diff --git a/esphome/components/ezo/ezo.cpp b/esphome/components/ezo/ezo.cpp
index 3c1b6e33e8..2ee5782ff6 100644
--- a/esphome/components/ezo/ezo.cpp
+++ b/esphome/components/ezo/ezo.cpp
@@ -79,7 +79,7 @@ void EZOSensor::loop() {
     if (buf[i] == ',')
       buf[i] = '\0';
 
-  float val = parse_number<float>((char *) &buf[1], sizeof(buf) - 2).value_or(0);
+  float val = parse_number<float>((char *) &buf[1]).value_or(0);
   this->publish_state(val);
 }
 
diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index 8b61e6aa38..208c555afd 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -370,9 +370,9 @@ std::string str_sanitize(const std::string &str);
 /// @name Parsing & formatting
 ///@{
 
-/// Parse an unsigned decimal number (requires null-terminated string).
+/// Parse an unsigned decimal number from a null-terminated string.
 template<typename T, enable_if_t<(std::is_integral<T>::value && std::is_unsigned<T>::value), int> = 0>
-optional<T> parse_number(const char *str, size_t len) {
+optional<T> parse_number(const char *str) {
   char *end = nullptr;
   unsigned long value = ::strtoul(str, &end, 10);  // NOLINT(google-runtime-int)
   if (end == str || *end != '\0' || value > std::numeric_limits<T>::max())
@@ -382,11 +382,11 @@ optional<T> parse_number(const char *str, size_t len) {
 /// Parse an unsigned decimal number.
 template<typename T, enable_if_t<(std::is_integral<T>::value && std::is_unsigned<T>::value), int> = 0>
 optional<T> parse_number(const std::string &str) {
-  return parse_number<T>(str.c_str(), str.length() + 1);
+  return parse_number<T>(str.c_str());
 }
-/// Parse a signed decimal number (requires null-terminated string).
+/// Parse a signed decimal number from a null-terminated string.
 template<typename T, enable_if_t<(std::is_integral<T>::value && std::is_signed<T>::value), int> = 0>
-optional<T> parse_number(const char *str, size_t len) {
+optional<T> parse_number(const char *str) {
   char *end = nullptr;
   signed long value = ::strtol(str, &end, 10);  // NOLINT(google-runtime-int)
   if (end == str || *end != '\0' || value < std::numeric_limits<T>::min() || value > std::numeric_limits<T>::max())
@@ -396,11 +396,10 @@ optional<T> parse_number(const char *str, size_t len) {
 /// Parse a signed decimal number.
 template<typename T, enable_if_t<(std::is_integral<T>::value && std::is_signed<T>::value), int> = 0>
 optional<T> parse_number(const std::string &str) {
-  return parse_number<T>(str.c_str(), str.length() + 1);
+  return parse_number<T>(str.c_str());
 }
-/// Parse a decimal floating-point number (requires null-terminated string).
-template<typename T, enable_if_t<(std::is_same<T, float>::value), int> = 0>
-optional<T> parse_number(const char *str, size_t len) {
+/// Parse a decimal floating-point number from a null-terminated string.
+template<typename T, enable_if_t<(std::is_same<T, float>::value), int> = 0> optional<T> parse_number(const char *str) {
   char *end = nullptr;
   float value = ::strtof(str, &end);
   if (end == str || *end != '\0' || value == HUGE_VALF)
@@ -410,7 +409,7 @@ optional<T> parse_number(const char *str, size_t len) {
 /// Parse a decimal floating-point number.
 template<typename T, enable_if_t<(std::is_same<T, float>::value), int> = 0>
 optional<T> parse_number(const std::string &str) {
-  return parse_number<T>(str.c_str(), str.length() + 1);
+  return parse_number<T>(str.c_str());
 }
 
 ///@}