| Arduino Uno R3 | Arduino Nano | |
|---|---|---|
| Chip | ATmega328P, 16 MHz | ATmega328P, 16 MHz |
| Flash / SRAM / EEPROM | 32 KB / 2 KB / 1 KB | 32 KB / 2 KB / 1 KB |
| Analog inputs | 6 (A0–A5) | 8 (A6 and A7 are analog-only) |
| USB | USB-B (large square plug) | Mini-USB on most; USB-C on some clones |
| Power input | DC barrel jack or VIN, 7–12 V | VIN pin, 7–12 V (no jack) |
| Board size | 68.6 × 53.4 mm | About 18 × 45 mm |
| Shields | Plug straight on | Needs an expansion board |
| Typical price in India | ₹450–800 clone · ₹2,000+ genuine | ₹250–400 clone |
Same ATmega328P, same speed, same memory, same code. Any sketch for one runs on the other after you change the board in Tools. The choice is about shape and convenience. Figures are from the official Arduino documentation; prices are indicative.
Choose the Uno for…
- Learning. Big labelled headers, sturdy, and every beginner kit’s diagrams use it. Our 30-day path starts on the Uno.
- Shields. Motor, relay, Ethernet and LCD keypad shields plug straight on.
- Power from an adapter. The barrel jack takes a 9–12 V adapter directly.
Hub: Arduino Uno R3.
Choose the Nano for…
- Breadboards. It plugs straight in, with pins on both sides of the centre gap.
- Finished builds. Small enough for a project box, a robot chassis or a wearable.
- Two extra analog inputs (A6, A7), handy for more sensors — but they can’t be used as digital pins.
- Lower cost per project, so it can stay inside the build.
Hub: Arduino Nano.
Clone quirks in India
- Nano clones mostly need Tools → Processor → ATmega328P (Old Bootloader), or uploads fail with “not in sync” (fix).
- Both usually have a CH340 USB chip — install its driver if no port appears (fix).
- Genuine boards use different USB chips and the new bootloader; they’re worth it if you want to support the Arduino project.
What about the Uno R4?
The newer Uno R4 Minima and R4 WiFi keep the Uno shape but use a 32-bit Renesas RA4M1 (48 MHz, 256 KB flash, 32 KB RAM); the R4 WiFi adds an ESP32-S3 for Wi-Fi. Most beginner sketches run unchanged, but libraries written specifically for the AVR chip may not. They cost more than clones — consider an ESP32 if Wi-Fi is the reason.
Verdict
Learning or using shields → Uno. Breadboard or finished project → Nano. Many makers learn on an Uno and then buy a few Nanos for builds. For battery-powered builds, also look at the Pro Mini.