Arduino Nano vs Uno: Differences, Specs & Which to Choose (2025)

Both the Arduino Nano and Uno use the same ATmega328P microcontroller at 16 MHz. The differences are form factor, size, price, and a few I/O details. Here's everything you need to decide which one to buy.

Quick answer: Nano for compact projects and breadboard use. Uno for learning, shields, and classroom environments.

Arduino Nano vs Uno: Specs Comparison

The Key Difference: Form Factor

The Uno is 3× larger than the Nano. That's the main reason to choose one over the other.

Arduino Nano (18 × 45 mm):

• Fits directly on a breadboard — pins straddle both sides
• Ideal for finished projects where size matters
• Harder to connect shields (no standard shield headers)

Arduino Uno (53 × 68 mm):

• Uses screw-on headers for shields
• Easier for beginners to wire
• Standard in classrooms and tutorials

I/O Differences That Matter

The Nano has 8 analog inputs (A0–A7), the Uno has only 6 (A0–A5). The Nano's extra A6 and A7 pins are analog input only — they cannot be used as digital I/O.

Both boards have the same 6 PWM-capable pins (3, 5, 6, 9, 10, 11).

The Nano also exposes more digital pins (22 vs 14) in the same size package.

USB Connector and Drivers

Arduino Uno: Uses USB Type-B (the large square printer plug) and the official ATmega16U2 USB-to-serial chip. Drivers install automatically on Windows 10+ and macOS.

Arduino Nano: Uses Mini-USB or Micro-USB (depending on revision) and typically the CH340 chip on clones. You may need to install CH340 drivers on Windows.

This is the most common issue beginners face with Nano clones — the board isn't recognized until CH340 drivers are installed.

Bootloader and Programming

Both boards use the same bootloader (Arduino Optiboot for the ATmega328P) and are programmed identically in Arduino IDE:

• Select Tools → Board → Arduino Nano or Arduino Uno
• For Nano clones with CH340: Select Processor → ATmega328P (Old Bootloader)

The code you write is 100% compatible — same setup(), same loop(), same library calls. A sketch written for Uno runs on Nano without any changes (and vice versa).

Power Options

Both boards output regulated 5V and 3.3V. The Uno's barrel jack makes it easier to use with wall adapters.

Shield Compatibility

Arduino Uno: Full shield compatibility. Shields (motor drivers, display shields, SD card shields, Ethernet shields) plug directly onto the Uno's standard headers.

Arduino Nano: Not shield compatible. The Nano uses a different pin layout. However, Nano expansion boards (breakout boards) exist that convert the Nano to Uno-style headers.

If you rely on shields: choose the Uno.

Which to Choose?

Choose Arduino Nano if:

• Your project must fit in a small enclosure
• You're building something permanent (soldered into a PCB)
• You need 8 analog inputs
• You're an experienced user who doesn't need shields
• Budget is tight (clones are cheaper)

Choose Arduino Uno if:

• You're a beginner learning electronics
• You use shields (motor drivers, displays, etc.)
• You follow online tutorials (most use Uno diagrams)
• You're teaching a class or workshop
• You need easier wiring with breadboard jumpers

Both are identical for:

• Processing power (same chip, same speed)
• Code compatibility (same sketch runs on both)
• Library support (same libraries work on both)
• Wireless capabilities (neither has WiFi/BT built in)

Tip: If you eventually want WiFi or Bluetooth, consider moving to ESP32 instead. It's faster, has more memory, and wireless is built in — for a similar price to an Arduino Uno clone.

Arduino Nano vs Uno vs ESP32 — Quick Summary

Frequently Asked Questions (FAQ)

Is Arduino Nano the same as Arduino Uno? They run the same ATmega328P chip at 16 MHz with the same flash/RAM. The differences are size (Nano is 3× smaller), connector type, and the number of analog pins (8 on Nano vs 6 on Uno).

Can I use the same code on both Arduino Nano and Uno? Yes. Code written for one runs on the other without modification. Pin numbers are the same.

Why won't my Arduino Nano be detected on my computer? Most Nano clones use the CH340 USB chip instead of the ATmega16U2. Install the CH340 drivers for your OS. Also, in Arduino IDE, select "ATmega328P (Old Bootloader)" under Processor.

Is Arduino Nano better than Uno? Neither is objectively better — they serve different use cases. Nano for compact or permanent projects. Uno for learning and shield-based projects.

Can Arduino Nano use Uno shields? Not directly. Nano uses a different header layout. You can use a Nano expansion board that adapts the pinout to Uno-compatible headers.

What is the difference between Arduino Nano and Arduino Nano Every? The Nano Every uses an ATmega4809 (not ATmega328P), has more flash (48 KB vs 32 KB), more SRAM (6 KB vs 2 KB), and costs more. It's not fully pin-compatible — some shields don't work.

Arduino Nano vs Uno: which is cheaper? Nano clones start at ~$2 USD. Uno clones start at ~$4 USD. Genuine boards from Arduino: Nano ~$22, Uno ~$27.

Projects Reference

• Ohm's Law Calculator — Resistor calculations for your Arduino circuits
• LED Series Resistor Calculator — Calculate current-limiting resistors
• Wokwi Simulator Guide — Simulate both boards online for free
• ESP32 vs Arduino — Full comparison if you're considering ESP32