GPT-5.4 Mini vs GPT-5.4 Nano

Both are the budget end of the GPT-5.4 generation, and the gap between them is a genuine step, not a rounding difference — Mini costs meaningfully more than Nano at every tier, in exchange for real differences beyond just a bigger number on the price table.

The rate-limit split is the one to check first

Mini shares its rate-limit group with the cheapest current GPT-5.6 model, carrying a comparatively generous top-tier ceiling. Nano sits in its own distinct group, with a Tier-1 token-per-minute ceiling under half of most other current models' — including Mini's. For a high-volume workload, that gap in headroom can matter more than the per-token price difference between them.

Fast mode is the other split

Mini publishes a Fast-mode tier at a premium over its Standard rate. Nano doesn't offer Fast at all — Standard is the fastest paid option available for it, full stop.

How to actually decide

For genuinely simple, high-volume calls where Nano's price is the whole appeal, check its Tier-1 TPM ceiling against your actual request rate before committing — the ceiling, not the price, is the more likely constraint at real volume. For anything where low-latency Fast-mode delivery matters even occasionally, Mini is the only one of the two that offers it at all, which settles the choice regardless of the price gap — there's no version of Nano that gets you that option at any price.