Safe GPIO pins
Use 5 V logic and the documented maximum of 20 mA per GPIO. VIN is recommended at 7–12 V. The silicon’s 40 mA absolute limit is not an operating-current target.
Embedded hardware reference for engineers and makers
Arduino Nano Classic Pinout & Reference
36-pin interactive pinoutThe Arduino Nano Classic is a compact, breadboard-friendly board based on the ATmega328P. It provides identical computing capability to the Uno in a DIP-30 footprint with 2 extra analog inputs.
- Arduino
- Verified source
- Updated Oct 2026
- GPIO
- Power
- Ground
- Analog
- Control
- Bus
Tap a row of pins to see it up close
Arduino Nano Classic
ATmega328P
- MCU
- ATmega328P
- CPU core
- 8-bit AVR RISC
- Clock speed
- 16 MHz
- SRAM
- 2 KB
- Flash
- 32 KB
- GPIO count
- 20
- Logic voltage
- 5.0 V
- Form factor
- 36-pin, USB-to-serial (FT232RL on Nano V3.3)
Before you wire
5 V logic — level-shift 3.3 V peripherals
- Confirm connected peripherals are compatible with 5 V logic.
- Use A6 and A7 only as analog inputs.
- Respect the documented AREF voltage and analog-reference configuration.
QUICK LINKS
Pin table
Showing 36 of 36 pins| Pin | Name | GPIO | Functions | ADC | Default role | Flags |
|---|---|---|---|---|---|---|
| 1 left | D1 / TX | GPIO1 | gpiouart | — | GPIO | Wired to the USB-UART bridge |
| 2 left | D0 / RX | GPIO0 | gpiouart | — | GPIO | Wired to the USB-UART bridge |
| 3 left | RESET | — | reset | — | Reset / Enable | |
| 4 left | GND | — | gnd | — | Ground | |
| 5 left | D2 | GPIO2 | gpio | — | GPIO | |
| 6 left | ~D3 | GPIO3 | gpiopwm | — | GPIO | |
| 7 left | D4 | GPIO4 | gpio | — | GPIO | |
| 8 left | ~D5 | GPIO5 | gpiopwm | — | GPIO | |
| 9 left | ~D6 | GPIO6 | gpiopwm | — | GPIO | |
| 10 left | D7 | GPIO7 | gpio | — | GPIO | |
| 11 left | D8 | GPIO8 | gpio | — | GPIO | |
| 12 left | ~D9 | GPIO9 | gpiopwm | — | GPIO | |
| 13 left | ~D10 / SS | GPIO10 | gpiospipwm | — | GPIO | |
| 14 left | ~D11 / MOSI | GPIO11 | gpiospipwm | — | GPIO | |
| 15 left | D12 / MISO | GPIO12 | gpiospi | — | GPIO | |
| 30 right | VIN | — | power | — | 7.0–12.0 V Power | |
| 29 right | GND | — | gnd | — | Ground | |
| 28 right | RESET | — | reset | — | Reset / Enable | |
| 27 right | +5V | — | power | — | 5.0 V Power | |
| 26 right | A7 | — | adc | ADC7 | GPIO | Input only |
| 25 right | A6 | — | adc | ADC6 | GPIO | Input only |
| 24 right | A5 / SCL | GPIO19 | gpioi2cadc | ADC5 | GPIO | |
| 23 right | A4 / SDA | GPIO18 | gpioi2cadc | ADC4 | GPIO | |
| 22 right | A3 | GPIO17 | gpioadc | ADC3 | GPIO | |
| 21 right | A2 | GPIO16 | gpioadc | ADC2 | GPIO | |
| 20 right | A1 | GPIO15 | gpioadc | ADC1 | GPIO | |
| 19 right | A0 | GPIO14 | gpioadc | ADC0 | GPIO | |
| 18 right | AREF | — | input | — | GPIO | External reference voltage limits |
| 17 right | 3V3 | — | power | — | 3.3 V Power | |
| 16 right | D13 / SCK | GPIO13 | gpiospi | — | GPIO | Shared with an onboard component |
| icsp:1 icsp | MISO | GPIO12 | gpiospiicsp | — | GPIO | |
| icsp:2 icsp | +5V | — | power | — | 5.0 V Power | |
| icsp:3 icsp | SCK | GPIO13 | gpiospiicsp | — | GPIO | |
| icsp:4 icsp | MOSI | GPIO11 | gpiospipwmicsp | — | GPIO | |
| icsp:5 icsp | RESET | — | reset | — | Reset / Enable | |
| icsp:6 icsp | GND | — | power | — | 0 V Power |
Grounded reference
Board overview
Arduino Nano Classic is a compact, breadboard-friendly ATmega328P board with 5 V logic, Mini-B USB, and two additional analog-only inputs compared with the Uno.
Canonical CAD Blueprint
The model depicts the Nano V3.3 board without fitted pin headers with FT232RL, Mini-B USB and a 5 × 5 mm ATmega328P-MUR package. Its 30 main contacts and six ICSP contacts are CAD-grounded. Fitted headers, USB bridges and MCU packages vary on compatible boards.
Power inputs
- Mini-B USB provides the board 5 V supply and serial programming connection.
- VIN accepts an external unregulated 7–12 V supply through the onboard regulator.
- The 5V pin connects to the regulated 5 V board rail.
Hardware Variants, Clones & Traps
- Select ATmega328P for current official Nano boards; pre-2018 boards may need ATmega328P (Old Bootloader). The official core uses 115200 and 57600 baud respectively.
- The reference board uses FT232RL. CH340 or USB-C derivatives may need different drivers and have different power circuits; check their schematic.
- The reference MCU is ATmega328P-MUR in QFN32. Other package variants exist; ATmega168 derivatives need the corresponding processor selection and have less flash.
- Nano Every, Nano 33 and Nano ESP32 are separate boards. Confirm their MCU, logic levels and pin allocation before reusing Classic wiring.
Common use cases
- Compact breadboard prototypes and sensor interfaces.
- Small robots, controllers, and permanent embedded installations.
- Embedded programming and electronics education.
Notes
- The ATmega328P and exposed digital I/O use 5 V logic.
- A6 and A7 are analog-input-only pins and cannot operate as digital GPIO.
- The board specifies at most 20 mA per GPIO. Observe the MCU’s 200 mA VCC/GND aggregate and port-group budgets. Its 40 mA absolute limit must not be used as a normal load.
Before you wire
- Confirm connected peripherals are compatible with 5 V logic.
- Use A6 and A7 only as analog inputs.
- Respect the documented AREF voltage and analog-reference configuration.
Specifications
- MCU
- ATmega328P
- CPU core
- 8-bit AVR RISC
- Clock
- 16 MHz
- SRAM
- 2 KB
- Flash
- 0.03125 MB
- GPIO count
- 20
- Logic voltage
- 5.0 V
- Operating voltage (VIN)
- 7 - 12 V
Primary sources
Arduino Nano full pinout, pp1–3ATmega328P 8-bit AVR Microcontroller DatasheetArduino Nano V3.3 schematicNanoV3.3 Eagle board and schematicArduinoCore-avr eightanaloginputs variant and inherited standard mappingFT232R manufacturer datasheet (SparkFun-hosted mirror)Select the right processor for Arduino NanoATmega48A/PA/88A/PA/168A/PA/328/P Silicon ErrataPin usage guide
ADC and analog pins
Pins A0-A7 provide 8 channels of 10-bit ADC. Note: A6 and A7 are dedicated analog inputs and cannot be used as digital GPIO.
I2C, SPI and UART pins
UART on pin 1 (TX) and pin 2 (RX). SPI on D10 (SS), D11 (MOSI), D12 (MISO), D13 (SCK) plus ICSP. I2C on pin 23 (A4/SDA) and pin 24 (A5/SCL).
Strapping and boot pins
Standard AVR architecture. D13 drives the onboard L LED.
Input-only pins
D0–D13 and A0–A5 are bidirectional GPIO with internal pull-ups. D0/D1 share the FT232RL serial connection; D13 drives L. A6/A7 are analog-only and have no GPIO pull-ups.
Frequently asked questions
Short answers to the questions people ask about this board, each checked against the manufacturer or project documents linked under it.
Can Nano A6 and A7 be used as digital pins?
A6 and A7 are dedicated analog inputs with no digital output or GPIO pull-up. A0–A5 also work as digital GPIO. There are eight ADC inputs in total; AREF is a reference pin, not a ninth channel.
Which bootloader setting should I use for Nano Classic?
For official boards sold from 2018 onward, select Arduino Nano and ATmega328P. Older boards may need ATmega328P (Old Bootloader); the official upload rates are 115200 and 57600 baud respectively. Some third-party boards use ATmega168, so check the MCU marking.
How much current can Nano supply?
The full pinout specifies at most 20 mA per GPIO and 50 mA from the authentic FT232RL-derived 3V3 output. The MCU’s 40 mA absolute per-I/O limit and 200 mA VCC/GND aggregate are not normal load targets; port-group limits also apply. Available 5 V output depends on input voltage, regulator heating and the board’s own load.
Help keep this page accurate
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