DeepSeek V4.1 Flash 1017 vs GPT-5.5 Pro: a data-driven comparison

Side-by-side comparison

Criterion	DeepSeek V4.1 Flash 1017	GPT-5.5 Pro
Developer	DeepSeek	OpenAI
Released	October 17, 2026	April 23, 2026
Capability index	90.6 / 100	96.9 / 100
Input price	$0.15	$30
Output price	$0.60	$180
Cost of a typical task	$0.004	$0.96
Context window	1,048,576 tokens	1,050,000 tokens
Maximum output	393,216 tokens	100,000 tokens
Reasoning mode	Yes	Yes
Tool calling	Yes	Yes
Accepted inputs	text, image	text, image, PDF
Open weights	Yes	No
Knowledge cutoff	May 2025	December 1, 2025

The match-up at a glance

This comparison pits the flagship models of two major developers against each other: DeepSeek V4.1 Flash 1017 and GPT-5.5 Pro, one from DeepSeek, the other from OpenAI. The first dates from October 17, 2026, the second from April 23, 2026.

All figures below come from public sources checked on October 22, 2026: models.dev and OpenRouter for prices and capabilities, Epoch AI for scores.

Performance

On our capability index, DeepSeek V4.1 Flash 1017 scores 90.6 out of 100 and GPT-5.5 Pro 96.9. GPT-5.5 Pro leads by 6.3 points.

On the 3 benchmarks reported for both, DeepSeek V4.1 Flash 1017 wins 0 times and GPT-5.5 Pro 3:

GPQA Diamond (PhD-level science questions): DeepSeek V4.1 Flash 1017 93.2%, GPT-5.5 Pro 93.9%
OTIS Mock AIME (competition mathematics problems): DeepSeek V4.1 Flash 1017 99.4%, GPT-5.5 Pro 100%
FrontierMath (very hard research-level mathematics): DeepSeek V4.1 Flash 1017 71.2%, GPT-5.5 Pro 87.7%

Budget

DeepSeek V4.1 Flash 1017 costs $0.15 per million input tokens and $0.60 per million output tokens; GPT-5.5 Pro costs $30 and $180.

For a typical agent task (read 20,000 tokens, write 2,000), expect $0.004 with DeepSeek V4.1 Flash 1017 versus $0.96 with GPT-5.5 Pro. DeepSeek V4.1 Flash 1017 is 228.6 times cheaper, a gap that adds up quickly over 1,000 tasks: $955.8 difference.

Run the numbers with your own volumes in the agent cost calculator.

Features and limits

GPT-5.5 Pro reads more in one go: 1,050,000 tokens of context (roughly 1,575 pages), versus 1,048,576 for DeepSeek V4.1 Flash 1017.

Reasoning mode: DeepSeek V4.1 Flash 1017 yes, GPT-5.5 Pro yes. Tool calling: DeepSeek V4.1 Flash 1017 yes, GPT-5.5 Pro yes. Image input: DeepSeek V4.1 Flash 1017 yes, GPT-5.5 Pro yes.

DeepSeek V4.1 Flash 1017 publishes its weights and can run on your servers; GPT-5.5 Pro is a closed model, available only through an API.

Knowledge cutoff: May 2025 for DeepSeek V4.1 Flash 1017, December 1, 2025 for GPT-5.5 Pro.

In short

Our reading of the data:

Choose DeepSeek V4.1 Flash 1017 for a lower cost, open weights (you can host it yourself) and a more recent release.
Choose GPT-5.5 Pro for a higher capability index.

This verdict relies on public figures; it does not replace a trial on your own tasks.

Frequently asked questions

DeepSeek V4.1 Flash 1017 or GPT-5.5 Pro: which is better?

On our index (Epoch AI data), DeepSeek V4.1 Flash 1017 scores 90.6 and GPT-5.5 Pro 96.9 out of 100. The best choice also depends on price and on your use case.

Which one is cheaper?

DeepSeek V4.1 Flash 1017. To read 20,000 tokens and write 2,000, expect $0.004 with DeepSeek V4.1 Flash 1017 and $0.96 with GPT-5.5 Pro (prices as of October 22, 2026).

Which one has the larger context window?

GPT-5.5 Pro, with 1,050,000 tokens versus 1,048,576.

Can I run DeepSeek V4.1 Flash 1017 or GPT-5.5 Pro on my own servers?

Only DeepSeek V4.1 Flash 1017, whose weights are published. GPT-5.5 Pro is used through an API.

DeepSeek V4.1 Flash 1017 versus GPT-5.5 Pro