GPT-5.6 Luna vs GPT-6 Sol: pricing and benchmarks
GPT-5.6 Luna is 90% cheaper on input tokens ($0.20 vs $2.00 per 1M). GPT-5.6 Luna is 88% cheaper on output tokens ($1.20 vs $10.00 per 1M). On our document Q&A workload (50,000 questions a month), GPT-5.6 Luna costs $116.00 a month versus $1,100 for GPT-6 Sol, 89% less. Epoch AI has not published a capability index score for GPT-6 Sol yet.
Prices verified September 26, 2026.
Which should you choose?
Epoch AI has not published a capability index score for GPT-6 Sol yet.
GPT-5.6 Luna costs $0.45 per 1M tokens (3:1 input-to-output mix) vs $4.00 for GPT-6 Sol, 89% less.
Pricing and specs
| GPT-5.6 Luna | GPT-6 Sol | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| API model ID | gpt-5.6-luna | gpt-6-sol |
| Input / 1M tokens | $0.20 | $2.00 |
| Cached input / 1M tokens | $0.02 | $0.20 |
| Output / 1M tokens | $1.20 | $10.00 |
| Long-context rates | $0.40 in / $1.80 out on long-context requests | $4.00 in / $15.00 out on long-context requests |
| Context window | 1.05M tokens | 1.05M tokens |
| Max output | 128K tokens | 128K tokens |
| Batch discount | 50% off | 50% off |
Benchmarks
| GPT-5.6 Luna | GPT-6 Sol | |
|---|---|---|
| Epoch Capabilities Index | 156.3 | — |
| GPQA Diamond· Science reasoning | 88.8% | — |
| FrontierMath (Tiers 1–3)· Advanced math | 82.1% | — |
| SimpleQA Verified· Factual accuracy | 41.0% | — |
| ARC-AGI-2· Abstract reasoning | 59.5% | — |
| DeepSWE· Coding | 67.2% | — |
| APEX-Agents· Agentic work | — | — |
Source: Epoch AI, best recorded result per model (CC BY 4.0). A dash means no published score. See all benchmarks
Monthly cost for real workloads
| Workload | GPT-5.6 Luna | GPT-6 Sol | Difference |
|---|---|---|---|
Support chatbot 100,000 replies a month, ~1,500 input tokens (system prompt + history) and ~400 output tokens each. | $78.00 | $700.00 | GPT-5.6 Luna 89% cheaper |
Document Q&A (RAG) 50,000 questions a month with ~8,000 tokens of retrieved context and ~600 output tokens each. | $116.00 | $1,100 | GPT-5.6 Luna 89% cheaper |
Coding agent 10,000 agent steps a month, ~40,000 input tokens each (70% read from the prompt cache) and ~2,000 output tokens. | $53.60 | $496.00 | GPT-5.6 Luna 89% cheaper |
Estimates use standard list prices and ignore cache-write surcharges. Different tokenizers can count the same text differently, so test with your own prompts.
GPT-5.6 Luna vs GPT-6 Sol cost calculator
- $116.00/mo$0.0023 / request
- GPT-6 SolOpenAI$1,100/mo$0.02 / request
Standard-tier list prices. Long-context rates apply automatically where the provider publishes a threshold. Excludes cache-write surcharges, taxes, batch and volume discounts.
GPT-5.6 Luna pricing notes
The GPT-5.6 model optimized for cost-sensitive, high-volume workloads.
- Cache writes are billed at $0.25 per 1M tokens.
- Fast mode costs 2x the standard rate; Flex costs half.
GPT-6 Sol pricing notes
OpenAI’s GPT-6 model built to power complex coding and agentic workflows.
- Cache writes are billed at $2.50 per 1M tokens.
- Fast mode costs 2x the standard rate; Flex costs half.
- Regional (data residency) endpoints add a 10% uplift, and EU data residency is available only with standard processing.
Frequently asked questions
- Is GPT-5.6 Luna cheaper than GPT-6 Sol?
- GPT-5.6 Luna is 90% cheaper on input tokens ($0.20 vs $2.00 per 1M). GPT-5.6 Luna is 88% cheaper on output tokens ($1.20 vs $10.00 per 1M). On our document Q&A workload (50,000 questions a month), GPT-5.6 Luna costs $116.00 a month versus $1,100 for GPT-6 Sol, 89% less.
- Which is more capable, GPT-5.6 Luna or GPT-6 Sol?
- Epoch AI has not published a capability index score for GPT-6 Sol yet.
- How much does GPT-5.6 Luna cost per 1M tokens?
- GPT-5.6 Luna costs $0.20 per 1M input tokens and $1.20 per 1M output tokens, and $0.02 per 1M cached input tokens on OpenAI’s standard tier.
- How much does GPT-6 Sol cost per 1M tokens?
- GPT-6 Sol costs $2.00 per 1M input tokens and $10.00 per 1M output tokens, and $0.20 per 1M cached input tokens on OpenAI’s standard tier.
- Which has the larger context window, GPT-5.6 Luna or GPT-6 Sol?
- Both offer a 1.05M-token context window.