Arduino Nano pinout

A small, breadboard-friendly Arduino with the same chip as the Uno. It uses 5 V logic, so 3.3 V-only sensors need a level shifter.

Top view, USB connector on the left. Colors: red power, grey ground, green GPIO, yellow analog, orange USB serial, blue I2C.

BoardPilot showing the Arduino Nano in 3D

Try it live

The real app with a simulated Arduino Nano, running in your browser. No install, nothing to plug in.

At a glance

Chip: ATmega328P
Processor: 8-bit AVR ATmega328P at 16 MHz, 2 KB SRAM, 32 KB flash, 1 KB EEPROM
Logic level: 5 V. 3.3 V-only sensors need a level shifter.
Flashing tool: avrdude
Arduino board (FQBN): arduino:avr:nano
Live pin view in BoardPilot: Yes (diagnostic agent available)

Pins to avoid or use with care

Input only: A6 (ADC6), A7 (ADC7)

Cannot drive outputs, and have no internal pull-up.

USB serial: RX0 (PD0), TX1 (PD1)

Used for uploading and the serial monitor. Anything connected here can break uploads.

Good pins for LEDs, buttons and signals

D2, D3, D4, D5, D6, D7, D8, D9

Default pins in Arduino

I2C: SDA = A4, SCL = A5. Only these pins work with the Wire library defaults. I2C only works on A4 (SDA) and A5 (SCL).
SPI: MOSI = D11, MISO = D12, SCK = D13, CS = D10.
Analog inputs: A0, A1, A2, A3, A6, A7, A4, A5 (0–5 V)

How to flash it

Clones with the old bootloader upload at 57600 baud: choose “ATmega328P (Old Bootloader)” if uploads fail.

All 30 pins

Pin	GPIO	Chip pin	Functions	Notes
D12	12	PB4	GPIO, SPI_MISO (default)
D11	11	PB3	GPIO, PWM, SPI_MOSI (default)
D10	10	PB2	GPIO, PWM, SPI_CS (default)	SPI chip select. Keep it an OUTPUT when using SPI, or SPI can stop working.
D9	9	PB1	GPIO, PWM
D8	8	PB0	GPIO
D7	7	PD7	GPIO
D6	6	PD6	GPIO, PWM
D5	5	PD5	GPIO, PWM
D4	4	PD4	GPIO
D3	3	PD3	GPIO, INT1, PWM
D2	2	PD2	GPIO, INT0
GND	—
RST	—		RESET	Reset input. Pull it LOW (or press the button) to restart the board.
RX0	0	PD0	GPIO, UART0_RX	Serial RX. Shared with the USB link: using it for parts can break uploads and the serial monitor.
TX1	1	PD1	GPIO, UART0_TX	Serial TX. Shared with the USB link: using it for parts can break uploads and the serial monitor.
D13	13	PB5	GPIO, SPI_SCK (default)	The built-in LED "L" is on this pin (also SPI clock).
3V3	—			3.3 V from the USB chip (FT232RL, 50 mA max; often less on clones). Weak: fine for one small sensor only.
REF	—		ADC_REF	Analog reference input. Leave it unconnected unless your code calls analogReference(EXTERNAL); never power parts from it.
A0	14	PC0	GPIO, ADC0
A1	15	PC1	GPIO, ADC1
A2	16	PC2	GPIO, ADC2
A3	17	PC3	GPIO, ADC3
A4	18	PC4	GPIO, ADC4, I2C_SDA (default)	Default I2C SDA (same signal as the SDA pin).
A5	19	PC5	GPIO, ADC5, I2C_SCL (default)	Default I2C SCL (same signal as the SCL pin).
A6	20	ADC6	ADC6	Analog input only: no digitalWrite, no digitalRead and no internal pull-up.
A7	21	ADC7	ADC7	Analog input only: no digitalWrite, no digitalRead and no internal pull-up.
5V	—			5 V output from USB or the on-board regulator.
RST	—		RESET	Reset input. Pull it LOW (or press the button) to restart the board.
GND	—
VIN	—			Power input (7-12 V recommended) from the barrel jack or an external supply. It is not fed from USB, so do not use it to power parts.

Questions

Which pins are I2C on the Arduino Nano?

SDA is A4 and SCL is A5 (the defaults of the Arduino Wire library). Only certain pins support I2C in hardware, so use these unless you know your core allows others.

Which Arduino Nano pins should I avoid?

RX0, TX1 (USB serial link); A6, A7 (input only).

Is the Arduino Nano 5 V tolerant?

The Arduino Nano runs at 5 V, so 5 V sensors connect directly. 3.3 V-only parts need a level shifter.

Which pins can read analog voltage on the Arduino Nano?

A0, A1, A2, A3, A6, A7, A4, A5, from 0 to 5 V.

How do I upload code to the Arduino Nano?

In the Arduino IDE pick the board arduino:avr:nano (core arduino:avr). Clones with the old bootloader upload at 57600 baud: choose “ATmega328P (Old Bootloader)” if uploads fail.