# Simon Willison: Claude Token Counter with Model Comparisons — Opus 4.7 Tokenizer Costs ~40% More

> Opus 4.7's new tokenizer produces 1.46x more text tokens than 4.6 — same price per token, but effectively ~40% more spend per prompt.

- Org: Simon Willison
- Date: 2026-04-20
- Category: article, tool
- Source: https://simonwillison.net/2026/Apr/20/claude-token-counts/
- Canonical page: https://ai-tldr.dev/releases/simonw-claude-token-counter/

## In short

Simon Willison upgrades his Claude token counter to compare models side-by-side and finds Opus 4.7's new tokenizer uses 1.46x more text tokens than Opus 4.6 — identical per-token pricing, so ~40% more spend per typical prompt.

## What it is

A blog post and tool update from Simon Willison, published April 20, 2026. Willison extended his Claude Token Counter web app to show token counts for multiple Claude models side-by-side, then ran real prompts through it and surfaced a practical pricing implication: Opus 4.7's new tokenizer produces significantly more tokens from the same text than Opus 4.6.

## How it works

The upgraded tool calls Anthropic's token counting API against each model in parallel and shows the results side-by-side. The key measurement: the same system prompt consumed 1.46x more tokens on Opus 4.7 than 4.6 — above Anthropic's own stated 1.0–1.35x range for the tokenizer change. A high-resolution PNG showed a 3.01x ratio, but this was entirely due to Opus 4.7's new ability to process images at up to 2,576 pixels (not pure tokenization overhead). PDFs showed a moderate 1.08x delta.

## Why it matters

Anthropic held Opus 4.7 pricing flat at $5/M input tokens, so the new tokenizer is an effective hidden cost increase for text workloads: expect roughly 40% more input spend when migrating from Opus 4.6. The tool is now a practical pre-migration audit — paste your actual system prompt and see the token delta before committing.

## Who it's for

Teams budgeting API costs for a migration from Claude Opus 4.6 to Opus 4.7.

## Try it

https://tools.simonwillison.net/claude-token-counter

## Links

- [Blog Post](https://simonwillison.net/2026/Apr/20/claude-token-counts/)
- [Token Counter Tool](https://tools.simonwillison.net/claude-token-counter)