Claude Sonnet 5.5 vs DeepSeek V4.1 Flash: pricing and benchmarks
DeepSeek V4.1 Flash is 85% cheaper on input tokens ($0.30 vs $2.00 per 1M). DeepSeek V4.1 Flash is 88% cheaper on output tokens ($1.20 vs $10.00 per 1M). On our document Q&A workload (50,000 questions a month), DeepSeek V4.1 Flash costs $156.00 a month versus $1,100 for Claude Sonnet 5.5, 86% less. Claude Sonnet 5.5 scores 164.4 on the Epoch Capabilities Index vs 155.6 for DeepSeek V4.1 Flash.
Which should you choose?
Claude Sonnet 5.5 scores 164.4 on the Epoch Capabilities Index vs 155.6 for DeepSeek V4.1 Flash.
Claude Sonnet 5.5 scores 88.8% on FrontierMath (Tiers 1–3) vs 67.4% for DeepSeek V4.1 Flash.
DeepSeek V4.1 Flash costs $0.525 per 1M tokens (3:1 input-to-output mix) vs $4.00 for Claude Sonnet 5.5, 87% less.
A trade-off: Claude Sonnet 5.5 is 8.9 ECI points more capable but costs 7.6x as much as DeepSeek V4.1 Flash.
Pricing and specs
| Claude Sonnet 5.5 | DeepSeek V4.1 Flash | |
|---|---|---|
| Provider | Anthropic | DeepSeek |
| API model ID | claude-sonnet-5-5 | deepseek-flash |
| Input / 1M tokens | $2.00 | $0.30 |
| Cached input / 1M tokens | $0.20 | $0.006 |
| Output / 1M tokens | $10.00 | $1.20 |
| Long-context rates | — | — |
| Context window | 1M tokens | 1M tokens |
| Max output | 128K tokens | 384K tokens |
| Batch discount | 50% off | — |
Benchmarks
| Claude Sonnet 5.5 | DeepSeek V4.1 Flash | |
|---|---|---|
| Epoch Capabilities Index | 164.4 | 155.6 |
| GPQA Diamond· Science reasoning | 95.6% | 89.8% |
| FrontierMath (Tiers 1–3)· Advanced math | 88.8% | 67.4% |
| SimpleQA Verified· Factual accuracy | 46.5% | 42.9% |
| ARC-AGI-2· Abstract reasoning | — | 72.9% |
| DeepSWE· Coding | — | — |
| APEX-Agents· Agentic work | 75.5% | 39.5% |
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 | Claude Sonnet 5.5 | DeepSeek V4.1 Flash | Difference |
|---|---|---|---|
Support chatbot 100,000 replies a month, ~1,500 input tokens (system prompt + history) and ~400 output tokens each. | $700.00 | $93.00 | DeepSeek V4.1 Flash 87% cheaper |
Document Q&A (RAG) 50,000 questions a month with ~8,000 tokens of retrieved context and ~600 output tokens each. | $1,100 | $156.00 | DeepSeek V4.1 Flash 86% 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. | $496.00 | $61.68 | DeepSeek V4.1 Flash 88% cheaper |
Cached chatbot The same 100,000-reply support chatbot, but 60% of each prompt (system prompt + conversation history) is served from the prompt cache. | $538.00 | $66.54 | DeepSeek V4.1 Flash 88% cheaper |
Meeting notes 10,000 meetings a month summarized from ~12,000-token transcripts, ~1,000 output tokens each. | $340.00 | $48.00 | DeepSeek V4.1 Flash 86% cheaper |
Bulk translation 200,000 short translations a month, ~800 input and ~800 output tokens each. | $1,920 | $240.00 | DeepSeek V4.1 Flash 88% cheaper |
Content moderation 1,000,000 classifications a month, ~400 input tokens and ~80 output tokens each. | $1,600 | $216.00 | DeepSeek V4.1 Flash 87% cheaper |
Article drafting 300 long-form articles a month written from a ~4,000-token brief and outline, ~5,000 output tokens each. | $17.40 | $2.16 | DeepSeek V4.1 Flash 88% cheaper |
Code review bot 30,000 pull-request reviews a month, ~5,000 input tokens each (30% cached repository context) and ~700 output tokens. | $429.00 | $56.97 | DeepSeek V4.1 Flash 87% cheaper |
Invoice extraction 100,000 documents a month parsed into structured JSON, ~1,200 input and ~250 output tokens each. | $490.00 | $66.00 | DeepSeek V4.1 Flash 87% 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.
Claude Sonnet 5.5 vs DeepSeek V4.1 Flash cost calculator
- $156.00/mo$0.0031 / req
- Claude Sonnet 5.5Anthropic$1,100/mo$0.02 / req
Standard-tier list prices. Long-context rates apply automatically where the provider publishes a threshold. Excludes cache-write surcharges, taxes, batch and volume discounts.
Claude Sonnet 5.5 pricing notes
Anthropic’s fast mid-tier model, successor to Claude Sonnet 5 at the same price.
- Cache writes cost $2.50 (5-minute cache) or $4 (1-hour cache) per 1M tokens.
- US-only inference (inference_geo: "us") costs 1.1x.
DeepSeek V4.1 Flash pricing notes
DeepSeek’s low-cost model with thinking and non-thinking modes, tool calls and vision input.
- Prices shown are peak rates. Off-peak rates are half: peak hours are 01:00–04:00 and 06:00–10:00 UTC, Monday to Friday.
- Compatible with both OpenAI-format and Anthropic-format APIs.
- Served by model version DeepSeek-V4.1-Flash-1017; the legacy names deepseek-v4-flash and deepseek-v4-flash-vision-exp route to it at the same price.
- Web Search and Fetch cost $0.75 per 1,000 successful requests each; calls made through Claude Code, Codex or DeepSeek Harness are free until November 1, 2026.
Frequently asked questions
- Is Claude Sonnet 5.5 cheaper than DeepSeek V4.1 Flash?
- DeepSeek V4.1 Flash is 85% cheaper on input tokens ($0.30 vs $2.00 per 1M). DeepSeek V4.1 Flash is 88% cheaper on output tokens ($1.20 vs $10.00 per 1M). On our document Q&A workload (50,000 questions a month), DeepSeek V4.1 Flash costs $156.00 a month versus $1,100 for Claude Sonnet 5.5, 86% less.
- Which is more capable, Claude Sonnet 5.5 or DeepSeek V4.1 Flash?
- Claude Sonnet 5.5 scores 164.4 on the Epoch Capabilities Index vs 155.6 for DeepSeek V4.1 Flash.
- How much does Claude Sonnet 5.5 cost per 1M tokens?
- Claude Sonnet 5.5 costs $2.00 per 1M input tokens and $10.00 per 1M output tokens, and $0.20 per 1M cached input tokens on Anthropic’s standard tier.
- How much does DeepSeek V4.1 Flash cost per 1M tokens?
- DeepSeek V4.1 Flash costs $0.30 per 1M input tokens and $1.20 per 1M output tokens, and $0.006 per 1M cached input tokens on DeepSeek’s standard tier.
- Which has the larger context window, Claude Sonnet 5.5 or DeepSeek V4.1 Flash?
- Both offer a 1M-token context window.