diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index 58f162ff9d..c3b404ae60 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -783,7 +783,7 @@ template<class T> class RAMAllocator {
   T *reallocate(T *p, size_t n) { return this->reallocate(p, n, sizeof(T)); }
 
   T *reallocate(T *p, size_t n, size_t manual_size) {
-    size_t size = n * sizeof(T);
+    size_t size = n * manual_size;
     T *ptr = nullptr;
 #ifdef USE_ESP32
     if (this->flags_ & Flags::ALLOC_EXTERNAL) {