diff --git a/ports/espressif/supervisor/port.c b/ports/espressif/supervisor/port.c
index 78c3508458..8d10c1f7dc 100644
--- a/ports/espressif/supervisor/port.c
+++ b/ports/espressif/supervisor/port.c
@@ -102,22 +102,6 @@ static size_t spiram_size_usable(void) {
 }
 #endif
 
-// Heap sizes for when there is no external RAM for CircuitPython to use
-// exclusively.
-#ifdef CONFIG_IDF_TARGET_ESP32
-// TODO: Determine better: 520kB of internal RAM; similar to 512kB for ESP32-S3.
-#define HEAP_SIZE (88 * 1024)
-#endif
-#ifdef CONFIG_IDF_TARGET_ESP32S2
-#define HEAP_SIZE (48 * 1024)
-#endif
-#ifdef CONFIG_IDF_TARGET_ESP32S3
-#define HEAP_SIZE (176 * 1024)
-#endif
-#ifdef CONFIG_IDF_TARGET_ESP32C3
-#define HEAP_SIZE (88 * 1024)
-#endif
-
 uint32_t *heap;
 uint32_t heap_size;
 
@@ -231,8 +215,10 @@ safe_mode_t port_init(void) {
     #endif
 
     if (heap == NULL) {
-        heap = malloc(HEAP_SIZE);
-        heap_size = HEAP_SIZE / sizeof(uint32_t);
+        size_t heap_total = heap_caps_get_total_size(MALLOC_CAP_8BIT);
+        heap_size = MIN(heap_caps_get_largest_free_block(MALLOC_CAP_8BIT), heap_total / 2);
+        heap = malloc(heap_size);
+        heap_size = heap_size / sizeof(uint32_t);
     }
     if (heap == NULL) {
         heap_size = 0;