @@ class Planner {
 
     static bool is_full() { return (block_buffer_tail == BLOCK_MOD(block_buffer_head + 1)); }
 
+    // Update multipliers based on new diameter measurements
+    static void calculate_volumetric_multipliers();
+
+    FORCE_INLINE static void set_filament_size(const uint8_t e, const float &v) {
+      filament_size[e] = v;
+      // make sure all extruders have some sane value for the filament size
+      for (uint8_t i = 0; i < COUNT(filament_size); i++)
+        if (!filament_size[i]) filament_size[i] = DEFAULT_NOMINAL_FILAMENT_DIA;
+    }
+
     #if PLANNER_LEVELING
 
       #define ARG_X float lx
diff --git a/Marlin/src/module/temperature.cpp b/Marlin/src/module/temperature.cpp
index 03cce00f7..7ff161950 100644
--- a/Marlin/src/module/temperature.cpp
+++ b/Marlin/src/module/temperature.cpp
@@ -775,7 +775,7 @@ void Temperature::manage_heater() {
       // Get the delayed info and add 100 to reconstitute to a percent of
       // the nominal filament diameter then square it to get an area
       const float vmroot = measurement_delay[meas_shift_index] * 0.01 + 1.0;
-      volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM] = vmroot <= 0.1 ? 0.01 : sq(vmroot);
+      planner.volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM] = vmroot <= 0.1 ? 0.01 : sq(vmroot);
     }
   #endif // FILAMENT_WIDTH_SENSOR