GPT-5.1 Chat is $3.75 cheaper per 1M input tokens (75% lower; 4x difference).
API cost decision in 10 seconds
Claude Opus 4.5 vs GPT-5.1 Chat
Pick GPT-5.1 Chat for lower cost; pick Claude Opus 4.5 only if the larger context window matters more.
Pricing data updated:
Prices normalized to USD per 1M tokens
Sample workload: 1M input + 500K output
Budget verdict
Pick GPT-5.1 Chat for lower cost; pick Claude Opus 4.5 only if the larger context window matters more.
On the standard 1M input plus 500K output workload, GPT-5.1 Chat is estimated at $6.25 vs $17.5 for Claude Opus 4.5, saving $11.25 (64.3% lower).
Cost-first pickGPT-5.1 Chat
Context-first pickClaude Opus 4.5
Sample savings$11.2564.3%
10x traffic gap$112.5
Claude Opus 4.5 has more context, but GPT-5.1 Chat saves $11.25 on the standard workload. At 10x that traffic, the same price gap is about $112.5. Use the calculator below to replace the sample workload with your own token volume.
Cost sensitivity
Workload Sensitivity
GPT-5.1 Chat stays cheaper across input-heavy, balanced, and output-heavy sample workloads.
| Workload shape | Token mix | Better pick | Claude Opus 4.5 | GPT-5.1 Chat |
|---|---|---|---|---|
| Input-heavy / RAG | 5M input + 500K output | GPT-5.1 Chat | $37.5 | $11.25 |
| Balanced workload | 1M input + 1M output | GPT-5.1 Chat | $30 | $11.25 |
| Output-heavy chatbot | 1M input + 5M output | GPT-5.1 Chat | $130 | $51.25 |
GPT-5.1 Chat is $15 cheaper per 1M output tokens (60% lower; 2.5x difference).
Claude Opus 4.5 has 72K more context (1.56x larger).
GPT-5.1 Chat is $11.25 cheaper on the standard workload (64.3% lower).
Estimate your workload cost
Your Workload Cost
This estimate uses normalized public API pricing per 1M tokens. It is a planning aid, not a billing quote. Verify provider pricing, limits, and terms before production use.
Quick Decision
GPT-5.1 Chat has the lower input price; GPT-5.1 Chat has the lower output price; Claude Opus 4.5 offers the larger context window. For the 1M input plus 500K output sample, GPT-5.1 Chat is cheaper for the standard workload.
For a 1M input token plus 500K output token workload, the estimated API cost is $17.5 for Claude Opus 4.5 and $6.25 for GPT-5.1 Chat.
Choose Claude Opus 4.5 when you care most about larger context window.
Choose GPT-5.1 Chat when you care most about lower input-token price, and lower output-token price.
- On the standard 1M input plus 500K output workload, GPT-5.1 Chat is estimated at $6.25 vs $17.5 for Claude Opus 4.5, saving $11.25 (64.3% lower).
- GPT-5.1 Chat is $11.25 cheaper on the standard workload (64.3% lower).
- GPT-5.1 Chat is $3.75 cheaper per 1M input tokens (75% lower; 4x difference).
- GPT-5.1 Chat is $15 cheaper per 1M output tokens (60% lower; 2.5x difference).
- Claude Opus 4.5 has 72K more context (1.56x larger).
| Feature | Claude Opus 4.5 (Anthropic) | GPT-5.1 Chat (OpenAI) |
|---|---|---|
| Input Price prompt tokens per 1M | $5 | $1.25 |
| Completion Price per 1M tokens | $25 | $10 |
| Sample Workload Cost 1M input + 500K output | $17.5 | $6.25 |
| Context Window | 200K | 128K |
| Release Date |
Use-Case Decision Matrix
| Use case | Better pick | Why |
|---|---|---|
| Budget-constrained production | GPT-5.1 Chat | On the standard 1M input plus 500K output workload, GPT-5.1 Chat is estimated at $6.25 vs $17.5 for Claude Opus 4.5, saving $11.25 (64.3% lower). |
| High-volume input processing | GPT-5.1 Chat | Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill. |
| Long responses and chatbots | GPT-5.1 Chat | Lower output-token price matters most when assistants generate many completion tokens. |
| RAG or long-document work | Claude Opus 4.5 | A larger context window leaves more room for retrieved passages, conversation history, or source files. |
Related Alternatives
- Claude 3 Haiku can replace Claude Opus 4.5 when lower sample workload cost matters most: $0.88.
- Claude 3.5 Haiku can replace Claude Opus 4.5 when lower sample workload cost matters most: $2.8.
- Anthropic Claude Haiku Latest can replace Claude Opus 4.5 when lower sample workload cost matters most: $3.5.
- Claude Haiku 4.5 can replace Claude Opus 4.5 when lower sample workload cost matters most: $3.5.
- Llama 4 Scout offers 10M context with $0.23 sample workload cost.
- Grok 4.20 Multi-Agent offers 2M context with $5 sample workload cost.
- Grok 4.20 offers 2M context with $2.5 sample workload cost.
- OpenAI GPT Latest offers 1.05M context with $20 sample workload cost.
- No popular competitor is currently available.
Cheaper alternatives
Review low-cost models sorted by a standard 1M input plus 500K output workload.
Open cheapest modelsLarger context alternatives
Find models with larger context windows for RAG, long documents, and codebase review.
Open largest context modelsProvider catalogs
Compare models within provider hubs before choosing a final API vendor.
Open provider hubsAnthropic catalog
Review all tracked Anthropic models before deciding whether this matchup is the right shortlist.
Open Anthropic modelsOpenAI catalog
Check other OpenAI models with comparable pricing, context, or release timing.
Open OpenAI modelsClaude Opus 4.5 is Anthropic’s frontier reasoning model optimized for complex software engineering, agentic workflows, and long-horizon computer use. It offers strong multimodal capabilities, competitive performance across real-world coding and...
GPT-5.1 Chat (AKA Instant is the fast, lightweight member of the 5.1 family, optimized for low-latency chat while retaining strong general intelligence. It uses adaptive reasoning to selectively “think” on...