The OpenAI API applies tier - based differentiated rate limits for developers, encompassing six distinct levels, from the Free tier all the way up to Tier 5. There are notable disparities among these tiers in several key aspects, including the cumulative payment amounts, the duration of account existence, monthly billing ceilings, permissions for model access, and rate limits measured in Requests Per Minute (RPM) and Tokens Per Minute (TPM). Developers in higher tiers are granted access to cutting - edge models such as GPT - 4o and o1 - pro, and they also enjoy larger call quotas. In contrast, developers with lower - tier or free accounts are subject to stringent limitations. For newer models like those in the GPT - 5 series, which boast enhanced performance capabilities, even stricter rate limits are imposed. This necessitates that developers carefully formulate their API call strategies in alignment with their respective account tiers.