Arduino memory management is critical for reliable embedded systems. Running out of SRAM causes silent crashes, stack corruption, and random resets. This guide covers Flash, SRAM, and EEPROM specs for every major Arduino board plus proven optimization strategies.
| Board | MCU | Flash | SRAM | EEPROM | Arch | Clock |
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Memory Optimization Techniques
How to Use the Arduino Memory Guide
This Arduino memory guide lists SRAM, Flash, and EEPROM specifications for every major Arduino board. Use the search to find your board. The optimization tips below apply universally to memory-constrained sketches.
Monitoring Memory Usage
The Arduino IDE shows Flash usage after compilation. To check available SRAM at runtime, use: Serial.println(freeMemory()) with the MemoryFree library. If free SRAM drops below 100 bytes, you're at risk of crashes. The typical stack frame is 10-50 bytes per function call.
The F() Macro is Essential
Every string literal in your code gets copied to SRAM by default. Serial.println("Hello World") uses 12 bytes of SRAM. With F(): Serial.println(F("Hello World")) uses zero SRAM. On a 2KB Uno, this is critical — a dozen strings can consume 20% of your SRAM.
Choosing the Right Board
For data logging or network projects: Arduino Mega (8KB SRAM) or Arduino Due (96KB SRAM). For IoT: ESP32-based Arduino (520KB SRAM). For battery-powered sensors: Arduino Nano Every (6KB SRAM, lower power). The Arduino Uno (2KB) is excellent for learning but becomes limiting once you add LCD, SD card, and WiFi simultaneously.
FAQ
Is this Arduino memory guide free?
Yes, completely free. Reference memory specs for any Arduino board without any account or payment.
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What is the difference between SRAM, Flash, and EEPROM on Arduino?
Flash stores the program code (read-only at runtime). SRAM is working memory for variables, stack, and heap (volatile, cleared on reset). EEPROM is non-volatile data storage that persists across reboots, used for settings and calibration data. SRAM is the most limited resource.
How much SRAM does an Arduino Uno have?
The Arduino Uno (ATmega328P) has 2KB of SRAM. This shared space holds global variables, local variables, the stack, and the heap. Running out of SRAM causes silent resets or undefined behavior — a very common source of Arduino bugs.
What is the F() macro and how does it save memory?
F() keeps string literals in Flash instead of copying them to SRAM. Without F(): Serial.println('Hello') copies 'Hello' to SRAM. With F(): Serial.println(F('Hello')) reads directly from Flash. Saves 1 byte of SRAM per character. Very significant for string-heavy code.
What is PROGMEM?
PROGMEM is an AVR attribute that stores data in Flash memory instead of SRAM. Used for large tables, lookup arrays, and images. Requires special functions (pgm_read_byte, pgm_read_word) to access. Essential for large datasets on memory-limited boards.
What Arduino board has the most memory?
The Arduino Due (SAM3X8E) has 96KB of SRAM and 512KB Flash. The Arduino Mega 2560 has 8KB SRAM and 256KB Flash. For modern projects needing more memory, Arduino Nano 33 IoT (256KB SRAM) or Nano Every (6KB SRAM, 48KB Flash) are popular choices.