AI cost calculator: BYOK vs subscriptions.

How the calculator works

The estimates use these per-minute averages, derived from real conversation logs across founder workflows:

• Input tokens per minute: ~4,000 (you typing, plus the AI re-reading prior context)
• Output tokens per minute: ~1,600 (the AI's response stream)
• Working days per month: 22

Pricing is per the providers' published rates as of early 2026. Numbers are approximate; your actual usage will vary based on conversation length, context window size, and model behavior.

Why BYOK usually wins

Subscription tools charge a flat $20/month regardless of usage. Most founders have lumpy AI usage: $0 some weeks, heavy others. BYOK matches the lumpiness. You pay for what you actually use.

For light users (under 30 minutes daily), BYOK with Claude Sonnet or Gemini Flash typically runs $3-12/month. For heavy users (over 2 hours daily on Claude Sonnet), BYOK can hit $40-60/month, which is more than a single subscription but typically still less than the stack of subscriptions most founders pay for.

What's not in the model

• API credits sometimes included in subscriptions (e.g., the small free tier OpenAI bundles with ChatGPT Plus)
• Volume discounts for very high usage (which generally don't apply at indie scale)
• Cost of Cursor / Continue.dev / similar for code work (which is its own bucket)
• Variable token usage based on context window (longer conversations = more tokens per turn)

How to set a hard spending cap

All three providers (Anthropic, OpenAI, Google) let you set a hard monthly cap so you can't accidentally exceed your budget. Set it to 2x your estimated monthly usage as a safety margin.

• Anthropic: Console → Plans & Billing → Spending limit
• OpenAI: Settings → Limits → Hard limit
• Google: Cloud Console → Billing → Budgets

The full setup guide is at /api-key-setup-guide.