Claude Sonnet 5 vs Claude Sonnet 5.5

As of October 21, 2026, Claude Sonnet 5 and Claude Sonnet 5.5 cost the same: $2.00 per 1M input tokens and $10.00 per 1M output tokens, and both have a 1M-token context window.

Prices from LiteLLM's price fileChecked October 21, 2026

Claude Sonnet 5 vs Claude Sonnet 5.5 side by side

Headline prices in US dollars per 1M tokens: each model's own lab where it sells it, otherwise its cheapest provider. Source: LiteLLM model price file, as of October 21, 2026.
	Claude Sonnet 5	Claude Sonnet 5.5
Input, per 1M tokens	$2.00	$2.00
Output, per 1M tokens	$10.00	$10.00
Cache read, per 1M tokens	$0.20	$0.10
Cache write, per 1M tokens	$2.50	$2.50
Context window	1,000,000 tokens	1,000,000 tokens
Max output	128,000 tokens	128,000 tokens
Image input	Yes	Yes
Tool calling	Yes	Yes
Structured output (JSON)	Yes	Yes
Prompt caching	Yes	Yes
Reasoning	Yes	Yes
Providers on LiteLLM	9	7
Price shown is from	Anthropic	Anthropic
Added to LiteLLM	June 30, 2026	September 28, 2026

Cheapest provider for each

Claude Sonnet 5: Anthropic at $2.00 input and $10.00 output per 1M tokens (claude-sonnet-5)
Claude Sonnet 5.5: Anthropic at $2.00 input and $10.00 output per 1M tokens (claude-sonnet-5-5)

Benchmark scores

From the Epoch AI Benchmarking Hub (CC BY 4.0), data as of September 29, 2026. Some results were run by Epoch and others collected by Epoch from each benchmark's own leaderboard, linked in the first column. Each model's best reported reasoning setting is shown in brackets. Higher is better. Only benchmarks with a score for both models are shown.
Benchmark	Claude Sonnet 5	Claude Sonnet 5.5
Overall
Epoch Capabilities Index	156.9	166.2
Coding and agents
FrontierCode	42.7%	52.1% (xhigh)
APEX-Agents	54.5%	75.5% (max)
Reasoning and knowledge
GPQA Diamond	90.5% (xhigh)	95.6% (max)
SimpleQA Verified	33.7% (max)	46.5% (max)
Math
FrontierMath (tiers 1-3)	65.6% (max)	88.8% (max)
FrontierMath (tier 4)	29.3% (max)	80.5% (max)
OTIS Mock AIME 2024-2025	94.7% (xhigh)	100.0% (max)

Call Claude Sonnet 5 or Claude Sonnet 5.5 with LiteLLM

Both use the OpenAI format through LiteLLM, so switching is a model name change. Set each provider's API key in the environment first.

Python SDK

from litellm import completion

messages = [{"role": "user", "content": "Hello!"}]

# Claude Sonnet 5
response = completion(model="claude-sonnet-5", messages=messages)

# Claude Sonnet 5.5
response = completion(model="claude-sonnet-5-5", messages=messages)

# Claude Sonnet 5, falling back to Claude Sonnet 5.5 if the call fails
response = completion(model="claude-sonnet-5", messages=messages, fallbacks=["claude-sonnet-5-5"])

FAQ

Which is cheaper, Claude Sonnet 5 or Claude Sonnet 5.5?

They cost the same: $2.00 per 1M input tokens and $10.00 per 1M output tokens, as of October 21, 2026.

Which has the larger context window, Claude Sonnet 5 or Claude Sonnet 5.5?

Both have a 1,000,000-token context window.

Can I switch from Claude Sonnet 5 to Claude Sonnet 5.5 without changing my code?

Yes. Through LiteLLM both use the OpenAI format, so switching means changing the model name from "claude-sonnet-5" to "claude-sonnet-5-5", or pointing a LiteLLM gateway model alias at the other model. You can also use one as a fallback for the other.