MCU Display RAM & Frame Buffer Calculator
Estimate how much RAM a microcontroller needs to drive a display: full frame buffers for RGB panels, or partial draw buffers for SPI and MCU-interface panels with their own display memory, as used by graphics libraries such as LVGL. Everything runs in your browser.
1. Display and buffering
2. Results
| One full frame | – |
|---|---|
| Full frame buffers | – |
| Draw buffers | – |
| Total display RAM | – |
| Fits in internal SRAM of | – |
Display RAM only: the graphics library, fonts, images and the application need memory too. Panels with an RGB interface have no frame memory of their own, so the host must keep at least one full frame. SPI and 8080/MCU-interface panels usually include a controller with GRAM, so the host can work with partial draw buffers.
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How the calculator works
One frame takes width × height × bits per pixel ÷ 8 bytes: an 800×480 RGB565 frame is 768,000 bytes (750 KB), and a 128×64 monochrome frame is 1,024 bytes. Double buffering doubles the frame-buffer memory but lets the next frame be drawn while the current one is displayed.
Graphics libraries such as LVGL can render into smaller draw buffers and send the finished areas to the display. LVGL’s documentation suggests about 1/10 of the screen as a starting point, and two draw buffers let rendering and transfer overlap. This works when the panel keeps the image in its own controller memory, which is the usual case for SPI and 8080/MCU-interface displays.
An RGB-interface panel is refreshed continuously by the host’s LCD controller from a full frame buffer, so the host needs at least one frame in RAM, often in external SDRAM or PSRAM for 800×480 and larger screens. With two full frame buffers, the library can usually render straight into them, so separate draw buffers are optional; with one frame buffer, small draw buffers are rendered and then copied into it.
Small monochrome OLED and LCD modules such as 128×64 are often driven with a full 1 KB frame buffer in the MCU, because many of their controllers cannot read display memory back over I²C or SPI; the presets reflect these typical set-ups.
Frequently asked questions
How much RAM does an 800×480 RGB565 display need?
One frame is 750 KB and double buffering needs about 1.5 MB, which is more than the internal SRAM of most microcontrollers, so these designs usually add external SDRAM or PSRAM.
Why can a small MCU drive a 240×320 SPI display?
The display controller holds the image in its own GRAM. The MCU only needs a partial draw buffer: 1/10 of a 240×320 RGB565 screen is 15 KB.
Does colour depth change the memory needed?
Yes. Memory scales with bits per pixel: RGB888 uses 1.5 times and ARGB8888 twice the memory of RGB565 for the same resolution.