Step 3.5 Flash vs DeepSeek V4.1 Flash
Official StepFun and DeepSeek API prices and LMArena scores, checked 2026-11-01. Add up to 2 more models to compare 4.
Step 3.5 Flash costs less; DeepSeek V4.1 Flash wins more LMArena tasks.
Step 3.5 Flash is 3x cheaper on input and 4x cheaper on output. DeepSeek V4.1 Flash scores 40 points higher for reasoning and math. Across 4 shared LMArena tasks, DeepSeek V4.1 Flash leads 2 to 0 (2 tied). A medium month (20M input + 5M output tokens) costs $3.50 on Step 3.5 Flash and $12 on DeepSeek V4.1 Flash.
- Pick Step 3.5 Flash if you want the lower bill ($3.50 vs $12 for a medium month).
- Pick DeepSeek V4.1 Flash if you care most about reasoning and math (+40) and chat (+17) or you reuse long prompts (cached input $0.006 vs $0.02).
Medium: 20M input + 5M output tokens a month at list price (short-context rate, no caching or batch discounts).
Marked side is better: lower for prices, higher for context and scores. Bars are scaled to the larger of the two.
| Spec | Step 3.5 Flash | DeepSeek V4.1 Flash |
|---|---|---|
| Price per 1M tokens | ||
| Input | $0.10 | $0.30 |
| Cached input | $0.02 | $0.006 |
| Output | $0.30 | $1.20 |
| Blend 3:1 | $0.15 | $0.525 |
| Sample month, medium | $3.50 | $12 |
| Context | ||
| Context window | Not published | 1M tokens |
| Quality (LMArena, out of 100) | ||
| Coding | Not ranked | 46/100 #12 of 50 |
| Chat | 0/100 #51 of 51 | 17/100 #18 of 51 |
| Creative writing | 0/100 #49 of 51 | 0/100 #22 of 51 |
| Roleplay and characters | 0/100 #49 of 51 | 0/100 #24 of 51 |
| Reasoning and math | 0/100 #49 of 51 | 40/100 #14 of 51 |
| Vision | Not ranked | 14/100 #19 of 33 |
| Long documents | Not ranked | Not ranked |
| Cheap bulk and agents | Not ranked | 39/100 #14 of 37 |
| Details | ||
| Provider | StepFun | DeepSeek |
| API model id | step-3.5-flash | deepseek-flash |
| Notes | None | Peak rate. Off-peak is half price. |
| Sources | ||
| Last checked | 2026-11-01 | 2026-11-01 |
| Official pricing | StepFun pricing | DeepSeek pricing |
Plans from data checked hourly against each vendor's official pricing page. Vendors state limits in different units, so we quote them as published. Team and enterprise plans are per seat.
API prices in USD per 1M tokens from each provider's official pricing page. Blend 3:1 = (3 x input + output) / 4. Sample month = stated input and output tokens at the list price, no caching. Quality: relative score out of 100 on each LMArena leaderboard (100 = top model we price on that board, n/a = not ranked there), data licensed CC BY 4.0. See how we pick.
Where each one ranks on LMArena
Relative score out of 100 on each leaderboard (100 = the top model we price there), with the rank among the models from our API price table that appear on that board.
- Coding (Code Arena): Step 3.5 Flash not ranked, DeepSeek V4.1 Flash #12 of 50 (46/100)
- Chat (Text Arena): Step 3.5 Flash #51 of 51 (0/100), DeepSeek V4.1 Flash #18 of 51 (17/100)
- Creative writing (Text Arena creative writing): Step 3.5 Flash #49 of 51 (0/100), DeepSeek V4.1 Flash #22 of 51 (0/100)
- Roleplay and characters (Text Arena multi-turn): Step 3.5 Flash #49 of 51 (0/100), DeepSeek V4.1 Flash #24 of 51 (0/100)
- Reasoning and math (Text Arena math): Step 3.5 Flash #49 of 51 (0/100), DeepSeek V4.1 Flash #14 of 51 (40/100)
- Vision (Vision Arena): Step 3.5 Flash not ranked, DeepSeek V4.1 Flash #19 of 33 (14/100)
- Long documents (Document Arena): Step 3.5 Flash not ranked, DeepSeek V4.1 Flash not ranked
- Cheap bulk and agents (Agent Arena): Step 3.5 Flash not ranked, DeepSeek V4.1 Flash #14 of 37 (39/100)
Pricing details from the official pages
Step 3.5 Flash lists $0.10 input, $0.30 output, $0.02 cached input per 1M tokens on StepFun pricing. DeepSeek V4.1 Flash lists $0.30 input, $1.20 output, $0.006 cached input per 1M tokens on DeepSeek pricing. Prices checked 2026-11-01.
- DeepSeek V4.1 Flash: Peak rate. Off-peak is half price.
Sample monthly bill at list price, no caching: Light (2M input + 0.5M output tokens): $0.35 vs $1.20. Medium (20M input + 5M output tokens): $3.50 vs $12. Heavy (200M input + 50M output tokens): $35 vs $120.
FAQ
Is Step 3.5 Flash cheaper than DeepSeek V4.1 Flash?
Step 3.5 Flash costs $0.10 input and $0.30 output per 1M tokens; DeepSeek V4.1 Flash costs $0.30 and $1.20. For a medium month (20M input + 5M output tokens) Step 3.5 Flash is cheaper: $3.50 vs $12.
Which is better for coding, Step 3.5 Flash or DeepSeek V4.1 Flash?
Code Arena score: Step 3.5 Flash n/a (not ranked), DeepSeek V4.1 Flash 46/100. We do not guess missing scores.
Which has the bigger context window?
Step 3.5 Flash: n/a. DeepSeek V4.1 Flash: 1M tokens.
How much do Step 3.5 Flash and DeepSeek V4.1 Flash cost per month?
Light (2M input + 0.5M output tokens): $0.35 vs $1.20. Medium (20M input + 5M output tokens): $3.50 vs $12. Heavy (200M input + 50M output tokens): $35 vs $120. Pick your own token counts in the plan vs API calculator.
Where do these numbers come from?
Prices come from each provider's official pricing page, checked daily. Quality is the relative score on the LMArena leaderboard dataset, licensed CC BY 4.0. Where a model is not ranked we show n/a.
Sources
Related
- Cheapest LLM APIs, compared
- StepFun API pricing, every model
- DeepSeek API pricing, every model
- DeepSeek V4.1 Flash vs Gemini 3.8 Flash
- MiniMax-M3 vs DeepSeek V4.1 Flash
- DeepSeek V4.1 Flash vs GPT-6 Luna
- DeepSeek V4.1 Flash vs Claude Haiku 5.5
- DeepSeek V4.1 Flash vs Qwen3.8 Flash
- Seed 2.1 Turbo vs DeepSeek V4.1 Flash
- AI API prices, all models