Claude API vs OpenAI API: which should you use?

Both companies sell their AI two ways: as a chat app (ChatGPT, Claude) and as an API, which software uses to send work to the same models. If your team wants AI to do repeated work, such as categorizing tickets, coding invoice lines or sorting documents, the API is what you'll use. Choosing between Anthropic's and OpenAI's comes down to price, limits, data handling and where you're allowed to run it.

This guide compares the two side by side in plain English, then works out what categorizing 10,000 rows would cost on each.

• On price they're now close. Each has a small, cheap model and a mid-range model at the same list price, and both take half off for batch work. The real cost difference comes from how many tokens each model counts for your text and how much you send per request, not from the price list.
• On limits, plan ahead either way. Both start new accounts with a monthly spend cap that rises as you use the API and pay.
• On data, they're similar by default. Neither trains on API data by default, both keep requests for up to 30 days for abuse monitoring, and both offer zero data retention to approved customers.
• The biggest practical difference is where you can buy it. Claude is offered through Amazon Bedrock, Google Cloud and Microsoft Foundry as well as Anthropic directly. It's also offered as Claude Platform on AWS, billed through your AWS account. OpenAI's models are offered through Microsoft Foundry and, since 2026, Amazon Bedrock.
• On accuracy for your work, test both. It depends on your categories, and a test on your own rows settles it in an afternoon.

A token is roughly four characters of English. A short support ticket is about 100–200 tokens.

Things the list price doesn't show:

• Batch is half price on both. Use it when answers can wait hours, not seconds.
• Long prompts can cost more. Haiku 5.5 charges five times as much for prompts over 100,000 tokens, and GPT-6 models charge more for very long prompts. Sonnet 5.5 and Opus 5.5 keep the same price up to their 1 million token context. For categorizing rows, prompts are far below any of these.
• The same text can be a different number of tokens. Anthropic notes that Claude 4.7 and later count about 30% more tokens for the same text than earlier Claude models. Compare the cost of a real request, not just the price per token.
• Speed costs extra. Both sell faster processing: OpenAI's Fast mode is 2× the price, and Claude Opus 5.5 fast mode is $8 / $40.

A worked example, so the price lists mean something. Suppose each row is categorized by sending:

• the instructions, your category list and a short labeling guide: about 800 tokens;
• 10 similar past rows your team already decided, as examples: about 1,500 tokens;
• the row itself: about 200 tokens.

That's about 2,500 input tokens per question, with an answer budget of about 10 output tokens. Now ask each row three times and compare the answers, so you can tell the confident answers from the uncertain ones. That's 7,500 input tokens per row, or 75 million for 10,000 rows.

What changes the bill:

• The model size changes it the most: about 20 times between the small and mid models. Start with the small model, measure it, and move up only if it misses too much.
• Asking once instead of three times cuts it by two-thirds, but then you lose the easiest way to spot uncertain answers.
• Batch halves it, if the answers can wait.
• Caching cuts the repeated part (the instructions and categories), on both.

These are provider-only estimates from standard list prices and assumed prompt sizes. They exclude StayCharted subscription/add-on charges, taxes, retries and any extra reasoning/output tokens. Batch and cache savings depend on the integration; StayCharted currently sends standard requests, not batch jobs. Your own prompts and the tokenizer decide the real number, so measure a few hundred rows first.

This catches out more teams than price does. Both providers start a new account with low limits and raise them as you use and pay.

• Claude: new organizations may start in an Evaluation tier, below the standard limits. The standard tiers have monthly spend caps: $500 (Start), $1,000 (Build) and $200,000 (Scale). When you reach the cap, requests stop until the 1st of next month, unless you ask for a higher tier in the Console.
• OpenAI: the tier follows your total credit purchases: Build after $5 ($500 a month), Launch after $100 ($5,000 a month) and Grow after $500 ($200,000 a month).
• Per-minute limits apply on top of these. Claude counts requests and input and output tokens per minute for each model. OpenAI counts requests and tokens per minute and per day.

If a big file is due, raise your tier first, and send fewer requests at once if you start seeing rate-limit errors.

The two are closer than most people expect.

Through a cloud provider, the rules change. On Amazon Bedrock or Google Cloud, the cloud provider is the data processor, under your cloud agreement, and Anthropic's zero-retention option doesn't apply there. Claude Platform on AWS is different: it's billed and secured through your AWS account, but Anthropic runs it, under the Claude API's own retention rules.

Not legal advice: read your own agreement, or ask your security team which route they have approved.

Many companies can't sign up for a new API on a credit card, but already have a cloud agreement. The routes:

• Amazon Web Services:
  • Claude in Amazon Bedrock, run by AWS.
  • Claude Platform on AWS: Anthropic's own platform, billed on your AWS bill through AWS Marketplace, with IAM sign-in.
  • OpenAI models in Bedrock, announced in April 2026.
• Microsoft: OpenAI models and Claude in Microsoft Foundry.
• Google Cloud: Claude, alongside Gemini.

The models are the same; the price, the features available on the day of launch, and the terms can differ. Check the route your company already uses before signing up for a new account.

For categorizing your own data, nobody can tell you in advance, because it depends on your categories.

When we gave Claude Sonnet 5.5 only category names and a one-line definition each, it got 84.7% of 3,080 real banking support messages right. A model trained on the team's own examples got 93.7%. On medical abstracts, where the categories follow general knowledge, Claude did better than the trained model. The full benchmark →

We haven't run the same test on OpenAI's models, and a general benchmark won't tell you how either does on your queues and account codes. The reliable way is to give both models the same instructions and the same past examples, on the same rows your team already decided, and compare the results category by category.

• Your company already has an agreement with one: use that one. Approval usually takes longer than the setup.
• You run on AWS: Claude through Bedrock or Claude Platform on AWS keeps the bill and the access controls in AWS.
• You run on Microsoft: both are in Microsoft Foundry.
• High volume, simple categories: start with the small models (Claude Haiku 5.5 or GPT-6 Luna). They cost about a twentieth of the mid-range models.
• Long, messy text or a detailed labeling guide: try the mid-range models (Claude Sonnet 5.5 or GPT-6.1 Sol), and compare them on your rows.
• You need to fine-tune: neither is the right place now. Anthropic doesn't offer it for current Claude models, and OpenAI is winding it down. See Bedrock vs Foundry vs Vertex AI for classification.

StayCharted AI Model Trainer connects to both, so you don't have to pick from a spec sheet. In Workspace settings → AI platforms, paste an Anthropic key, an OpenAI key, or both. Amazon Bedrock, Microsoft Foundry and Google Cloud are also supported, with platform-specific connection settings. Bedrock uses an AWS role rather than a pasted API key. Claude Platform on AWS is a separate service and is not currently supported by StayCharted. Then:

1. Upload a spreadsheet of rows your team has already decided.
2. Set up Your AI Model on Claude, and another on OpenAI, from the same rows. Each question carries your categories, your labeling guide and the 10 most similar past rows, and each row is asked three times by default.
3. Each is tested on the same held-out rows, so the two reports compare like for like: accuracy per category, the categories it confuses, how often it kept its answer, and how many rows a review cutoff would send to a person.
4. Publish the one that does better. It fills files and Google Sheets and answers the API, with the uncertain answers going to a person in the Review Queue.

StayCharted sends each question as it's needed, at your provider's standard rate (not batch), on your account with them. How to use the OpenAI and Claude API without coding → · Compare plans →

• Use OpenAI or Claude without coding
• Compare five AI platforms for classification
• Your own AI or StayCharted models

• Anthropic:

  • Pricing (model prices, batch, caching, inference_geo 1.1×, the tokenizer note);
  • Rate limits (tiers, spend caps, cache-aware limits, batch limits);
  • Claude Platform on AWS;
  • Structured outputs;
  • Data retention and retention for covered models.

• OpenAI:

  • Pricing (GPT-6 prices, Batch and Flex 50%, Fast 2×, regional 10%);
  • Rate limits (usage tiers);
  • Your data (training, retention, zero data retention, regions);
  • Supervised fine-tuning (winding down).

• OpenAI on Amazon Bedrock: OpenAI on Amazon Bedrock.

• Benchmark: BANKING77 (Casanueva et al., 2020, CC BY 4.0) and Medical Abstracts (CC BY-SA 3.0), measured by StayCharted.

• OpenAI API quickstart

• Claude API quickstart

• Claude subscription API credits