diff --git a/esphome/components/nau7802/nau7802.cpp b/esphome/components/nau7802/nau7802.cpp
index acdca03fdb..6a31b754f7 100644
--- a/esphome/components/nau7802/nau7802.cpp
+++ b/esphome/components/nau7802/nau7802.cpp
@@ -218,7 +218,7 @@ void NAU7802Sensor::dump_config() {
 
 void NAU7802Sensor::write_value_(uint8_t start_reg, size_t size, int32_t value) {
   uint8_t data[4];
-  for (int i = 0; i < size; i++) {
+  for (size_t i = 0; i < size; i++) {
     data[i] = 0xFF & (value >> (size - 1 - i) * 8);
   }
   this->write_register(start_reg, data, size);
@@ -228,7 +228,7 @@ int32_t NAU7802Sensor::read_value_(uint8_t start_reg, size_t size) {
   uint8_t data[4];
   this->read_register(start_reg, data, size);
   int32_t result = 0;
-  for (int i = 0; i < size; i++) {
+  for (size_t i = 0; i < size; i++) {
     result |= data[i] << (size - 1 - i) * 8;
   }
   // extend sign bit