Which is more cost-effective, GPT-5.6 Luna or GPT-4o Mini?

Based on 1M input + 1M output tokens, GPT-5.6 Luna costs $1.40/month versus GPT-4o Mini at $0.75/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 Luna scores 84 in coding and 85 in reasoning benchmarks. GPT-4o Mini scores 74 in coding and 78 in reasoning. See the full 5-category breakdown in the Benchmark Comparison section above.

What are the context window sizes of GPT-5.6 Luna and GPT-4o Mini?

GPT-5.6 Luna supports a 1.1M-token context window while GPT-4o Mini supports 128K 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 Luna has a speed score of 98/100 and GPT-4o Mini scores 97/100 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 Luna vs GPT-4o Mini

Model AOpenAI

GPT-5.6 Luna

Capability score (editorial)85/100

Cost / 1M Tokens: $0.50; 70% in · 30% out mix
Value Index (score÷cost): 170.0; Higher = better value

Speed: 98/100
Context: 1.1M
Tier: Fast Tier

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

Check the source

How we verify prices

Model BOpenAI

GPT-4o Mini

Capability score (editorial)78/100

Cost / 1M Tokens: $0.29; 70% in · 30% out mix
Value Index (score÷cost): 273.7; Higher = better value

Speed: 97/100
Context: 128K
Tier: Fast Tier

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

Check the source

How we verify prices

In-depth analysis

GPT-5.6 Luna vs GPT-4o Mini: Detailed Comparison

GPT-5.6 Luna is OpenAI's lightweight-tier language model with a 1.1M-token context window, excelling at data extraction. GPT-4o Mini from OpenAI is a lightweight-tier model supporting 128K tokens in context, with standout performance in data extraction.

This is a genuine tradeoff rather than a clear win. GPT-5.6 Luna leads by 17 points on combined coding and reasoning, and costs 43% more for the same text to do it. The margin is narrow enough that the answer depends on your workload: on tasks where the extra capability shows up, the premium pays for itself; on routine work it does not. GPT-5.6 Luna is priced at $0.20/M input tokens and $1.20/M output tokens. GPT-4o Mini costs $0.15/M input and $0.60/M output.

On iOPTERA's editorial scores, GPT-5.6 Luna leads with 84/100 for coding and 85/100 for reasoning, against GPT-4o Mini's 74/100 and 78/100.

Capability breakdown

Across the five core benchmark categories, here is how GPT-5.6 Luna and GPT-4o Mini stack up head to head:

coding

GPT-5.6 Luna leads

reasoning

GPT-5.6 Luna leads

data extraction

GPT-4o Mini leads

creative tasks

GPT-5.6 Luna leads

vision/multimodal

GPT-5.6 Luna leads

Best model by task

coding: GPT-5.6 Luna wins with 84/100
reasoning: GPT-5.6 Luna wins with 85/100
data extraction: GPT-4o Mini wins with 95/100
creative tasks: GPT-5.6 Luna wins with 84/100
vision/multimodal: GPT-5.6 Luna wins with 85/100

Estimated monthly cost at scale

For 10M + 2M tokens of text a month (counted the way OpenAI's tokenizer counts), GPT-5.6 Luna runs about $4.40 while GPT-4o Mini runs about $2.70 — GPT-4o Mini saves roughly $1.70 (39%) every month.

What actually decides it

Both models come from OpenAI, so they share a tokenizer, an API surface, and a billing account. Switching between them is a model-string change and nothing else — no new SDK, no re-tokenizing your prompts to re-estimate cost, no second vendor to onboard. That makes routing between them far cheaper to implement than a cross-vendor split.

These are the same lab's model at the same tier, 24 months apart — so this is an upgrade question, not a choice between alternatives. GPT-5.6 Luna is the current entry; GPT-4o Mini is here because plenty of production traffic still runs on it. If you are starting something new there is little reason to pick the older one, and if you are already on it the question is whether the migration cost is worth the gain.

The context gap is the largest single difference on this pair: GPT-5.6 Luna takes 1.1M tokens against 128K for GPT-4o Mini, roughly 8.2x. 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 — 98/100 versus 97/100. Neither model will feel noticeably quicker in an interactive product, so latency is not a reason to choose between them.

Neither model is the obvious answer. GPT-5.6 Luna leads on benchmarks, GPT-4o Mini on cost, and the gap is small on both. Run the calculator above with your real token mix — for most workloads that decides it faster than any benchmark table will.

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 Luna	GPT-4o Mini
List price (input / output)	$0.20 / $1.20	$0.15 / $0.60
Cached input	$0.0210% of the input price	$0.07550% of the input price
Batch API	50% off input and output	50% off input and output
Long prompts	Over 272K tokens: $0.40 / $1.80	—
Input with 80% cache hits	$0.056	$0.09

With 80% of input served from the cache, GPT-5.6 Luna costs 38% less than GPT-4o Mini for the same input text, counting each model's tokenizer.

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.

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

Capability scores

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

CategoryGPT-5.6 LunaGPT-4o MiniWinner

Coding

Reasoning

Extraction

Creative

Vision

GPT-5.6 Luna: 4 wins

GPT-4o Mini: 1 wins

GPT-5.6 Luna leads overall

Speed Score

98/100vs97/100

GPT-5.6GPT-4o

Context Window

1050Kvs128K

GPT-5.6GPT-4o

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 Luna: $0.08
GPT-4o Mini: $0.06

Business email

One typical email (~200 words)

~270 tokens

GPT-5.6 Luna: $5.40
GPT-4o Mini: $4.05

Code file

50-line Python script

~400 tokens

GPT-5.6 Luna: $8.00
GPT-4o Mini: $6.00

Prices shown are for 100,000 runs of each workload — one run costs a fraction of a cent on both GPT-5.6 Luna and GPT-4o Mini, 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%

GPT-5.6 Luna

$15.00/mo

$180.00/yr

$0.20/M input$1.20/M output

Cheaper

GPT-4o Mini

$8.55/mo

$102.60/yr

$0.15/M input$0.60/M output

Annual Savings

$77.40 saved per year

GPT-4o Mini cheaper · $6.45/mo

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