What is the best alternative to GPT-5.5?

Claude Sonnet 5.5 is the closest model that scores higher on the BenchLeader Index (65.1 against 64.4). For less money, Claude Opus 5.5 scores 69.2 at $8.00 per 1M tokens.

Is there a cheaper alternative to GPT-5.5?

Yes: Claude Opus 5.5 (69.2, $8.00), Gemini 4 Carbon (68.9, $8.00) and GPT-6.1 Sol (67.2, $4.00), each within 4 Index points and cheaper than GPT-5.5's $11.25.

Is there an open-source alternative to GPT-5.5?

The best open-weights models on the BenchLeader Index are Kimi K3 (62.1), GLM-5 (60.2) and GLM 5.2 (60.1). You can download and run them yourself; check each licence on its model page.

How are these alternatives chosen?

From the models ranked on the BenchLeader Index today: the ones just above GPT-5.5, cheaper ones within 4 points, ones at least 1.5× as fast within 4 points, and the best open-weights models. Prices are list prices blended three input tokens to one output.

OpenAI

GPT-5.5 alternatives

Data as of 2 Nov 2026 · ranked on the BenchLeader Index

As of 2 Nov 2026, GPT-5.5 by OpenAI scores 64.4 on the BenchLeader Index at $11.25 per 1M tokens blended. Claude Sonnet 5.5 scores higher (65.1); Claude Opus 5.5 is the best cheaper model within 4 points (69.2 at $8.00); Claude Sonnet 5.5 is at least 1.5× as fast at a similar score; Kimi K3 is the best open-weights option (62.1).

Scores higher

The closest models above GPT-5.5 on the Index.

Claude Sonnet 5.5 Anthropic compare65.1 · $4.00
GPT-6.1 Terra OpenAI compare65.2 · $2.00
Claude Opus 5 Anthropic compare65.4 · $10.00

Cheaper, nearly as good

Within 4 Index points, for less per token.

Claude Opus 5.5 Anthropic compare69.2 · $8.00
Gemini 4 Carbon Google compare68.9 · $8.00
GPT-6.1 Sol OpenAI compare67.2 · $4.00
Gemini 4 Argon Google compare65.9 · $4.00
Claude Opus 5 Anthropic compare65.4 · $10.00

Faster

At least 1.5× the output speed, within 4 points.

Claude Sonnet 5.5 Anthropic compare65.1 · $4.00
GPT-6 Sol OpenAI compare63.5 · $4.00
Gemini 3.5 Flash Google compare62.5 · $3.38

Open weights

The best models whose weights you can run yourself.

Kimi K3 Moonshot AI compare62.1 · $6.00
GLM-5 Zhipu AI60.2 · $1.55
GLM 5.2 Zhipu AI60.1 · $2.15

Every alternative side by side

Model	Index	$ / 1M blended	Tokens / s	Why
GPT-5.5 (this model)	64.4	$11.25	91	–
Claude Opus 5.5	69.2	$8.00	96	cheaper
Gemini 4 Carbon	68.9	$8.00	95	cheaper
GPT-6.1 Sol	67.2	$4.00	87	cheaper
Gemini 4 Argon	65.9	$4.00	83	cheaper
Claude Opus 5	65.4	$10.00	53	scores higher, cheaper
GPT-6.1 Terra	65.2	$2.00	107	scores higher
Claude Sonnet 5.5	65.1	$4.00	137	scores higher, faster
GPT-6 Sol	63.5	$4.00	149	faster
Gemini 3.5 Flash	62.5	$3.38	190	faster
Kimi K3	62.1	$6.00	66	open weights
GLM-5	60.2	$1.55	62	open weights
GLM 5.2	60.1	$2.15	89	open weights

Prices are list prices blended three input tokens to one output; speeds are measured medians, credited on each model page. The Index is BenchLeader's own, from independent benchmarks.

Questions people ask

What is the best alternative to GPT-5.5?: Claude Sonnet 5.5 is the closest model that scores higher on the BenchLeader Index (65.1 against 64.4). For less money, Claude Opus 5.5 scores 69.2 at $8.00 per 1M tokens.
Is there a cheaper alternative to GPT-5.5?: Yes: Claude Opus 5.5 (69.2, $8.00), Gemini 4 Carbon (68.9, $8.00) and GPT-6.1 Sol (67.2, $4.00), each within 4 Index points and cheaper than GPT-5.5's $11.25.
Is there an open-source alternative to GPT-5.5?: The best open-weights models on the BenchLeader Index are Kimi K3 (62.1), GLM-5 (60.2) and GLM 5.2 (60.1). You can download and run them yourself; check each licence on its model page.
How are these alternatives chosen?: From the models ranked on the BenchLeader Index today: the ones just above GPT-5.5, cheaper ones within 4 points, ones at least 1.5× as fast within 4 points, and the best open-weights models. Prices are list prices blended three input tokens to one output.