Which is more cost-effective, GPT-5.6 Terra or Claude 3.5 Sonnet?

Based on 1M input + 1M output tokens, GPT-5.6 Terra costs $14.00/month versus Claude 3.5 Sonnet at $18.00/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?

GPT-5.6 Terra scores 93 in coding and 94 in reasoning benchmarks. Claude 3.5 Sonnet scores 88 in coding and 89 in reasoning. See the full 5-category breakdown in the Benchmark Comparison section above.

What are the context window sizes of GPT-5.6 Terra and Claude 3.5 Sonnet?

GPT-5.6 Terra supports a 1.1M-token context window while Claude 3.5 Sonnet supports 200K tokens. A larger context window lets you process more text in a single API call.

Which model is faster for real-time applications?

GPT-5.6 Terra has a speed score of 86/100 and Claude 3.5 Sonnet scores 95/100 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

GPT-5.6 Terra vs Claude 3.5 Sonnet

Model AOpenAI

GPT-5.6 Terra

Capability score (editorial)94/100

Cost / 1M Tokens: $5.00; 70% in · 30% out mix
Value Index (score÷cost): 18.8; Higher = better value

Speed: 86/100
Context: 1.1M
Tier: Smart Tier

List price from the OpenAI pricing page, verified October 12, 2026.

Check the source

How we verify prices

Model BAnthropic

Claude 3.5 Sonnet

Capability score (editorial)89/100

Cost / 1M Tokens: $6.60; 70% in · 30% out mix; ≈ $7.26 for the same text, tokenizer included
Value Index (score÷cost): 12.3; Higher = better value

Speed: 95/100
Context: 200K
Tier: Smart Tier

Last list price before the model was retired.

Its tokenizer produces about 10% 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.

How we verify prices

In-depth analysis

GPT-5.6 Terra vs Claude 3.5 Sonnet: Detailed Comparison

GPT-5.6 Terra is OpenAI's mid-range-tier language model with a 1.1M-token context window, excelling at reasoning. Claude 3.5 Sonnet from Anthropic is a mid-range-tier model supporting 200K tokens in context, with standout performance in creative tasks.

GPT-5.6 Terra is both the cheaper and the stronger model here — for the same text it costs 31% less than Claude 3.5 Sonnet and still leads on combined coding and reasoning by 10 points. There is no tradeoff to weigh on this pair: unless you need something specific from Claude 3.5 Sonnet, the cheaper model is simply the better one. GPT-5.6 Terra is priced at $2.00/M input tokens and $12.00/M output tokens. Claude 3.5 Sonnet costs $3.00/M input and $15.00/M output.

Claude 3.5 Sonnet turns the same text into about 10% more tokens than GPT-5.6 Terra, because their tokenizers differ — so comparing list prices per token understates what Claude 3.5 Sonnet costs. For the same text, split 70% input and 30% output and counted the way OpenAI's tokenizer counts it, Claude 3.5 Sonnet works out at about $7.26 per million tokens and GPT-5.6 Terra at $5.00. Every cost figure on this page includes that difference.

On iOPTERA's editorial scores, GPT-5.6 Terra leads with 93/100 for coding and 94/100 for reasoning, against Claude 3.5 Sonnet's 88/100 and 89/100.

Capability breakdown

Across the five core benchmark categories, here is how GPT-5.6 Terra and Claude 3.5 Sonnet stack up head to head:

coding

GPT-5.6 Terra leads

reasoning

GPT-5.6 Terra leads

data extraction

GPT-5.6 Terra leads

creative tasks

GPT-5.6 Terra leads

vision/multimodal

GPT-5.6 Terra leads

Best model by task

coding: GPT-5.6 Terra wins with 93/100
reasoning: GPT-5.6 Terra wins with 94/100
data extraction: GPT-5.6 Terra wins with 93/100
creative tasks: GPT-5.6 Terra wins with 92/100
vision/multimodal: GPT-5.6 Terra wins with 93/100

Estimated monthly cost at scale

For 10M + 2M tokens of text a month (counted the way OpenAI's tokenizer counts), GPT-5.6 Terra runs about $44.00 while Claude 3.5 Sonnet runs about $66.00 — GPT-5.6 Terra saves roughly $22.00 (33%) every month.

What actually decides it

GPT-5.6 Terra and Claude 3.5 Sonnet 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-5.6 Terra and Claude 3.5 Sonnet are 25 months apart, which is more than one generation in this market. Benchmark comparisons across that gap flatter the older model: it was measured against the evaluations that existed at the time. Treat Claude 3.5 Sonnet's scores as a floor for what it does well and be sceptical of a close-looking result.

The context gap is the largest single difference on this pair: GPT-5.6 Terra takes 1.1M tokens against 200K for Claude 3.5 Sonnet, roughly 5.3x. That is the difference between feeding in a whole repository or a full contract set and having to chunk it. If your work involves documents you cannot split cleanly, this decides it on its own.

Throughput is close enough to ignore — 95/100 versus 86/100. Neither model will feel noticeably quicker in an interactive product, so latency is not a reason to choose between them.

GPT-5.6 Terra wins this comparison outright — cheaper and stronger. Choose Claude 3.5 Sonnet only if it has a specific capability you need; on price and benchmarks it is behind on both.

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	GPT-5.6 Terra	Claude 3.5 Sonnet
List price (input / output)	$2.00 / $12.00	$3.00 / $15.00
Cached input	$0.2010% of the input price	—
Batch API	50% off input and output	—
Long prompts	Over 272K tokens: $4.00 / $18.00	—
Input with 80% cache hits	$0.56	—

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 OpenAI, Anthropic.

Capability scores

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

CategoryGPT-5.6 TerraClaude 3.5Winner

Coding

Reasoning

Extraction

Creative

Vision

GPT-5.6 Terra: 5 wins

Claude 3.5 Sonnet: 0 wins

GPT-5.6 Terra leads overall

Speed Score

86/100vs95/100

GPT-5.6Claude

Context Window

1050Kvs200K

GPT-5.6Claude

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

GPT-5.6 Terra: $0.80
Claude 3.5 Sonnet: $1.32

Business email

One typical email (~200 words)

~270 tokens

GPT-5.6 Terra: $54.00
Claude 3.5 Sonnet: $89.10

Code file

50-line Python script

~400 tokens

GPT-5.6 Terra: $80.00
Claude 3.5 Sonnet: $132.00

Prices shown are for 100,000 runs of each workload — one run costs a fraction of a cent on both GPT-5.6 Terra and Claude 3.5 Sonnet, 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%

Cheaper

GPT-5.6 Terra

$150.00/mo

$1,800.00/yr

$2.00/M input$12.00/M output

Claude 3.5 Sonnet

$217.80/mo

$2,613.60/yr

$3.00/M input$15.00/M output

Annual Savings

$813.60 saved per year

GPT-5.6 Terra cheaper · $67.80/mo

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