# ESP32 vs Arduino Uno: which board for your project? > ESP32 or Arduino Uno? Logic level, speed, memory, Wi-Fi, ADC and pin current compared from the datasheets, with typical projects for each board. [HTML version](https://soldr.ai/blog/esp32-vs-arduino-uno) 8 November 2026 ยท Soldr **Short answer:** pick the **ESP32** if the project needs Wi-Fi or Bluetooth, a colour screen, or more memory and speed. Pick the **Arduino Uno** if it's a simple 5 V project with 5 V sensors or shields, or if you want the simplest wiring rules. The biggest practical difference isn't speed: it's that the ESP32 runs at 3.3 V and the Uno at 5 V. The ESP32 and the Uno are the two boards most people start with, and they're not really rivals. They suit different projects. Every number below comes from the manufacturer's datasheet or official page, via our reference pages for the [ESP32](https://soldr.ai/docs/boards/esp32-30-pin), the [ESP32-WROOM-32 module](https://soldr.ai/docs/boards/esp32-wroom-32), the [Arduino UNO R3](https://soldr.ai/docs/boards/arduino-uno-r3-a000066) and its [ATmega328P chip](https://soldr.ai/docs/boards/atmega328p-pu). ## Side by side - **Logic level:** ESP32 3.3 V (the chip's supply is 3.0 to 3.6 V). Uno 5 V. - **Processor:** ESP32 dual-core at up to 240 MHz. Uno: ATmega328P at 16 MHz. - **Memory:** ESP32-WROOM-32: 520 KB SRAM and 4 MB flash. Uno: 2 KB SRAM and 32 KB flash. - **Wireless:** ESP32: 2.4 GHz Wi-Fi (802.11 b/g/n) and Bluetooth 4.2 with BLE. Uno: none. - **Analog inputs:** ESP32: 12-bit ADC, up to 18 channels on the chip. Uno: 6 channels, 10-bit. - **Pin current:** Uno: 20 mA maximum per I/O pin. ESP32: about 40 mA source and 28 mA sink typical at maximum drive strength; design well under both. - **Supply:** the ESP32 module wants a supply that can deliver at least 0.5 A, because Wi-Fi transmit bursts reach about 240 mA. The Uno runs happily from USB for small projects. ## When the Uno is the better choice - **5 V parts.** Many hobby modules and shields are built for 5 V. On a Uno they connect directly. On an ESP32 some of them need a level shifter or a voltage divider (more in [5 V sensors on a 3.3 V ESP32](https://soldr.ai/blog/5v-sensor-3v3-esp32-logic-levels)). - **Shields.** The Uno's header is the format most shields are made for, such as a [CNC shield](https://soldr.ai/docs/components/cnc-shield-v3) or a motor shield. - **Simple pin rules.** Apart from D0 and D1 (the serial port), the Uno's pins are general purpose. The ESP32 has pins that set the boot mode at reset (GPIO0, GPIO2, GPIO12, GPIO15), pins wired to the module's flash (GPIO6 to GPIO11) and six input-only pins. None of that is hard, but it's more to know. - **Learning.** Fewer moving parts makes the first project easier to debug. ## When the ESP32 is the better choice - **Anything connected.** A web dashboard, phone control over Bluetooth, sending readings to a server: the ESP32 has the radio built in. - **Screens and animation.** A colour TFT needs memory for the image and speed to redraw it. 520 KB of SRAM against 2 KB is the difference between smooth and impossible. - **More inputs, finer readings.** More analog channels at 12 bits instead of 10. - **3.3 V sensors.** Many newer sensor and display chips are 3.3 V parts: the BME280 is rated 1.71 to 3.6 V, and the SSD1306 OLED controller's logic supply 1.65 to 3.3 V. On an ESP32 they match without any level shifting. ## The 3.3 V rule that catches people The ESP32's datasheet gives the input-high limit as VDD + 0.3 V, which is 3.6 V on a 3.3 V supply. A 5 V signal on an ESP32 input pin is outside that rating. If a sensor outputs 5 V, such as the echo pin of an HC-SR04 ultrasonic sensor, it needs a divider or a level shifter before it reaches the ESP32. Going the other way, a 3.3 V output driving a 5 V input often works, but only if the input's datasheet says 3.3 V counts as high. ## A few typical projects - **Parking sensor with a buzzer:** Uno. 5 V ultrasonic sensor, simple logic, no network. - **Weather station that shows readings on your phone:** ESP32. Wi-Fi, and the common sensors are 3.3 V. - **Desk toy with a motion sensor and a small OLED:** either. Both parts are I2C. The ESP32 gives you room for animation. - **Touch-screen game with sound:** ESP32, for the memory and the speed. ## What about the Uno R4 and the Nano? Two boards sit between these two: - **The [Arduino UNO R4 WiFi](https://soldr.ai/docs/boards/uno-r4-wifi)** keeps the Uno shape and 5 V I/O but moves to a Renesas RA4M1 at 48 MHz with 256 kB of flash and 32 kB of SRAM, and adds an ESP32-S3 module for Wi-Fi and Bluetooth. Its datasheet gives a lower limit per pin than the classic Uno: 8 mA per GPIO. The [UNO R4 Minima](https://soldr.ai/docs/boards/uno-r4-minima) is the same main chip without the radio. - **The [Arduino Nano](https://soldr.ai/docs/boards/arduino-nano-a000005)** is the classic Uno's chip in a breadboard format: same ATmega328P family, same 5 V logic, 8 analog inputs instead of 6. If you like the Uno's 5 V simplicity but need Wi-Fi, the R4 WiFi is the middle path. If you need the ESP32's memory and pin count, go straight to the ESP32. ## Not sure? Let the build decide When you describe a project on Soldr without naming a board, it asks which platform you want before it picks any parts, and says what each is best for. You can answer "ESP32" or "Uno", or say "you pick" and it chooses and explains why. Whichever you choose, the build checks the parts against that board's logic level and power, and the code is compiled for that exact board before you see it. Both boards are on Compoden: the [ESP32-DevKitC](https://compoden.com/products/esp32-devkitc-development-board-black-wifi-bluetooth-module), the [original Arduino UNO R3](https://compoden.com/products/arduino-uno-r3-original-atmega328p-microcontroller-board) and a [compatible Uno R3](https://compoden.com/products/uno-r3-ch340g-atmega328p-board-arduino-compatible). What's the difference between those last two? See [original vs compatible Arduino boards](https://soldr.ai/blog/original-vs-compatible-arduino-uno-nano). Describe your project on [app.soldr.ai](https://app.soldr.ai). Sign in and get 100 credits free.