diff --git a/esphome/components/online_image/bmp_image.cpp b/esphome/components/online_image/bmp_image.cpp
index f55c9f1813..676a2efca9 100644
--- a/esphome/components/online_image/bmp_image.cpp
+++ b/esphome/components/online_image/bmp_image.cpp
@@ -117,7 +117,8 @@ int HOT BmpDecoder::decode(uint8_t *buffer, size_t size) {
         this->paint_index_++;
         this->current_index_ += 3;
         index += 3;
-        if (x == this->width_ - 1 && this->padding_bytes_ > 0) {
+        size_t last_col = static_cast<size_t>(this->width_) - 1;
+        if (x == last_col && this->padding_bytes_ > 0) {
           index += this->padding_bytes_;
           this->current_index_ += this->padding_bytes_;
         }
diff --git a/esphome/components/online_image/jpeg_image.cpp b/esphome/components/online_image/jpeg_image.cpp
index e5ee3dd8bf..10586091d5 100644
--- a/esphome/components/online_image/jpeg_image.cpp
+++ b/esphome/components/online_image/jpeg_image.cpp
@@ -25,8 +25,10 @@ static int draw_callback(JPEGDRAW *jpeg) {
   // to avoid crashing.
   App.feed_wdt();
   size_t position = 0;
-  for (size_t y = 0; y < jpeg->iHeight; y++) {
-    for (size_t x = 0; x < jpeg->iWidth; x++) {
+  size_t height = static_cast<size_t>(jpeg->iHeight);
+  size_t width = static_cast<size_t>(jpeg->iWidth);
+  for (size_t y = 0; y < height; y++) {
+    for (size_t x = 0; x < width; x++) {
       auto rg = decode_value(jpeg->pPixels[position++]);
       auto ba = decode_value(jpeg->pPixels[position++]);
       Color color(rg[1], rg[0], ba[1], ba[0]);