Which is more cost-effective, Claude Sonnet 5.5 or GPT-6.1 Terra?

Based on 1M input + 1M output tokens, Claude Sonnet 5.5 costs $12.00/month versus GPT-6.1 Terra at $6.00/month. The cheaper option depends on your token volume and prompt-to-completion ratio. Use the interactive calculator on this page to enter your exact usage.

How accurate is this cost comparison?

List prices come from each provider's own pricing page and every model page shows when they were last verified. The capability scores are iOPTERA's editorial composites — informed by public benchmarks, not benchmark results themselves; the methodology page explains how they are set.

Which model scores higher on benchmarks?

Claude Sonnet 5.5 scores 97 in coding and 94 in reasoning benchmarks. GPT-6.1 Terra scores 94 in coding and 95 in reasoning. See the full 5-category breakdown in the Benchmark Comparison section above.

What are the context window sizes of Claude Sonnet 5.5 and GPT-6.1 Terra?

Claude Sonnet 5.5 supports a 1.0M-token context window while GPT-6.1 Terra supports 1.1M tokens. A larger context window lets you process more text in a single API call.

Which model is faster for real-time applications?

Claude Sonnet 5.5 has a speed score of 91/100 and GPT-6.1 Terra scores 90/100 on our latency benchmark. For interactive chatbots and low-latency tasks, the higher speed score is preferable.

Can I calculate costs for my specific token volume?

Yes. Use the interactive cost calculator on this page. Enter your monthly token volume and adjust the prompt-to-completion ratio. You can also use presets for common scenarios like Customer Support Bots (~30M tokens/month) or Document Summarizers (~15M tokens/month).

Cost and performance comparison

Claude Sonnet 5.5 vs GPT-6.1 Terra

Model AAnthropic

Claude Sonnet 5.5

Capability score (editorial)94/100

Cost / 1M Tokens: $4.40; 70% in · 30% out mix; ≈ $6.29 for the same text, tokenizer included
Value Index (score÷cost): 14.9; Higher = better value

Speed: 91/100
Context: 1.0M
Tier: Smart Tier

List price from the Anthropic pricing page, verified November 9, 2026.

Its tokenizer produces about 43% more tokens than OpenAI's for the same text, so the real cost runs higher than the list price suggests. This is an estimate: the tokenizer has not been measured yet.

Check the source

How we verify prices

Model BOpenAI

GPT-6.1 Terra

Capability score (editorial)95/100

Cost / 1M Tokens: $2.20; 70% in · 30% out mix
Value Index (score÷cost): 43.2; Higher = better value

Speed: 90/100
Context: 1.1M
Tier: Smart Tier

List price from the OpenAI pricing page, verified November 9, 2026.

Check the source

How we verify prices

In-depth analysis

Claude Sonnet 5.5 vs GPT-6.1 Terra: Detailed Comparison

Claude Sonnet 5.5 is Anthropic's mid-range-tier language model with a 1.0M-token context window, excelling at coding. GPT-6.1 Terra from OpenAI is a mid-range-tier model supporting 1.1M tokens in context, with standout performance in reasoning.

Claude Sonnet 5.5 costs 2.9x what GPT-6.1 Terra does for the same text. That is a steep premium, and it buys a 2-point lead on combined coding and reasoning. Whether that trade is worth it depends entirely on how much of your traffic actually needs the harder model — for most workloads the honest answer is a small fraction of it, which is an argument for routing rather than for picking one. Claude Sonnet 5.5 is priced at $2.00/M input tokens and $10.00/M output tokens. GPT-6.1 Terra costs $1.00/M input and $5.00/M output.

Claude Sonnet 5.5 turns the same text into about 43% more tokens than GPT-6.1 Terra, because their tokenizers differ — so comparing list prices per token understates what Claude Sonnet 5.5 costs. For the same text, split 70% input and 30% output and counted the way OpenAI's tokenizer counts it, Claude Sonnet 5.5 works out at about $6.29 per million tokens and GPT-6.1 Terra at $2.20. Every cost figure on this page includes that difference.

On iOPTERA's editorial scores, Claude Sonnet 5.5 leads with 97/100 for coding and 94/100 for reasoning, against GPT-6.1 Terra's 94/100 and 95/100.

Capability breakdown

Across the five core benchmark categories, here is how Claude Sonnet 5.5 and GPT-6.1 Terra stack up head to head:

coding

Claude Sonnet leads

reasoning

GPT-6.1 Terra leads

data extraction

Tie

creative tasks

Tie

vision/multimodal

GPT-6.1 Terra leads

Best model by task

coding: Claude Sonnet 5.5 wins with 97/100
reasoning: GPT-6.1 Terra wins with 95/100
vision/multimodal: GPT-6.1 Terra wins with 94/100

Estimated monthly cost at scale

For 10M + 2M tokens of text a month (counted the way OpenAI's tokenizer counts), Claude Sonnet 5.5 runs about $57.20 while GPT-6.1 Terra runs about $20.00 — GPT-6.1 Terra saves roughly $37.20 (65%) every month.

What actually decides it

Claude Sonnet 5.5 and GPT-6.1 Terra come from different labs, which means different tokenizers, different API shapes, and a second vendor relationship. The same English text does not produce the same token count on both, so a price-per-million comparison understates the difference — measure your own prompts on each before treating the headline rates as the full story.

GPT-6.1 Terra and Claude Sonnet 5.5 were released within 1 months of each other, so they are competing on the same evaluations under roughly the same conditions. That makes a direct benchmark comparison meaningful here in a way it usually is not — neither model has the advantage of being measured on a newer, easier set of tests.

Context is effectively a tie: 1.1M against 1.0M. Neither model unlocks a document size the other cannot handle, so this axis should not enter the decision. If you were hoping context would break the tie for you, it will not.

Throughput is close enough to ignore — 91/100 versus 90/100. Neither model will feel noticeably quicker in an interactive product, so latency is not a reason to choose between them.

Claude Sonnet 5.5 is 2.9x the price of GPT-6.1 Terra. Reserve it for the requests that actually need it and route the rest to GPT-6.1 Terra — that hybrid beats either model used alone on cost per useful answer.

What you actually pay

The list price is only the start. Prompt caching, batch processing and long prompts change the bill, and each provider sets them differently. Prices per 1M tokens.

Pricing terms beyond the list price, per 1M tokens
Pricing term	Claude Sonnet 5.5	GPT-6.1 Terra
List price (input / output)	$2.00 / $10.00	$1.00 / $5.00
Cached input	$0.105% of the input price	$0.055% of the input price
Batch API	50% off input and output	50% off input and output
Long prompts	No surcharge across the 1M window	Over 272K tokens: $2.00 / $7.50
Input with 80% cache hits	$0.48	$0.24

With 80% of input served from the cache, GPT-6.1 Terra costs 65% less than Claude Sonnet 5.5 for the same input text, counting each model's tokenizer.The tokenizer factor for Claude Sonnet 5.5 is our estimate until it is measured.

The last row assumes 80% of input tokens are read from the cache, as in a chat app that re-sends a long system prompt or RAG over the same documents. Cache-write and storage charges are not included.

Claude also bills cache writes: 1.25× the input price for a 5-minute cache, 2× for one hour.

Checked on October 8, 2026 against the pricing pages of Anthropic, OpenAI.

Capability scores

iOPTERA editorial scores across 5 categories — informed by public benchmarks, not measured by us

CategoryClaude SonnetGPT-6.1 TerraWinner

Coding

Reasoning

Extraction

Tied

Creative

Tied

Vision

Claude Sonnet 5.5: 1 wins

GPT-6.1 Terra: 2 wins

GPT-6.1 Terra leads overall

Speed Score

91/100vs90/100

ClaudeGPT-6.1

Context Window

1000Kvs1050K

ClaudeGPT-6.1

What Is a Token?

Models don't read words — they process tokens.

A token is roughly 4 characters of English text (~¾ of a word). Your API bill is priced per million tokens — understanding this directly reduces your costs.

Short phrase

"Hello, world!"

4 tokens

Claude Sonnet 5.5: $1.14
GPT-6.1 Terra: $0.40

Business email

One typical email (~200 words)

~270 tokens

Claude Sonnet 5.5: $77.22
GPT-6.1 Terra: $27.00

Code file

50-line Python script

~400 tokens

Claude Sonnet 5.5: $114.40
GPT-6.1 Terra: $40.00

Prices shown are for 100,000 runs of each workload — one run costs a fraction of a cent on both Claude Sonnet 5.5 and GPT-6.1 Terra, so the number only becomes meaningful at production volume. Input tokens only; add your output volume in the calculator below.

How to check your token usage

response.usage.total_tokens

Every API response includes a usage object. Sum total_tokens across all calls to get your monthly figure, then use the calculator below.

Your Cost Calculator

Enter your actual monthly token usage to see real savings

Quick Presets

Monthly Token Volume

30M tokens

Prompt / Completion Split

Prompt 70%Completion 30%

Claude Sonnet 5.5

$188.76/mo

$2,265.12/yr

$2.00/M input$10.00/M output

Cheaper

GPT-6.1 Terra

$66.00/mo

$792.00/yr

$1.00/M input$5.00/M output

Annual Savings

$1,473.12 saved per year

GPT-6.1 Terra cheaper · $122.76/mo

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