Boards compared

Ten differences between Raspberry Pi and Arduino

By Bulan Sarkar, founder of ElectronicsInfoline (since 2000) · About a 10-minute read

A Raspberry Pi is a small computer that runs Linux. An Arduino UNO is a microcontroller board that runs one program you wrote, and nothing else. Both have pins you can wire things to, which is why people compare them, but they solve different problems.

Here are ten differences that decide which one a project needs, using the boards you can buy now: the Raspberry Pi 5 and the UNO R3 and R4 Minima. Every number comes from the makers' own documents, listed at the end.

Pick a Raspberry Pi when the project needs an operating system: a screen, a camera, a network service, files or Python libraries. Pick an Arduino when it needs to read sensors and switch things reliably, start the moment power arrives, survive being unplugged, or run for months on a battery.

The numbers are far apart: the smallest Pi 5 has 524,288 times the UNO R3's 2 kB of RAM and draws about 4.00 W, while the UNO's chip runs on 26 mW. Many projects use both, with the Pi running the software and the network and the Arduino reading sensors and driving outputs.

The gap in numbers

Clock, Pi 5 core against UNO R3: 150×
20 Wh battery, Pi 5 running: 5.0 h
20 Wh battery, UNO chip running: 32 days
UNO R4 pin limit: 8 mA

The ten differences at a glance

Figure 1. Ten differences between a Raspberry Pi 5 and an Arduino UNO (R3 and R4 Minima), one line each. Each one has its own section below.

1. A computer against a controller

The Pi 5 is built like a PC: a processor, separate RAM, an I/O chip, and an operating system loaded from a microSD card. Your program is one of many processes Linux runs, and you can write it in Python, C, JavaScript or anything else that runs on Linux.

The UNO is one chip, the ATmega328P on the R3 and the Renesas RA4M1 on the R4, with the processor, program memory, RAM and analogue converter inside it (Arduino). You write a sketch in C++, upload it over USB, and from then on the chip runs that sketch and nothing else, from the moment power arrives.

Figure 2. Inside each board. The Pi spreads the work over several chips and an operating system; the UNO puts everything on one microcontroller.

2. Clock speed

The Pi 5's BCM2712 runs four Arm Cortex-A76 cores at 2.4 GHz (Raspberry Pi Ltd). The UNO R3 runs at 16 MHz, and the R4 Minima at 48 MHz (Arduino). One Pi core ticks 150 times as fast as the R3, and the Pi has four of them, each doing more per tick.

Figure 3. Clock frequency on a log scale: 2.4 GHz for one Pi 5 core, 48 MHz for the UNO R4, 16 MHz for the UNO R3.

Our take: speed rarely decides this choice. 16 MHz is plenty to read a sensor, drive a display or run a motor controller. Speed matters when the job is image processing, a web server or a lot of maths on floating-point numbers.

3. Memory

The Pi 5 comes with 1, 2, 4, 8 or 16 GB of RAM (Raspberry Pi Ltd). The UNO R3 has 2 kB of SRAM and 32 kB of flash for the program; the R4 Minima has 32 kB and 256 kB (Arduino). Even the smallest Pi 5 has 524,288 times the R3's RAM.

Figure 4. RAM on a log scale. The smallest Pi 5 (1 GB) against 32 kB on the UNO R4 and 2 kB on the UNO R3.

On an R3, 2 kB is about 2,000 characters of text. A sketch that builds long strings or buffers a few hundred sensor readings runs out, usually by crashing or resetting rather than with an error message. On a Pi, memory is something you stop thinking about for most projects.

4. Storage, booting and pulling the plug

The Pi boots Linux from a microSD card (or a USB or NVMe drive), which takes time, and it should be shut down before the power goes. Cut the power while it is writing and the card's file system can be damaged, and then it won't boot. The Pi 5 adds a power button for a clean shutdown (Raspberry Pi Ltd).

The UNO keeps its sketch in flash inside the chip and only reads it. Cut the power whenever you like; when it comes back, the sketch simply starts again from the top. For a gadget that someone switches off at the wall, that alone can decide the choice.

5. Power, and how long a battery lasts

Raspberry Pi gives the Pi 5's typical bare-board current as 800 mA and asks for a 5 V, 5 A supply (25 W). On a weaker supply it limits the USB ports to 600 mA in total instead of 1.6 A (Raspberry Pi documentation). The Raspberry Pi Zero 2 W needs 350 mA.

The UNO R3's own data sheet leaves its power line blank (it prints "xx mA") (Arduino), so the figures we can source are for its chip. The ATmega328P draws 5.2 mA at 5 V running at 8 MHz, and 4.199999999999999 µA at 3 V in power-down sleep with the watchdog awake to wake it (Microchip). A whole UNO board draws more than its chip: the USB interface chip, the regulator and the power LED all take current.

Figure 5. How long a 20 Wh battery lasts at each power draw, log scale, ignoring converter losses. A sleeping ATmega328P outlasts the battery's own shelf life.

A 20 Wh pack, roughly what a 5,000 mAh phone power bank holds, runs a Pi 5 for 5.0 h and a Zero 2 W for 11.4 h. The same pack runs a bare ATmega328P for 32 days awake, and asleep it would last 181 years on paper, which means the battery goes flat on its own first. That is why battery sensors are built around a microcontroller that sleeps between readings, not a Linux board.

6. Logic voltage: 3.3 V against 5 V

Every Pi GPIO pin works at 3.3 V. Outputs go to 3.3 V, and inputs are rated for 3.3 V only (Raspberry Pi documentation). Connect a 5 V signal to a Pi pin and you can damage the chip. The UNO R3 and R4 Minima run their pins at 5 V.

Going the other way, from Pi to UNO, the problem is smaller but still there. An ATmega328P input is guaranteed to read HIGH only above 3.0 V at 5 V (Microchip). Raspberry Pi guarantees its output only down to 2.6 V (Pi 4 table, at 4 mA) (Raspberry Pi documentation). That is 0.4 V short. It usually works on the bench, because a lightly loaded pin sits near 3.3 V, but it isn't guaranteed. A 74AHCT125 buffer reads HIGH from 2.0 V (Texas Instruments), which leaves 0.6 V to spare.

Figure 6. The voltage each input needs to read HIGH, against the Pi's guaranteed output of 2.6 V (dashed line). The UNO R3 pin needs more than the Pi guarantees; a 74AHCT125 needs less.

A common job is a serial link: the Pi sends commands, the UNO answers. The UNO's TX line goes through a 2.2 kΩ / 3.3 kΩ divider, which turns 5 V into 3.00 V and a 5.25 V rail into 3.15 V, still under the Pi's 3.3 V. The UNO's weakest guaranteed HIGH, 4.2 V, still lands at 2.52 V, above the Pi's 2.0 V threshold. The Pi's TX goes through the buffer.

Figure 7. A Pi-to-UNO serial link. UNO TX through 2.2 kΩ and 3.3 kΩ gives 3.00 V at the Pi; the Pi's TX reaches the UNO through a 74AHCT125 powered from 5 V.

Is the divider fast enough? Its 1.32 kΩ source resistance into about 12 pF of pin and wire gives a rise time of 35 ns. At 115,200 baud a bit lasts 8.68 µs, so the edge takes 0.4 % of a bit. It draws 0.91 mA while the line is high. Our level shifter guide covers the other ways to do it, including I²C.

7. Analogue inputs

The UNO has six analogue inputs, A0 to A5. On the R3 the converter is 10-bit, so with the default 5 V reference one step is 4.88 mV. The R4 Minima reads up to 14 bits (Arduino), a step of 0.305 mV, once you call analogReadResolution(14); by default it returns 10 bits like the R3.

The Pi has no analogue inputs at all. A potentiometer, a light-dependent resistor or an analogue temperature sensor needs an external converter chip on SPI or I²C, or an Arduino reading it and sending the number to the Pi.

Figure 8. The smallest voltage change each UNO can see on a 5 V reference: 4.88 mV at 10 bits, 0.305 mV at 14 bits. The Pi has no analogue input to compare.

The ADC lesson explains where the step comes from.

8. How much current a pin can give

The ATmega328P on an R3 has an absolute maximum of 40 mA per pin (Microchip), and its data sheet quotes output voltages at 20 mA, which is the usual working limit. The R4 Minima is different: Arduino says its pins handle up to 8 mA (Arduino). On the Pi, all GPIO pins together should stay under 50 mA (Raspberry Pi documentation).

That catches people moving an old sketch to an R4. The 220 Ω resistor from many beginner tutorials, with a red LED of about 2.0 V, lets 13.6 mA flow from a 5 V pin. Fine on an R3, over the limit on an R4. The R4 needs at least 375 Ω, so 390 Ω, which gives 7.7 mA.

Figure 9. LED current from one pin, red LED at 2.0 V. Red: over that board's limit. The classic 220 Ω is too small for the UNO R4.

Neither board should drive a motor, relay coil or LED strip from a pin. Use a transistor or MOSFET; our MOSFET guide shows which ones switch fully from 3.3 V and 5 V, and the LED resistor calculator works out the resistor for any LED and supply.

9. Timing you can count on

On an UNO, your sketch is the only thing running, so a loop that pulses a pin every 100 µs does it every time. The micros() timer counts in 4 µs steps on a 16 MHz board (Arduino language reference).

On a Pi, Linux decides when your program runs. Most of the time it runs at once, but a disk write, a network burst or another process can hold it up for a while, and you can't say in advance how long. That is fine for a weather logger that reads once a minute. It is not fine for decoding an IR remote, driving WS2812 LEDs from plain code or stepping a motor smoothly. Those jobs go to a microcontroller, or to the Pi's hardware peripherals through a driver.

10. Connections and peripherals

The Pi 5 has dual-band Wi-Fi, Bluetooth 5.0, Gigabit Ethernet, two USB 3.0 and two USB 2.0 ports, two 4K HDMI outputs, two camera or display connectors and a PCIe lane that takes an SSD through an adapter (Raspberry Pi Ltd). A camera, a screen and a keyboard plug straight in.

The UNO R3 and R4 Minima have one USB port, used to upload sketches and to talk serial to a computer. Wi-Fi needs another board: the UNO R4 WiFi, an ESP32, or a shield. Raspberry Pi says the Pi 5 stays in production until at least January 2036 (Raspberry Pi Ltd), which matters if you design it into a product.

Which one to choose

Figure 10. Work down the questions; the first yes decides. Projects that answer yes to both a top and a bottom question use a Pi and an Arduino together, joined as in figure 7.

What we'd do: start a first electronics project on an UNO, because one chip and one program are easier to reason about. Add a Pi when the project needs a screen, a camera or the network, and let the UNO keep the sensors and the timing.

Tips and checks

Before you wire a sensor module to a Pi, check what voltage its output swings to. Many breakout boards run at 5 V.
Shut a Pi down with the power button or sudo shutdown now, then wait for the activity LED to stop before you cut the power.
Use the 5 A supply on a Pi 5 if anything is plugged into its USB ports; on a 3 A supply they share 600 mA.
Moving an R3 project to an R4 Minima? Check every pin that drives an LED or a transistor base against the 8 mA limit.
For a Pi and an UNO on one bench, join their grounds before anything else.

Questions people ask

Is a Raspberry Pi better than an Arduino?

Neither is better; they do different jobs. A Pi is a Linux computer for screens, cameras and network software. An Arduino is a microcontroller for sensors, motors and timing, and it can run for weeks on a battery.

Can I connect an Arduino to a Raspberry Pi?

Yes. The simplest way is a USB cable, which gives the Pi a serial port to the UNO. To use the pins instead, put a 2.2 kΩ / 3.3 kΩ divider on the UNO's TX line and a 74AHCT125 on the Pi's TX line, and join the grounds.

Can a Raspberry Pi read analogue sensors?

Not directly. It has no analogue inputs, so it needs an external ADC chip on SPI or I²C, or an Arduino that reads the sensor and sends the value.

Which is better for a beginner?

An Arduino UNO for learning electronics, because the code and the circuit are the whole system. A Raspberry Pi for learning programming and Linux, or when the project needs a screen or the internet.

Lessons behind the numbers

Sources and assumptions

Raspberry Pi Ltd, Raspberry Pi 5 Product Brief (October 2026), Specification, p. 2 (BCM2712, 2.4 GHz quad-core 64-bit Arm Cortex-A76; LPDDR4X in 1, 2, 4, 8 and 16 GB; dual-band 802.11ac Wi-Fi, Bluetooth 5.0, Gigabit Ethernet, 2 × USB 3.0, 2 × USB 2.0, dual 4Kp60 HDMI; 5 V / 5 A over USB-C; RTC, power button; in production until at least January 2036)
Raspberry Pi documentation, Raspberry Pi hardware: Power supply, Typical power requirements (Pi 5: 5.0 A recommended supply, 1.6 A for USB peripherals (600 mA on a 3 A supply), 800 mA typical bare-board active current; Zero 2 W: 350 mA; GPIO pins combined 50 mA maximum)
Raspberry Pi documentation, Raspberry Pi hardware: GPIO, voltage specifications for BCM2711 (4-series) (GPIO outputs 3.3 V, inputs 3.3 V-tolerant; VIH min 2.0 V, VIL max 0.8 V; VOH min 2.6 V at 4 mA (default drive 4 mA, maximum 8 mA); no table published for Raspberry Pi 5)
Arduino, UNO R3 product reference manual, SKU A000066 (modified 14 October 2026), Features and 2.2 Power Consumption (ATmega328P, AVR CPU up to 16 MHz, 32 kB flash, 2 kB SRAM, 1 kB EEPROM; maximum power consumption printed as "xx mA" (no figure given))
Arduino, UNO R4 Minima product reference manual, SKU ABX00080 (modified 14 October 2026), Features and 9.3 Pin Current (Renesas RA4M1 (R7FA4M1AB3CFM#AA0), 48 MHz Arm Cortex-M4 with FPU, 5 V operating voltage, 256 kB flash, 32 kB SRAM, up to 14-bit ADC, 12-bit DAC; GPIOs handle up to 8 mA)
Microchip, ATmega48A/PA/88A/PA/168A/PA/328/P data sheet, DS40002061B (2020), §29.1 p. 308, Table 29-8 p. 312 and Table 30-1 p. 322 (DC current per I/O pin 40.0 mA absolute maximum; ATmega328P active 8 MHz at 5 V 5.2 mA typical (9 mA max); power-down with watchdog at 3 V 4.2 µA typical; Table 30-1, p. 322: output voltages specified at 20 mA)
Microchip, ATmega48A/PA/88A/PA/168A/PA/328/P data sheet, DS40002061B (2020), Table 30-1 Common DC characteristics, pp. 322–323 (VIH min 0.6 × VCC (VCC 2.4 to 5.5 V); VOH min 4.2 V at −20 mA, VCC 5 V)
Texas Instruments, SN74AHCT125 data sheet, SCLS264R, revised February 2024, §5.2 and §5.4 (VCC 4.5 to 5.5 V; VIH min 2 V, VIL max 0.8 V; IOH −8 mA; VOH min 3.8 V at −8 mA and 4.5 V)
Arduino language reference, millis() and micros() (millis() overflows after about 50 days; micros() has 4 µs resolution on 16 MHz boards)

Read on 15 October 2026. Raspberry Pi publishes a GPIO voltage table for the Pi 4 but none for the Pi 5's RP1 chip, so the logic-level figures use the Pi 4 table. The ATmega328P currents are for the chip alone at 8 MHz (the data sheet's nearest row to the UNO's 16 MHz), not the whole board. Our own choices: a 20 Wh battery with no converter losses, a red LED at 2.0 V, the 220 Ω starting resistor, the 2.2 kΩ / 3.3 kΩ divider, a 5 V rail of 4.75 to 5.25 V, 12 pF of pin and wire capacitance and 115,200 baud. This page rebuilds an older ElectronicsInfoline article of the same title; none of its text is reused.