diff --git a/esphome/components/ota/ota_backend_esp8266.cpp b/esphome/components/ota/ota_backend_esp8266.cpp
index 1f9a77e426..93e6249fb3 100644
--- a/esphome/components/ota/ota_backend_esp8266.cpp
+++ b/esphome/components/ota/ota_backend_esp8266.cpp
@@ -105,6 +105,7 @@ OTAResponseTypes ESP8266OTABackend::begin(size_t image_size) {
 
   this->current_address_ = this->start_address_;
   this->image_size_ = image_size;
+  this->bytes_received_ = 0;
   this->buffer_len_ = 0;
   this->md5_set_ = false;
 
@@ -140,6 +141,7 @@ OTAResponseTypes ESP8266OTABackend::write(uint8_t *data, size_t len) {
     size_t to_buffer = std::min(len - written, this->buffer_size_ - this->buffer_len_);
     memcpy(this->buffer_.get() + this->buffer_len_, data + written, to_buffer);
     this->buffer_len_ += to_buffer;
+    this->bytes_received_ += to_buffer;
     written += to_buffer;
 
     // If buffer is full, write to flash
@@ -252,8 +254,8 @@ OTAResponseTypes ESP8266OTABackend::end() {
     }
   }
 
-  // Calculate actual bytes written
-  size_t actual_size = this->current_address_ - this->start_address_;
+  // Calculate actual bytes written (exact uploaded size, excluding flash write padding)
+  size_t actual_size = this->bytes_received_;
 
   // Check if any data was written
   if (actual_size == 0) {
@@ -304,6 +306,7 @@ void ESP8266OTABackend::abort() {
   this->buffer_.reset();
   this->buffer_len_ = 0;
   this->image_size_ = 0;
+  this->bytes_received_ = 0;
   esp8266::preferences_prevent_write(false);
 }
 
diff --git a/esphome/components/ota/ota_backend_esp8266.h b/esphome/components/ota/ota_backend_esp8266.h
index 6213289acc..b364e216a3 100644
--- a/esphome/components/ota/ota_backend_esp8266.h
+++ b/esphome/components/ota/ota_backend_esp8266.h
@@ -48,6 +48,7 @@ class ESP8266OTABackend final {
   uint32_t start_address_{0};
   uint32_t current_address_{0};
   size_t image_size_{0};
+  size_t bytes_received_{0};
 
   md5::MD5Digest md5_{};
   uint8_t expected_md5_[16];  // Fixed-size buffer for 128-bit (16-byte) MD5 digest