# Arduino UNO R3

> Classic 5 V Arduino: ATmega328P (DIP) at 16 MHz, 32 KB flash, 2 KB SRAM, 1 KB EEPROM, 14 digital I/O (6 PWM), 6 analog inputs, USB-B via ATmega16U2, 2.1 mm DC jack 6–20 V.

- Manufacturer: Arduino S.r.l
- Part number: A000066
- Category: Development boards
- Canonical page: https://www.xirkit.io/products/arduino-uno-r3-9ffd
- Pinout: https://www.xirkit.io/products/arduino-uno-r3-9ffd/pinout
- Structured JSON: https://www.xirkit.io/products/arduino-uno-r3-9ffd/data.json
- Source: Xirkit structured parts catalog — every value traced to a cited document; unknowns are explicit.

## Key specifications

| Property | Value |
| --- | --- |
| Main chip | ATmega328P |
| Chips on board | ATmega328P |
| Exposed GPIO | 20 |
| Documented board pins | 32 |
| I/O voltage | 5 V |
| Supply voltage | 1–20 V |
| Flash | 32 KB |
| SRAM | 2 KB |
| Interfaces | gpio, control, interrupt, adc, i2c, uart, pwm, timer, analog_comparator, clock, spi, led, usb |
| Frameworks | Arduino IDE, Arduino Cloud Editor |
| Dimensions | 68.58 × 53.34 mm |
| Operating temperature | -40 to 85 °C |
| Certifications | CE, RoHS, REACH |

## Pinout (32 pins, 23 with electrical limits)

| Pin | Position | Kind | Chip pad | Functions | VIH | VIL | VOH | VOL | IOH | IOL | 5 V tolerant |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| NC | JANALOG · 1 | nc | — | no_connect | — | — | — | — | — | — | — |
| IOREF | JANALOG · 2 | power out | — | power_out | — | — | — | — | — | — | — |
| RESET | JANALOG · 3 | control | PC6 | PC6, RESET, PCINT14 | 4.5–5.5 V | -0.5–0.5 V | — | — | — | — | yes |
| +3V3 | JANALOG · 4 | power out | — | power_out | — | — | — | — | — | — | — |
| +5V | JANALOG · 5 | power out | — | power_out | — | — | — | — | — | — | — |
| GND | JANALOG · 6 | ground | — | ground | — | — | — | — | — | — | — |
| GND | JANALOG · 7 | ground | — | ground | — | — | — | — | — | — | — |
| VIN | JANALOG · 8 | power in | — | power_in | — | — | — | — | — | — | — |
| A0 | JANALOG · 9 | gpio | PC0 | D14, PC0, ADC0, PCINT8 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| A1 | JANALOG · 10 | gpio | PC1 | D15, PC1, ADC1, PCINT9 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| A2 | JANALOG · 11 | gpio | PC2 | D16, PC2, ADC2, PCINT10 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| A3 | JANALOG · 12 | gpio | PC3 | D17, PC3, ADC3, PCINT11 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| A4/SDA | JANALOG · 13 | gpio | PC4 | D18, PC4, ADC4, SDA, PCINT12 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| A5/SCL | JANALOG · 14 | gpio | PC5 | D19, PC5, ADC5, SCL, PCINT13 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D0 | JDIGITAL · 1 | gpio | PD0 | RX (Serial, to ATmega16U2), PD0, RXD, PCINT16 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D1 | JDIGITAL · 2 | gpio | PD1 | TX (Serial, to ATmega16U2), PD1, TXD, PCINT17 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D2 | JDIGITAL · 3 | gpio | PD2 | PD2, INT0, PCINT18 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D3 | JDIGITAL · 4 | gpio | PD3 | PWM (~D3), PD3, PCINT19, OC2B, INT1 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D4 | JDIGITAL · 5 | gpio | PD4 | PD4, PCINT20, XCK, T0 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D5 | JDIGITAL · 6 | gpio | PD5 | PWM (~D5), PD5, PCINT21, OC0B, T1 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D6 | JDIGITAL · 7 | gpio | PD6 | PWM (~D6), PD6, PCINT22, OC0A, AIN0 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D7 | JDIGITAL · 8 | gpio | PD7 | PD7, PCINT23, AIN1 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D8 | JDIGITAL · 9 | gpio | PB0 | PB0, PCINT0, CLKO, ICP1 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D9 | JDIGITAL · 10 | gpio | PB1 | PWM (~D9), PB1, PCINT1, OC1A | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D10/SS | JDIGITAL · 11 | gpio | PB2 | PWM (~D10), PB2, PCINT2, SS, OC1B | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D11/MOSI | JDIGITAL · 12 | gpio | PB3 | PWM (~D11), PB3, PCINT3, OC2A, MOSI | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D12/MISO | JDIGITAL · 13 | gpio | PB4 | PB4, PCINT4, MISO | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| D13/SCK | JDIGITAL · 14 | gpio | PB5 | LED_BUILTIN, PB5, SCK, PCINT5 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| GND | JDIGITAL · 15 | ground | — | ground | — | — | — | — | — | — | — |
| AREF | JDIGITAL · 16 | power in | AREF | power_in | — | — | — | — | — | — | — |
| SDA | JDIGITAL · 17 | gpio | PC4 | PC4, ADC4, SDA, PCINT12 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |
| SCL | JDIGITAL · 18 | gpio | PC5 | PC5, ADC5, SCL, PCINT13 | 3–5.5 V | -0.5–1.5 V | 4.2–5 V | ≤ 0.9 V | ≤ 40 mA | ≤ 40 mA | yes |

## Where to buy

| Supplier | Price | Stock | Checked | URL |
| --- | --- | --- | --- | --- |
| Arduino Store (USA) | 27.6 USD | in_stock | 2026-09-24 | https://store-usa.arduino.cc/products/arduino-uno-rev3 |

## FAQ

**What microcontroller does the Arduino UNO R3 use?**

The Arduino UNO R3 is built around the ATmega328P, alongside ATmega16U2, SPX1117M3-L-5, LMV358LIST-A.9, ECS-160-20-4X-DU.

**How many GPIO pins does the Arduino UNO R3 have?**

20 GPIO pins are exposed. Xirkit documents 32 board pins, 23 of them with pin-level electrical limits.

**Are the Arduino UNO R3 I/O pins 5 V tolerant?**

Yes, the documented I/O pins are 5 V tolerant. Input-high threshold: 3–5.5 V.

**How much current can a Arduino UNO R3 GPIO pin source?**

Documented output-high current per pin: ≤ 40 mA. Values are traced to the chip datasheet; see the pinout table for per-pin limits and conditions.

**What voltage powers the Arduino UNO R3?**

Supply range 1–20 V. Power inputs: VIN (6–20 V), AREF (1–5 V).

**How much does the Arduino UNO R3 cost?**

From $27.6 at Arduino Store (USA). Prices are observed unit prices before tax and shipping.

**What are the Arduino UNO R3 dimensions?**

68.58 × 53.34 mm. A STEP model is available for enclosure fit checks.

**Which interfaces does the Arduino UNO R3 support?**

gpio, control, interrupt, adc, i2c, uart, pwm, timer, analog_comparator, clock, spi, led, usb.

**How do I program the Arduino UNO R3?**

Supported frameworks: Arduino IDE, Arduino Cloud Editor.

**Where does this Arduino UNO R3 data come from?**

Every value in this record is traced to a source — 2 documents including the board and chip datasheets — with the page and table cited per value. Unknowns are left explicit, never guessed.

## Sources

- [Arduino UNO R3 datasheet](https://docs.arduino.cc/resources/datasheets/A000066-datasheet.pdf)
- [Arduino Store (USA) listing](https://store-usa.arduino.cc/products/arduino-uno-rev3)

## Part graph

### Built from

- [ATmega328P](https://www.xirkit.io/products/category/dev-boards/atmega328p) — main processor on the Arduino UNO R3
- ATmega16U2 — usb uart bridge on the Arduino UNO R3
- SPX1117M3-L-5 — voltage regulator on the Arduino UNO R3
- LMV358LIST-A.9 — op amp on the Arduino UNO R3
- ECS-160-20-4X-DU — resonator on the Arduino UNO R3

### Alternatives (by use case)

- [STM32 Nucleo-64 NUCLEO-F446RE (MB1136)](https://www.xirkit.io/products/stmicroelectronics-stm32-nucleo-64-nucleo-f446re-mb1136-2179) — Both serve arduino shield ecosystem — check the trade-offs; $18.66 vs $27.6
- [Arduino Mega 2560 Rev3](https://www.xirkit.io/products/arduino-mega-2560-rev3-e196) — Both serve 5 v sensors — check the trade-offs; $49.9 vs $27.6
- [Arduino Nano](https://www.xirkit.io/products/arduino-nano-b854) — Both serve 5 v sensors — check the trade-offs; $25.7 vs $27.6

### Newer generation

- [Arduino UNO R4 Minima](https://www.xirkit.io/products/arduino-uno-r4-minima-4540) — Arduino UNO R4 Minima is the newer generation of the Arduino UNO R3
- [Arduino UNO R4 WiFi](https://www.xirkit.io/products/arduino-uno-r4-wifi-d7ab) — Arduino UNO R4 WiFi is the newer generation of the Arduino UNO R3