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. Epoch AI has not published a capability index score for Claude Sonnet 5.5 and DeepSeek V4.1 Flash yet.
Prices verified September 28, 2026.
Which should you choose?
Epoch AI has not published a capability index score for Claude Sonnet 5.5 and DeepSeek V4.1 Flash yet.
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.
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 | — |
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 |
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 / request
- Claude Sonnet 5.5Anthropic$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.
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.
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?
- Epoch AI has not published a capability index score for Claude Sonnet 5.5 and DeepSeek V4.1 Flash yet.
- 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.