# Arduino Nano Guide Explore the Arduino Nano pinout, power options, specifications and versions, and learn how to use a Nano in electronics and custom PCB projects. Written by [Gabriel Hacohen](#) Published Oct 2026 - 10 min read ![Arduino Nano Guide](https://www.flux.ai/p/assets/blogs/arduino-nano-guide/main.webp) An Arduino Nano shows up in prototypes and small assemblies where a full-size Uno will not fit on the bench or inside the enclosure. Before wiring a Nano into a project, an engineer needs to understand the pin functions and power inputs. Version identification also matters because the Nano family now includes boards with different processors and logic levels. This guide uses the classic Arduino Nano, the original ATmega328P board, as the baseline for pinout and power. Later sections cover the newer Nano Every, Nano ESP32, and Nano R4 boards, and note where their pin functions or operating voltage diverge from the classic layout. ![A labeled pinout diagram of the classic Arduino Nano, showing its digital, analog, PWM, I2C, SPI, UART, and power pins across all 30 header positions.](https://www.flux.ai/p/assets/blogs/arduino-nano-guide/body-1-main.webp) A labeled pinout diagram of the classic Arduino Nano, showing its digital, analog, PWM, I2C, SPI, UART, and power pins across all 30 header positions. ## Key Takeaways - [The classic Arduino Nano](#what-is-an-arduino-nano) packs an ATmega328P processor and 8 analog inputs into a 45 x 18mm breadboard-friendly footprint. - [A Nano draws power from](#how-to-power-an-arduino-nano) USB, VIN, or a regulated 5V pin, and each path has its own voltage limits and failure points. - [The Nano Every, Nano ESP32, and Nano R4](#arduino-nano-versions-compared) share the classic form factor but differ in processor and logic voltage, so they are not automatic drop-in replacements. ### Classic Arduino Nano Specifications | **Spec** | **Value** | | --- | --- | | Processor | ATmega328P (8-bit AVR) | | Operating voltage | 5V | | Recommended input voltage (VIN) | 7-12V | | Digital I/O pins | 14 (6 PWM-capable) | | Analog inputs | 8 (A0-A7) | | PWM outputs | 6 (D3, D5, D6, D9, D10, D11) | | Flash memory | 32KB (2KB used by the bootloader) | | SRAM | 2KB | | Clock speed | 16MHz | | Communication interfaces | UART, SPI, I2C | | Dimensions | 45 x 18mm | ## What Is an Arduino Nano? The Arduino Nano is a compact, breadboard-friendly development board built around a microcontroller and the circuitry needed to run it: a voltage regulator, a USB-to-serial interface, and reset circuitry. Where the Uno spreads the same core electronics across a full-size PCB with a barrel jack and USB-B connector, the Nano fits it onto a card small enough to plug directly into a breadboard. ### Arduino Nano vs. Uno | **Attribute** | **Nano** | **Uno** | | --- | --- | --- | | Form factor | 45 x 18mm | 68.6 x 53.4mm | | Breadboard compatibility | Plugs in directly | Too wide for a standard breadboard | | USB connector | Mini-B, Micro-USB, USB-C (varies by version) | USB-B, USB-C (varies by version) | | External power connector | None (VIN pin only) | Barrel jack (2.1mm) | | Typical use | Space-constrained prototypes, permanent assemblies | Bench prototyping, shield-based projects | The size difference matters more than it looks: a Nano's pins sit on 0.1-inch centers along both long edges, so the board straddles a breadboard's center channel with every pin individually accessible. For a closer look at the larger board, see Flux's [Arduino Uno schematic diagram](https://www.flux.ai/p/blog/arduino-uno-schematic-diagram) and [Arduino Uno beginner's guide](https://www.flux.ai/p/blog/arduino-uno-basics-beginners-guide-to-getting-started). Or, for a broader comparison of Arduino board sizes and capabilities, see [how the Arduino Mega, Micro, and Uno differ](https://www.flux.ai/p/blog/what-is-the-real-difference-arduino-mega-vs-micro-vs-uno). ## Arduino Nano Pinout and Pin Functions The classic Arduino Nano exposes 30 pins across two rows for digital I/O, analog input, and dedicated communication interfaces. Each pin group has a distinct role in a schematic, and mixing them up is a common wiring mistake on a first build. Arduino publishes an official pinout diagram alongside the datasheet; the table below covers the same ground for quick reference. | **Pin group** | **Pins** | **Function** | | --- | --- | --- | | Digital I/O | D0-D13 | General-purpose input/output at 5V logic | | PWM | D3, D5, D6, D9, D10, D11 | Pulse-width modulation output, marked with a tilde | | Analog input | A0-A7 | 10-bit ADC inputs; A6 and A7 are analog-only | | I2C | A4 (SDA), A5 (SCL) | Two-wire interface for sensors and displays | | SPI | D10 (SS), D11 (MOSI), D12 (MISO), D13 (SCK) | Serial interface for devices that use a chip-select line | | UART | D0 (RX), D1 (TX) | Serial connection to a host computer or another microcontroller | | Reset | RESET | Pulled low to restart the board | | Analog reference | AREF | External reference voltage for the ADC | | Onboard LED | D13 | Built-in LED, shares the SPI clock pin | *SPI and the onboard LED both use D13, so a device wired to D13 for SPI communication makes the LED flicker during transfers, which is worth remembering when an SPI peripheral seems to work only intermittently.* **Keep in mind that pin functions are not identical across the Nano family.** - The Nano ESP32 runs 3.3V logic, is not 5V tolerant on its GPIO pins, and replaces the 5V pin with VBUS. - The Nano R4 keeps 5V logic but adds a CAN bus and a 12-bit DAC the classic board lacks. Confirm the pinout diagram for the exact board in hand before reusing a schematic built for a different Nano version. ## How to Power an Arduino Nano A Nano accepts power from three places: the USB connector, the VIN pin, and the 5V pin, and the board automatically selects whichever source supplies the higher voltage. Understanding each path prevents the handful of mistakes that damage more Nano boards than any other wiring error. ### Power Input Options - **USB:** regulated 5V, limited to roughly 500mA by an onboard polyfuse. - **VIN:** unregulated 7-12V (6-20V limit) feeding the onboard regulator, which steps it down to 5V. - **5V pin:** a regulated 5V input that bypasses the regulator, or an output when powered from USB or VIN. - **3.3V pin:** a secondary regulator output, good for up to about 50mA. VIN and the 5V pin are not interchangeable. VIN expects unregulated voltage above 5V, since it still passes through the onboard regulator. The 5V pin sits after that regulator and needs an already-regulated source; it will not tolerate the higher voltages VIN accepts. ### Common Arduino Nano Power Mistakes - **Feeding regulated 5V into VIN:** falls below the regulator's dropout voltage, leaving the board under-powered and unreliable. - **Exceeding the regulator's output current:** it dissipates the VIN-to-5V difference as heat, so a high VIN with a current-hungry load can overheat it well below rated output. - **Powering external components from 5V or 3.3V:** motors and relays need their own supply; the onboard regulator is sized for light peripheral loads. - **Connecting 5V signals to a 3.3V Nano variant:** the Nano ESP32 needs a level shifter for any sensor built around the classic Nano's 5V logic. - **Combining supplies without isolation:** VIN and USB together is fine, since the board picks the higher source, but two regulated supplies tied to the 5V pin risk a current fight. ## Arduino Nano Versions Compared Four boards currently carry the Nano name, and they share a footprint more than they share silicon. Matching the processor, logic voltage, and memory to the project matters more than matching the board's shape. | **Board** | **Processor** | **Logic voltage** | **Wireless** | **Flash / SRAM** | **Clock speed** | **Best for** | | --- | --- | --- | --- | --- | --- | --- | | Classic Nano | ATmega328P (8-bit AVR) | 5V | None | 32KB / 2KB | 16MHz | Legacy compatibility, low cost | | Nano Every | ATmega4809 (8-bit AVR) | 5V | None | 48KB / 6KB | 20MHz | More memory, same pinout and voltage | | Nano ESP32 | ESP32-S3 (dual-core Xtensa LX7) | 3.3V | Wi-Fi + Bluetooth 5 | 16MB / 512KB (+8MB PSRAM) | Up to 240MHz | IoT projects needing onboard wireless | | [Nano R4](https://www.flux.ai/p/blog/meet-the-arduino-nano-r4-why-is-this-tiny-upgrade-so-big-for-makers) | Renesas RA4M1 (Arm Cortex-M4) | 5V | None | 256KB / 32KB | 48MHz | 32-bit processing, CAN bus, DAC | Pin compatibility stops at the physical footprint. All four boards share the same 30-pin layout and 0.1-inch spacing, so a carrier PCB designed for one physically accepts any of them. Electrical compatibility is separate: a shield built for the classic Nano's 5V logic can damage a Nano ESP32's 3.3V GPIO pins, and [code written for the classic Arduino](https://www.flux.ai/p/blog/arduino-code-a-comprehensive-guide-for-beginners) Nano's pin assignments needs an adjusted board definition before it runs on the ATmega4809 or RA4M1 boards. The AVR-based boards run simpler 8-bit instruction sets, while the [ESP32](https://www.flux.ai/p/blog/esp32-pinout-everything-you-need-to-know) and R4 use 32-bit cores that handle heavier code faster. ### Choosing a Nano Version - **Classic compatibility, lowest cost:** the original Nano, for reproducing an existing 5V design. - **More memory, same voltage:** the Nano Every, once sketches outgrow 2KB of SRAM. - **Wireless connectivity:** the Nano ESP32, for Wi-Fi or Bluetooth without a separate radio module. - **32-bit processing, extra peripherals:** the Nano R4, for CAN bus, a built-in DAC, or headroom beyond 8-bit AVR. - **Low idle power draw:** the classic Nano, or an ESP32 board's deep-sleep modes if wireless is still needed. ## Using Arduino Nano in Projects and Custom PCBs A Nano moves through several stages between a first prototype and a finished product, and each stage changes how the board should be mounted. Breadboard prototypes use the header pins directly. Permanent assemblies often solder wires straight to the board or use a socketed carrier that stays swappable for repairs. Custom PCB projects mount the Nano as a module, either socketed or soldered flush with castellated edges. ### Design Considerations for a Nano Carrier Board - **Schematic placement:** place the Nano as one schematic symbol rather than redrawing the ATmega328P, and verify every symbol pin maps to the correct physical pin. - **Header spacing and orientation:** match the 0.1-inch pitch and keep the USB connector and reset button on an accessible edge. - **USB connector access:** leave clearance around the connector (Mini-B, Micro-USB, or USB-C) so a cable can seat without hitting an enclosure wall. - **Reset-button access:** add a cutout or external reset button if the onboard one will be covered once mounted. - **Power and decoupling:** add a bulk capacitor near VIN and a bypass capacitor near the 5V and 3.3V pins. - **Mechanical clearance:** check the USB connector and crystal height against anything mounted directly above. - **Antenna clearance:** on the Nano ESP32, keep copper pours and shielding away from the module's antenna area. Flux supports each step directly: 1. **Select** a Nano module from a shared component library. 2. **Place** it into a schematic, then let footprint validation confirm the symbol matches the physical part before routing. 3. **Run** design rule checks and DFM review to catch header spacing or clearance problems before fabrication, when they are far cheaper to fix than after boards return from a fab house. ## Bringing an Arduino Nano into Your Next PCB An Arduino Nano earns its place in a design once the pinout, power path, and version are locked in. From there, the remaining work is turning a breadboard prototype into a board that survives outside the lab. Flux keeps that transition in one place: a shared component library for the Nano module, footprint validation, and DFM review before a carrier PCB goes to fabrication. [Start a Nano-based PCB project in Flux](https://www.flux.ai/p). ## FAQs ### What is an Arduino Nano used for? An Arduino Nano suits compact embedded projects such as sensor logging, small robotics, and wearables, where a full-size Uno would not fit. ### Is the Arduino Nano a 5V or 3.3V board? The classic Nano, Nano Every, and Nano R4 run 5V logic, while the Nano ESP32 runs 3.3V logic and does not tolerate 5V signals on the board's GPIO pins. ### What is the difference between Arduino Nano and Uno? The Arduino Nano uses a smaller 45 x 18mm footprint with no barrel jack, while the Uno spreads the same electronics across a larger board with a USB-B connector and barrel jack. ### Can an Arduino Nano replace an Arduino Uno? A classic Arduino Nano can run most Uno sketches, since both share the ATmega328P processor, but shields built for the Uno's header layout need an adapter to fit the Nano. ### How do you power an Arduino Nano? An Arduino Nano can be powered through USB, through VIN with an unregulated 7-12V source, or through the 5V pin with an already-regulated supply. ### Do all Arduino Nano boards have the same pinout? All current Nano boards share the same 30-pin footprint, but pin functions, logic voltage, and interfaces differ across the classic Nano, Nano Every, Nano ESP32, and Nano R4. ### Which Arduino Nano version should I use? Version choice depends on the project: the classic Nano suits legacy 5V designs, the Nano Every adds memory, the Nano ESP32 adds wireless, and the Nano R4 adds 32-bit processing and CAN bus. ## About the author Gabriel Hacohen Electronics Engineer at Flux Gabriel Hacohen is an electrical engineer with deep expertise in analog circuitry, medical devices, high-performance computing, and semiconductors. He holds both Bachelor's and Master's degrees in Electrical Engineering and has written for companies including NVIDIA, Cadence, Synopsys, Netflix, and Autodesk. 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