How big is the GPT-5.5 Pro context window?

GPT-5.5 Pro has a 1,050,000-token context window, more than 2.5x the 400K window of GPT-5 Pro and 5x the 200K window of o1-pro.

How much does 1M input and 250K output tokens per month cost on GPT-5.5 Pro?

$75 per month at standard rates: $30 for the input tokens plus $45 for the 250K output tokens. The same volume on the batch API costs $37.50.

GPT-5.5 Pro Pricing — API Cost Breakdown

Q: Is GPT-5.5 Pro cheaper than o1-pro?

Yes. o1-pro costs $150/$600 per 1M tokens, five times GPT-5.5 Pro's $30/$180, with only a 200K context window. For most reasoning workloads GPT-5.5 Pro is the better deal on both price and context.

GPT-5.5 Pro costs $30 per 1M input tokens and $180 per 1M output tokens. The context window holds 1,050,000 tokens, and OpenAI sells a batch variant at $15/$90 for workloads that can wait a few hours. All figures below come from live OpenRouter listing data (434 models, checked September 2026).

Pricing overview

Metric	Value
Input price (per 1M tokens)	$30
Output price (per 1M tokens)	$180
Batch input / output	$15 / $90
Context window	1,050,000 tokens
Provider	OpenAI

Output tokens drive the bill here. At a typical 4:1 input-to-output ratio, output costs are about six times the input spend, so prompts that generate long answers will hurt more than long prompts. The $180 output rate is the highest OpenAI currently lists outside the retired o1-pro.

GPT-5.5 Pro vs other flagship reasoning models

Model	Input (per 1M)	Output (per 1M)	Context
GPT-5.5 Pro	$30	$180	1.05M
GPT-5.4 Pro	$30	$180	1.05M
GPT-5 Pro	$15	$120	400K
o1-pro	$150	$600	200K
Claude Opus 4.1	$15	$75	200K

GPT-5.4 Pro lists at the exact same rates and context size, so the two are interchangeable on price alone. GPT-5 Pro is half the price but caps out at 400K tokens. o1-pro costs five times as much for a fifth of the context, which is why it shows up mostly in legacy pipelines now. Claude Opus 4.1 undercuts GPT-5.5 Pro on both rates, though its 200K window can't hold the million-token documents GPT-5.5 Pro swallows in one pass.

Costs at scale

Same workload every time: 1M input tokens plus 250K output tokens per month.

Model	Input cost	Output cost	Monthly total
GPT-5.5 Pro	$30	$45	$75
GPT-5.4 Pro	$30	$45	$75
GPT-5 Pro	$15	$30	$45
o1-pro	$150	$150	$300
Claude Opus 4.1	$15	$18.75	$33.75
GPT-5.5 Pro (batch)	$15	$22.50	$37.50

Scale the workload up tenfold and the gaps get uncomfortable: 10M in and 2.5M out per month runs $750 on GPT-5.5 Pro standard, $375 on batch, and $3,000 on o1-pro.

Batch discount math

The batch API pays half price on both directions. Input drops from $30 to $15, output from $180 to $90. No minimum volume, no tiered schedule, just 50% across the board.

Token volume (per month)	Standard cost	Batch cost	Saved
1M in / 250K out	$75.00	$37.50	$37.50
5M in / 1M out	$330.00	$165.00	$165.00
10M in / 2.5M out	$750.00	$375.00	$375.00

The catch is latency. Batch requests complete within 24 hours, so this only works for overnight backfills, report generation, evaluation runs, and anything else that isn't user-facing. For interactive traffic you pay full price.

When GPT-5.5 Pro is worth it

You need to reason over documents longer than 400K tokens. Nothing else in OpenAI's current lineup holds a million tokens, and re-chunking a huge doc into a cheaper model usually costs more than the premium.
The task genuinely needs deep reasoning and the answer is expensive to get wrong. A single wrong legal analysis or code migration costs more than a year of the price gap versus GPT-5 Pro.
Your volume is low enough that the $75/month benchmark number above reads as rounding error in your budget.

And when it isn't. If your workload fits in 400K tokens and doesn't need the extra reasoning depth, GPT-5 Pro does the same job for 40% less. If it fits in 200K and quality requirements are moderate, Claude Opus 4.1 is the cheapest flagship on the board. If you're doing bulk non-urgent processing, run GPT-5.5 Pro through the batch API and cut the bill in half without switching models.

Estimate your own bill

Plug your token counts into the OpenRouter pricing calculator to see GPT-5.5 Pro against every other listed model for your actual workload, not a generic benchmark.

Common questions

How much does GPT-5.5 Pro cost?

$30 per 1M input tokens, $180 per 1M output tokens on the standard API. The batch variant is $15/$90.

How big is the context window?

1,050,000 tokens. That's more than double GPT-5 Pro's 400K and five times o1-pro's 200K.

Is GPT-5.5 Pro cheaper than o1-pro?

Yes, by a wide margin. o1-pro lists at $150/$600, five times the standard rates, with a fifth of the context. Unless you're locked into o1-pro for a legacy reason, GPT-5.5 Pro wins on price and window size.

What does 1M input and 250K output per month cost?

$75 on the standard API. Run the same volume through batch and it's $37.50.