Arduino UNO and MEGA Differences

Posted: July 21, 2025
Last Updated: July 3, 2025

Planning on taking larger or more complicated tasks for your Arduino projects? Upgrade your UNO to the MEGA to satisfy your needs. Learn about Arduino UNO and MEGA differences here.

INtroduction

You may find the Arduino UNO limiting for some of your projects. Firstly, it has limited I/O pins (14 digital I/O pins (6 PWM) and 6 analog inputs). Second, the UNO has limited memory (32KB of flash memory, 2KB of SRAM, and 1KB of EEPROM). Finally, the UNO is not meant for more comlpex and larger projects. With this you’ll need a much beefier Arduino development board.

However, you’d still want compatibility with your Arduino shields and the vast resources of information of the Arduino library. The Arduino MEGA 2560 is the perfect choice for an upgrade.

Arduino UNO vs. Arduino MEGA

MAjor Differences

Below, you can see the major differences between the two development boards. Certainly, the Arduino MEGA has more of everything, including I/O pins, memory, and even UART serial ports. This allows you to use the MEGA for larger and more complex projects.

Basic Feature	Arduino UNO	Arduino MEGA
Microcontroller	ATmega328P	ATmega2560
Digital I/O Pins	14 (6 PWM)	54 (15 PWM)
UART Serial Ports	1	4
Analog Input Pins	6	16
Flash Memory	32KB	256KB
SRAM	2KB	8KB
EEPROM	1KB	4KB
Clock Speed	16MHz	16MHz

About Using Arduino Shields

Arduino Shields are at the heart of compatibility for various hardware for the UNO and MEGA. The good news is that, based on the layout of the header pins, the Arduino shield header pins should fit both the UNO and MEGA. However, note that because of the differences between the UNO and the MEGA, some pins are not the same. With this, you’ll have to be aware of this or make some adjustments in the code. Below are some of their differences.

Pins	UNO	MEGA
I2C (SDA/SCL)	Pins A4 (SDA) and A5 (SCL)	Pins 20 (SDA) and 21 (SCL)
SPI (MISO/MOSI/SCK)	Pins 12 (MISO), 11 (MOSI), 13 (SCK)	Pins 50 (MISO), 51 (MOSI), 52 (SCK)

Note that the SPI pins are shared with the programming ICSP lines of both the UNO and MEGA. Usually, you’ll see them both in the same location on the development boards.

Conclusion

To wrap it all up, the Arduino MEGA is a much more powerful dev board, with more memory (Flash, SRAM, and EEPROM), I/O pins, UART ports, and ADC channels than its counterpart, the Arduino UNO. Interestingly, you may be able to use the same Arduino shield for both the UNO and MEGA, as long as you check specific ports/pins that you can adjust.