Raspberry Pi GPIO Pinout

Raspberry Pi GPIO pinout — BCM numbers, physical pins, and alternate functions

The Raspberry Pi 40-pin GPIO header gives you access to digital I/O, PWM, SPI, I2C, UART, and power rails — but remembering which physical pin maps to which BCM number is something even experienced Pi users look up constantly. This interactive reference lets you switch between a grid view for quick function lookup and a physical header view that mirrors the actual pin layout on the board, so you can confidently wire up sensors and peripherals without counting pins on your Pi.

BCM vs physical (BOARD) pin numbering

Raspberry Pi GPIO has two numbering schemes. Physical (BOARD) numbering counts pins 1–40 from top-left to bottom-right of the 40-pin header as it sits on the board. BCM numbering follows the Broadcom chip's internal GPIO numbers, which are not sequential. Most software libraries (RPi.GPIO, gpiozero, pigpio) default to BCM numbering. In Python: GPIO.setmode(GPIO.BCM) uses BCM numbers; GPIO.setmode(GPIO.BOARD) uses physical positions. This reference shows both, so you can use either mode without confusion.

Key GPIO functions and which pins support them

I2C (GPIO 2 = SDA, GPIO 3 = SCL) connects sensors and displays using just two wires — common devices include BME280 temperature/humidity sensors, MPU6050 accelerometers, and SSD1306 OLED displays. SPI (GPIO 10 = MOSI, GPIO 9 = MISO, GPIO 11 = SCLK, GPIO 8/7 = CE0/CE1) is used for fast peripherals like SD cards, high-speed ADCs, and LoRa radio modules. UART (GPIO 14 = TXD, GPIO 15 = RXD) is used for serial communication with GPS modules, Arduino boards, and GSM modems. Hardware PWM is available on GPIO 12, 13, 18, 19 — software PWM is possible on any GPIO but produces jitter.

Voltage levels and current limits

All Raspberry Pi GPIO pins operate at 3.3 V logic — not 5 V tolerant. Connecting a 5 V signal directly to a GPIO input will damage the Pi. Use a logic level converter or a voltage divider (two resistors) to step 5 V Arduino signals down to 3.3 V. Each GPIO pin can source or sink a maximum of 16 mA, with a recommended maximum of 8 mA per pin for sustained use. The total current draw across all GPIO pins should not exceed 50 mA. For driving LEDs, always use a current-limiting resistor (330 Ω for a standard red LED on 3.3 V).

Compatible across Raspberry Pi models

The 40-pin GPIO header layout is consistent across Raspberry Pi 2, 3, 4, 5, and Zero/Zero 2 W. The original Model B and A had a 26-pin header (the first 26 pins are the same). This reference covers the full 40-pin standard used on all modern Pi boards. The Pi 5 introduced changes to the low-level GPIO implementation (using the new RP1 southbridge chip), so some timing-sensitive code may need adjustment, but the pin assignments remain the same.