Interactive LLM Cost Calculator
Want to calculate your exact parameters and operational expenses? Run the calculations locally inside your browser.
Launch LLM Cost Calculator1. Step 1: Model Your Average Query Profile
Calculate the average length of your input prompts (including system instructions and RAG documents) and expected model responses in characters. Convert these values to tokens by dividing English words by 0.75, or code characters by 2. This defines your baseline token profile.
2. Step 2: Factor in User Interaction Volatility
Do not assume users only submit one query. Model your daily active users (DAU) and their average messages per session. If 1,000 users send an average of 5 messages daily, you process 5,000 queries per day. Multiply this by your query token profile to find daily token volumes.
3. Step 3: Inject an Execution Safety Margin
In production, things go wrong. Users submit massive copy-pasted documents, system prompts fail and loop, and retry middleware duplicates calls. Always add a 25% safety margin to your final cost estimates to avoid exceeding developer budgets.
Frequently Asked Questions
How do I prevent runaway API billing?
Set hard spending limits inside your OpenAI and Anthropic dashboards. If your application exceeds the budget, the API keys temporarily disable, preventing unexpected credit card charges.
Should I calculate cost per user?
Yes. Calculating cost-per-user helps you determine subscription prices or token usage quotas for your customers to maintain healthy operating margins.