GPT-4o vs GPT-4.1: Pricing, Performance, and When to Use Each (March 2026)
GPT-4o and GPT-4.1 are OpenAI's two current mid-tier flagships. They perform at similar levels on most text tasks, have the same context window (128K tokens), and the wrong default costs you 20% more on every API call.
The quick answer: GPT-4o costs $2.50/1M input and $10.00/1M output. GPT-4.1 costs $2.00/1M input and $8.00/1M output — about 20% less across the board. For text-only workloads, you should be benchmarking GPT-4.1 as your default.
The pricing gap at scale
At 1 million requests per month averaging 500 input tokens and 500 output tokens each: GPT-4o costs $1.25 on input and $5.00 on output, totalling $6.25 per million requests. GPT-4.1 costs $1.00 and $4.00, totalling $5.00 per million requests. That is $1.25 saved per million requests, or $12,500/month at 10 million requests. The only change is the model ID in your API call.
Most teams default to GPT-4o because it is the familiar flagship. For text-only workloads, that habit costs 20% of the AI bill every month with no quality benefit.
When GPT-4o is the right choice
GPT-4o is OpenAI's multimodal model — it handles text, images, audio, and vision natively. Use GPT-4o when your application requires image analysis or document OCR with visual elements, vision-based tasks like interpreting screenshots or diagrams, real-time audio processing, or any workflow where the input is not plain text. GPT-4.1 does not have the same native multimodal capabilities.
GPT-4o is also the standard for streaming chat interfaces where response feel has been tuned over time. If you are running a customer-facing real-time chat product and have not benchmarked GPT-4.1 as a drop-in, that test is worth running — but GPT-4o remains the safe default for multimodal applications.
When GPT-4.1 is the better choice
GPT-4.1 performs comparably to GPT-4o on most text tasks and costs 20% less. OpenAI designed it for general-purpose text workflows with stronger instruction-following and reduced verbosity. It is the right model for document analysis and summarisation, code generation and review, API integrations with structured output, multi-turn text conversations, and classification or extraction at scale. If your input is not an image, start here.
Do not overlook the mini tier
The larger cost lever is not GPT-4o vs GPT-4.1 — it is whether you are routing simple tasks to a mini model at all. GPT-4o mini costs $0.15/1M input and $0.60/1M output — 16× cheaper on input than GPT-4o. GPT-4.1 mini is $0.40/1M input and $1.60/1M output.
Routing even half your requests from a flagship to a mini model — for tasks like classification, extraction, or simple Q&A — saves more than switching between GPT-4o and GPT-4.1 at the flagship tier. The question is not just which flagship to use; it is which requests actually need a flagship at all.
If you want to understand which customers and features are driving your current OpenAI spend before you start routing, PerUnit breaks it down by customer, feature, and pricing tier. Or run the numbers with our free AI cost calculator.