Understanding OpenRouter's Transaction Fees and Cost Structure

OpenRouter is a convenient service that allows you to access LLMs from OpenAI, Google, Anthropic, and others through a single API endpoint. It frees you from managing API keys for each model, dramatically improving development efficiency.

However, there are points that are surprisingly easy to overlook regarding its pricing structure, especially the Transaction Fees. Based on information as of November 2025, this article summarizes our investigation into OpenRouter’s fee structure and key points for accurately understanding your costs.

Conclusion: When Do OpenRouter Fees Apply?

To get straight to the point, OpenRouter’s main fees are incurred only once when purchasing credits. Fees are not added on top of each API call.

Point: OpenRouter does not add any markup to the model usage fees themselves. The official prices set by the providers are applied as-is.

OpenRouter’s Basic Pricing Structure

First, as a fundamental point, OpenRouter is not a subscription (monthly flat-rate) service, but operates on a prepaid credit + pay-as-you-go model.

Purchase Credits: Charge credits to your account in advance in USD (e.g., $10).
Use the API: Call the API with the model you want to use.
Costs are Deducted: Fees based on the number of tokens used by the model are deducted from your charged credit balance.

Three Cases Where Fees Apply

The timing and content of fee charges mainly fall into the following three cases.

1. Payment Processing Fees When Purchasing Credits

This is the most significant fee. Payment processing fees are incurred when charging credits to your account.

Payment Method	Fee
Credit Card/PayPal, etc.	5.5% (with a minimum fee of $0.80)
Cryptocurrency (USDC, etc.)	5%

Rather than frequently charging small amounts, charging larger amounts at once is more cost-effective as it reduces the impact of the minimum fee.

2. Fees When Using BYOK (Bring-Your-Own-Key)

When using “BYOK” mode, where you register your own provider API key (e.g., your OpenAI API key) with OpenRouter, additional fees may apply.

Up to 1 million requests per month: Free
After exceeding 1 million requests: An additional 5% fee is charged on the base cost of the model.

This fee is also deducted from your OpenRouter credit balance. If you use a regular OpenRouter API key, this fee does not apply.

3. Using Free Models

OpenRouter also offers free models tagged with free. While these are basically free to use, they have daily request limits and other restrictions, so caution is needed for production environments.

Concrete Cost Calculation Example

Let’s consider a scenario to see how much it actually costs.

Scenario: Using a paid model (input: $0.50/M tokens, output: $2.50/M tokens) to process a total of 100,000 input tokens and 50,000 output tokens.

Step 1: Calculating Model Usage Fees

Input Cost: 100,000 tokens = 0.1M tokens × $0.50 = $0.05
Output Cost: 50,000 tokens = 0.05M tokens × $2.50 = $0.125
Total Model Usage Fee: $0.05 + $0.125 = $0.175

This $0.175 will be deducted from your credit balance.

Step 2: Considering Credit Purchase Fees

If you had purchased $10 in credits via credit card for this usage, the total payment would be as follows:

Credit Amount: $10.00
Fee: $10.00 × 5.5% = $0.55 → Since the minimum fee of $0.80 applies, $0.80
Total Payment: $10.00 + $0.80 = $10.80

With this $10.80 payment, $10.00 worth of credits will be charged to your account. It’s important to note that this fee is not additionally charged with each API call.

Summary: Points to Keep in Mind for Cost Management

OpenRouter’s fees are simple, but for accurate budget planning, keep the following points in mind:

Fees are incurred when purchasing credits: Think of them as a fixed rate at the time of credit charging, not as variable costs per API usage.
Be aware of actual costs: Plan your budget with total costs in mind, including payment processing fees (5.5%, etc.), not just the model’s per-token price.
Charge in bulk: Charging small amounts multiple times may become more expensive due to the minimum fee ($0.80).

OpenRouter is a cost-effective service when considering its convenience. Understand the fee structure correctly and use it wisely.

That’s all about OpenRouter’s transaction fees, from the Gemba.