diff --git a/src/espmega_iot_emon.cpp b/src/espmega_iot_emon.cpp
index 2cb6054..863de9f 100644
--- a/src/espmega_iot_emon.cpp
+++ b/src/espmega_iot_emon.cpp
@@ -3,8 +3,8 @@
 ESPMega_CT::ESPMega_CT(uint8_t analog_pin, float (*adc_to_watts)(uint16_t adc_value), uint32_t fram_address)
 {
     this->analog_pin = analog_pin;
-    this->adc_to_watts = adc_to_watts;
     this->fram_address = fram_address;
+    this->adc_to_watts = adc_to_watts;
 }
 
 void ESPMega_CT::begin()
@@ -36,4 +36,18 @@ long double ESPMega_CT::get_energy()
 float ESPMega_CT::get_power()
 {
     return this->power;
+}
+
+float ESPMega_CT::adc_to_watts_builtin(uint16_t adc_value)
+{
+    const float RATIO = 0.1;
+    const float BURDEN_RESISTANCE = 20;
+    const float VOLTAGE = 220;
+    const uint16_t ADC_RANGE_START = 500;
+    const uint16_t ADC_RANGE_END = 16000;
+    const float ADC_RANGE = 12;
+    float burden_voltage = (adc_value - ADC_RANGE_START) / (ADC_RANGE_END - ADC_RANGE_START) * ADC_RANGE;
+    float secondary_current = burden_voltage / BURDEN_RESISTANCE;
+    float primary_current = secondary_current / RATIO;
+    return primary_current * VOLTAGE;
 }
\ No newline at end of file
diff --git a/src/espmega_iot_emon.hpp b/src/espmega_iot_emon.hpp
index e4993b8..818ce36 100644
--- a/src/espmega_iot_emon.hpp
+++ b/src/espmega_iot_emon.hpp
@@ -15,4 +15,5 @@ class ESPMega_CT {
         float power;
         long double energy;
         float (*adc_to_watts)(uint16_t adc_value);
+        float adc_to_watts_builtin(uint16_t adc_value);
 };
\ No newline at end of file