The Lazy Comparison Guide: Arduino Leonardo vs UNO

Believe it or not, some people don’t enjoy making new things with Arduino boards. I used to hate it too, because I lacked confidence.

It requires coding and skills. Once you apply the right techniques and get a little confidence in using these microcontroller boards. You will get better with time and enjoy playing with electronic toys.

The Arduino boards come in various shapes and sizes with different functionality and features. Just like Arduino Lillypad is specially designed for e-textile and It requires coding and skills. Once you apply the right techniques and get a little confidence in using these microcontroller boards. You will get better with time and enjoy playing with the electronic toys wearable. Arduino UNO and Leonardo both work in the same way, but there are a few reasons Arduino has made it separately:

A crucial difference is that a UNO has a replaceable microcontroller (Atmega328) which gives an additional advantage to the user. So you don’t have to buy the whole board again. In contrast, Arduino Leonardo has a microcontroller (Atmega32u4) mounted on its surface which has built-in support for USB.

Every other Arduino board is unique in its own way and has its own features and benefits. Are you still confused and don’t understand which one to buy Arduino Leonardo or UNO?

Let’s have a quick look at the difference between Arduino UNO and Arduino Leonardo. Also, we will discuss things later by the end of this blog:

difference between Arduino Uno and Arduino Leonardo

Let’s dive into the differences between LEO and UNO. So you don’t get trouble trying new things.

What are the differences between Arduino Leonardo and UNO?

There are many types of Arduino boards available in the market, and most of you spend a lot of time and research on the internet to buy the right type of board.

I recommend you to not go into so many technical details at first. You can just simply start your Arduino journey from the Arduino UNO or Leonardo. They both are the simplest and easiest among the Arduino family. It has everything which you need to get started.

Both Arduino UNO and Leonardo are official Arduino boards, and it also works on the same software (Arduino IDE). Arduino software is free to use and you can download it from Arduino. cc website.

Before you waste your time on different types of microcontroller boards; here are the differences between Arduino UNO and Leonardo which may help you in decision-making.

Arduino Leonardo Vs UNO

Here is a quick tip: Don’t buy any second-hand Arduino boards.

There are pretty obvious differences that can be seen with our naked eyes.

    • Microcontroller–They both use the same series microcontroller but LEO uses a surface-mounted Atmega32U4 which has support for USB. At the same time, UNO uses a replaceable microcontroller Atmega328p which can be restored when you somehow burn its driver or microcontroller. You don’t need to buy the whole board again. You can re-use it after replacing the microcontroller.
    • FTDI chip – There is no FTDI chip in UNO which is used to translate a USB signal into a serial communication. Microcontroller Atmega32U4 has serial ports and a native USB.
    • USB B-class connector–They have also replaced the USB b-class connector with a micro USB connection.
    • Paint job–Leonardo has smooth and dark paint so you can see clearly what has been written on the board or the pin numbers.
    • Input/Output pins–Leonardo has more pins than UNO. Leonardo has 23 pins and each pin can be used as input or output. You can easily connect other compatible devices like drivers, and sensors with the board and make your innovation into reality.
    • Price–Leonardo is 20% cheaper than the UNO board.
    • USB support–It gives an additional facility of USB in Arduino Leonardo board for the students and hobbyists who want to create more projects with USB.


Arduino UNO Arduino Leonardo


Atmega328 Atmega32u4

Operating voltage

5V 5V

Recommended Input voltage

7-12V 7-12V

Digital I/O pins

14 20

PWM pins

6 7

Analog input channels

6 12

Flash Memory

32Kb (0.5 Kb used by bootloader) 32Kb (4 kb used by bootloader)

Clock Speed

16Mhz 16 Mhz


1024 bytes 1Kb


2 Kb 2.5 Kb


68.6mm 68.6 mm


53.3mm 53.3 mm


20 gm 20 gm

DC current for 3.3V Pin

50 mA 50 mA

DC current (Input/output pin)

20 mA 40 mA

Pin Descriptions of Arduino UNO and Leonardo

Power Pins

You have now understood the most obvious difference between these boards. Now let’s dive into the power pin which could give you an advantage.

Power pins play an essential role in Arduino which power up the Arduino, sensors, motor drivers, and shields. Power pins are pretty much the same in each type of Arduino board.

There are two ways to power up the Arduino boards:

  • AC-DC adaptor, from an external source supply that is the battery.
  • You can also power up your Arduino with your laptop with the help of a Printer Cable.
power pins of arduino Mega

VINVIN pin uses to power another Arduino, and can also be used to power other sensors and drivers. If you supply an external power source i-e a battery or power supply. GND and VIN can also start your board, but I would suggest that you use a battery (preferably a 9 to 12V battery) because of the voltage dropout. The maker of this board has already fixed a built-in regulator so it would only allow fixed 5V to the Arduino.

Tip: You can use this pin to power other components, such as motor drivers, shields, Arduino, and sensors only if you supply power through a barrel jack or from a USB cable.

5VMost of the time 5V pin is used to power up the drivers and shields like RFID, sensors, and Bluetooth (a 5V pin is limited to 500 mA current if you are using an Arduino with a USB cable).

The onboard voltage regulator is limited to 800 mA but because of some power issues, you shouldn’t exceed more than 500 mA. It might damage your board.

3.3VRegulated output, can be used to power up components that run at 3.3V.

GNDGround pin

Digital input and output pins can be used in both ways either input or output using pinmode(), digitalread(), digitalwrite() functions. Each of the pins operate at 5v, and provides or receives the maximum amount of 40 mA current.


Digital Pins

Some pins are designed to perform specialized functions:

0(RX) and 1(TX) – are used for receiving the data and transmitting data respectively.

SDA and SCL – SDA and SCL stand for serial data and serial clock respectively. They both support two-wire interface (TWI) communication using the wire library. Two wire interfaces TWI and I2C are quite similar.

PWM–3, 5, 6, 9, 10, 11, and 13 analogWrite() function is used to provide 8-bit PWM output.

LED 13 – built-in LED is fixed at pin number 13.

Arduino is pretty famous among students, teachers, and hobbyists because of its affordable price, and easy to use of hardware and software, but Arduino UNO gained much popularity among all the Arduino boards. Here are a few points why UNO is popular:

  • Arduino UNO is famous because of its simple architecture and its pinout structure is quite easy to understand.
  • Most of the UNO shields don’t support Leonardo. On comparison, Arduino UNO is compatible with almost every driver and shield.
  • Tutorials of UNO are easily available on cyberspace while some of the uno code doesn’t support Leonardo.

So far, you have understood the difference between these two boards and it would help you to select the right one, but there are a few cool features that make Arduino Leonardo unique:

  • Arduino Leonardo supports a microcontroller (Atmega32u4) which has built-in support for USB. It also has a USB communication port which helps you to directly run your sketches. Since Leo doesn’t require an additional microcontroller for communication, but UNO requires one.
  • Arduino Leonardo has more digital and input-output pins.

Arduino is an ongoing learning process, and you get better by the time when you start practicing daily. Here are a few more articles on Arduino which might help you in gaining more knowledge about Arduino and its family.

How to select which Arduino board is better? Difference between Arduino UNO and Arduino Leonardo?

Attributes Leonardo UNO
Microcontroller The microcontroller used in Leo is ATmega32u4. The microcontroller used in UNO is ATmega328.
I/O Pins 23 digital pins are used in the circuit. The ICSP header has three digital pins that are not repeated. The digital pins used in the circuit are 20. The ICSP header has three digital pins which are repeated.
Channels of pulse width modulation There are seven channels. There are six PWM channels.
Input pin for analog signals Total of twelve pins are allocated as analog input pins. There are six pins allocated as analog input pins.
SRAM The 2.5KB is used in SRAM. 2KB of memory is allotted in SRAM.
Clock speed The clock speed is 16MHZ resonator. The clock speed is 16MHZ crystal.
Operating voltage The advisable operating voltage ranges from 7V to 12V. The advisable operating voltage ranges from 7V to 12V.
USB connector The USB connector is type B. The USB connector is type Micro-B.
Weightage The weight of the circuit is 28g. The weight of the circuit is 20g.

According to necessity, the usage of Arduino Leonardo and UNO is chosen within the circuits. It offers a clear and simple programming environment. The hardware component of the microcontroller can be effortlessly modified which is utilized to plan, create, and test numerous complex electronic circuits and prototypes.

What languages do Arduino Leonardo and Arduino UNO use?

The Arduino Integrated Development Environment (IDE) could be a cross-platform application (for Windows, macOS, Linux) that’s composed in capacities from C and C++. It is utilized to type in and upload programs to Arduino consistent boards, but too, with the assistance of third-party centers, and other seller advancement boards.

The Arduino IDE underpins the dialects C and C++ utilizing extraordinary rules of code structuring. The Arduino programming language supplies a program library from the wiring project, which gives numerous common input and output procedures. User-written code as it were requires two fundamental capacities, for beginning the portray and the most program circle, that is compiled and connected with a program stub fundamental() into an executable cyclic official program with the GNU toolchain.

What makes them unique?

Popularity and User-Friendly

The tutorials and information to learn Arduino Leonardo or UNO are widespread. But when compared to Arduino Leonardo, the UNO has a huge community with a firm back and the lessons of UNO are effortlessly open in cyberspace whereas Arduino Leonardo isn’t easily gotten to as UNO as it isn’t compatible and user-friendly. The board of UNO includes a modifying combine based on the USB port and it avoids the circuit from over-voltage.

Easily available

UNO is popular for its numerous defending shields which made it super fit within the board. Here the shields are created to become more consistent and feasible. The numerous Arduino shields will cause issues with Arduino Leonardo. All of the UNO shields are not compact and work with Arduino Leonardo which may be a common voice raised in the Arduino committee.

UNO community

The ever-growing Arduino community is made up of everybody from hobbyists and students to creators and engineers all over the world. Have questions? The official multi-language Gathering is the put-to-go. Check out the Play area for a collection of Arduino information, instructional exercises, and tips provided by your individual Arduino clients. For data on the advancement of Arduino, see the Arduino extension on GitHub.

Which board is more popular?

Whereas there are numerous assortments of Arduino boards on the showcase, there is a modest bunch that is most commonly seen. The foremost commonly utilized Arduino board by both engineers and specialists include:

Arduino UNO

The UNO is apparently the foremost well-known Arduino. It is powered by an Atmega328 processor working at 16MHz, incorporates 32KB of program memory, 1KB of EEPROM, 2 KB of Slam, and has 14 advanced I/O, 6 analog inputs, and both 5V and 3.3V control rails.

The Arduino UNO contains a stick header course of action that’s quickly getting to be the industry standard for advancement boards, making it congruous with most advancement board shields on the market.

Although the UNO is the foremost prevalent board, all boards have great support through online forums, thanks to the common engineering and the utilization of a common language and IDE. This implies that you just are unlikely to drop into device-specific traps that might anticipate a chunk of code from working since of equipment setups or inherent bugs.
Arduino UNO board description

Arduino code can be effectively transferred to a distinctive board with essentially no changes which is exceedingly advantageous to any architect needing to alter their intellect almost to what board their extent will utilize.

The cost difference between Arduino UNO and Leonardo

Leonardo is 20% cheaper than the UNO board. USB bolster – It gives an extra office of USB in Arduino Leonardo board for the students.

The price of Arduino UNO is $22.50 and the price of Leonardo is $7.88. You can get Arduino UNO from this link. For getting Leonardo just go there.

Mataf Khan

An electronics enthusiasts from childhood became an electrical engineer, I've been playing with Arduino and other electronics gadgets like raspberry pi since when I was 14. and have a passion of troubleshooting Arduino problems.

Recent Posts