Free retro game-dev calculator for GB Studio / NESmaker / Genesis homebrew. Inputs: target system, sprite tile count, background maps, audio tracks, code lines. Outputs: color-coded ROM gauge, bank-boundary warnings, optimization tips.
Built and maintained by Paul Clark, Redmoon Software · Changes and corrections
Use when prototyping a homebrew retro game in GB Studio, NESmaker, or SGDK. Surface the budget problem before you build it.
Compiler error messages tell you after the fact. This tool warns you during planning.
Bytes used ≈ tiles × 16 + maps × 1024 + audio tracks × 4096 + code × 4. A coarse but useful planning estimate.
Each system is checked against one representative cartridge size: Game Boy 32 KB (no bank controller), Game Boy Color 256 KB, NES 128 KB, SNES 1 MB, Genesis 4 MB. Real cartridges with mappers could be larger.
Above the ceiling? Bank-switch your tilesets or compress your audio.
Tiles × 16 bytes, maps × 1 KB, audio × 4 KB, code × 4 bytes/line. It's a planning estimate, not a compiled-binary calculation.
Game Boy VRAM holds ~384 tiles. Above that, you must bank-swap or share tilesets across screens.
No. It compares your total against the whole cartridge size. Older cartridge systems split ROM into fixed-size banks (16 KB on Game Boy, often 8 KB or 16 KB on NES), and code or graphics cannot freely cross a boundary without bank-switching logic, so leave slack in each bank when you lay out real data.
Original Game Boy and NES cartridges commonly ranged from 32KB up to a few hundred KB, while Genesis cartridges scaled into several megabytes. Homebrew tools like GB Studio often impose tighter limits than the hardware maximum.
Input
Game Boy (32 KB), 200 tiles, 8 maps, 6 audio tracks, 500 lines of code.
Output
~37 KB used — over budget!
200 × 16 (tiles) + 8 × 1024 (maps) + 6 × 4096 (audio) + 500 × 4 (code) = 37,968 bytes — already over the 32 KB cartridge limit.
The system sizes here are planning budgets rather than hardware ceilings: 32 KB is what an original Game Boy cartridge holds without a memory bank controller, while 128 KB (NES), 256 KB (Game Boy Color), 1 MB (SNES) and 4 MB (Genesis) are representative cartridge sizes. Mappers went further: the MBC5 controller used on Game Boy Color cartridges addresses up to 8 MB. Even so, those are kilobytes to low megabytes, and a single modern PNG routinely exceeds an entire NES game.
That constraint shaped everything about how those games look. Tile reuse, small palettes, mirrored sprites and procedurally repeated level layouts were not aesthetic choices first; they were what fit. Budgeting a homebrew project against these figures is the fastest way to understand why the era looks the way it does.
Graphics and audio dominate, and audio is the one that surprises people. Sampled audio is impossible at these sizes, which is why the era used sequenced music driving a sound chip — the data is a list of notes and instrument definitions rather than a waveform, and it is orders of magnitude smaller.
Code is usually the smallest of the three. Compression and bank switching both extend the budget, at the cost of decompression time and considerable complexity in the memory map, which is a trade every cartridge of the period was making explicitly.
Optimal grid + VRAM footprint for 2D animations.
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