Reference

HX711 + Load Cell Weight Sensor Complete Guide

The HX711 is a 24-bit ADC purpose-built to amplify the tiny signal from a 4-wire load cell into something a microcontroller can read reliably. This guide covers the real wiring convention, which varies by manufacturer, and the calibration process every load cell genuinely needs, regardless of which specific one you bought.

21 september 2026 2 min read

A load cell is a strain gauge that outputs a microvolt-scale signal proportional to force, far too small and noisy for a microcontroller’s ADC to read directly. The HX711 is a dedicated 24-bit precision ADC that amplifies and digitizes that signal, then hands your microcontroller a clean number over a simple 2-wire protocol. This guide covers the HX711 module itself, not a specific load cell’s exact capacity, load cells range from a few hundred grams to several tonnes, and the wiring/calibration process below is the same regardless of which capacity you bought.

Pinout

Pin	Function
VCC	Power, 2.6V–5.5V
GND	Ground
DT (or DOUT)	Serial data output
SCK	Serial clock input
E+	Load cell excitation positive, to the load cell’s red wire
E−	Load cell excitation negative, to the load cell’s black wire
A+	Load cell signal positive, to the load cell’s white wire
A−	Load cell signal negative, to the load cell’s green wire

A 4-wire load cell’s color convention (red/black/white/green for excitation+/excitation−/signal+/signal−) is common but not universal, cheap load cells from different manufacturers sometimes swap white/green. If you accidentally swap the two signal wires, the reading just comes out with an inverted sign, harmless and fixable in your calibration factor, no need to re-wire.

Wiring to an ESP32

HX711 Pin	ESP32 Pin
VCC	3.3V
GND	GND
DT	GPIO4
SCK	GPIO5

DT and SCK can be any two free GPIOs, this protocol is bit-banged, not a hardware peripheral.

Arduino code (HX711 library by Bogdan Necula)

#include "HX711.h"

#define DT_PIN 4
#define SCK_PIN 5

HX711 scale;

void setup() {
  Serial.begin(115200);
  scale.begin(DT_PIN, SCK_PIN);
  scale.set_scale();       // reset until you calculate a real factor, see below
  scale.tare();            // zero the scale with nothing on it
}

void loop() {
  if (scale.is_ready()) {
    Serial.print("Weight: ");
    Serial.print(scale.get_units(10)); // average of 10 readings
    Serial.println(" units");
  }
  delay(200);
}

Install “HX711” (by Bogdan Necula) via the Arduino Library Manager.

Calibration (the part every load cell actually needs)

A load cell’s raw HX711 reading is meaningless until you calculate its calibration factor, and this step is unavoidable, every load cell, even two units of the exact same model, calibrates slightly differently.

With nothing on the scale, call scale.set_scale() (no argument) and scale.tare() to zero it.
Place an object of known weight (a kitchen scale, a labeled weight, anything with a known real mass) on the load cell.
Read the raw value with scale.get_units(10).
Calculate the calibration factor: raw_reading / known_weight.
Hard-code that factor into scale.set_scale(your_factor) in your real sketch.

Practical Applications

DIY kitchen/postal scales: the most common hobby use case.
Filament-level monitoring: track remaining 3D-printer filament by weight.
Plant/garden watering automation: trigger watering based on soil/pot weight.
Inventory/stock-level sensing: detect when a bin or container needs refilling.

Conclusion

The HX711 turns a load cell’s tiny, noisy analog signal into a clean, calibratable digital reading over a simple 2-wire bit-banged protocol, pairing easily with an ESP32 on any two free GPIOs.