Claude Code monthly cost estimator (AUD)

The estimator above projects your monthly Claude API bill in AUD based on a few key inputs. It assumes 50% prompt-cache hit rate, which is what we see in real Claude Code sessions with stable CLAUDE.md files.

Understanding the inputs

• Primary model: which model you’ll do most work on. Default to Sonnet; switch to Opus for tricky reasoning.
• Active sessions per day: how many distinct Claude Code conversations you start in a typical workday.
• Avg input tokens per session: includes CLAUDE.md + tool definitions + conversation history. Typical: 80k-150k.
• Avg output tokens per session: actual responses Claude generates. Typical: 5k-15k.
• Working days per month: most operators land at 22; adjust for your schedule.
• USD → AUD rate: defaults to 1.55, adjust to whatever your card converts at.

Reality check vs the calculator

Compare your real bill (from Anthropic Console → Usage) to what the calculator projects. If the real bill is much higher, the most likely causes:

1. You’re on Opus more than you realised. Switch the dropdown.
2. Your CLAUDE.md is huge. Audit it, anything over 4k tokens is paying tax on every turn.
3. You’re not caching. Cache hit rate drops to near zero if your CLAUDE.md changes mid-session or if you /clear constantly.
4. You’ve got long-running agentic loops. Set --max-turns caps.

If the real bill is much lower, congratulations, you’ve probably got better caching discipline than the average user.

What’s not modelled here

• MCP server tokens. Each tool call’s response counts toward output tokens. Heavy MCP use (lots of Xero queries) bumps the bill modestly.
• Web search. Counts as a tool call; doesn’t significantly affect token cost.
• Multi-modal. Image input is more expensive per “token-equivalent”, not modelled here.

For more on cost discipline, see Claude Code cost optimisation, five tactics that took our bill from $280 to $110 AUD/month.