The problem
Both Claude and ChatGPT meter your usage, and neither shows the number where you are working. The figure exists — Claude reports it on a settings page — but checking it means leaving your conversation, and by then you are already guessing at how much room is left.
What makes this harder than it looks is that the whole conversation is re-sent to the model on every single turn. A chat that feels short on screen can be consuming several times what you would estimate from the words in front of you. That mismatch is the single most common reason people are surprised by a usage limit.
What Token Counter does
It is a Chrome extension that puts the numbers in the conversation itself. Three of them:
- Draft — prices what you are typing, live, before you send it.
- Chat — the running total for the whole conversation.
- Overhead — on Claude, the system prompt, the features you have switched on, and your saved memory. ChatGPT does not expose this to the browser, so no figure is shown there.
Alongside those, it shows the usage limits for your plan and when each one resets — on both claude.ai and chatgpt.com.
The tokenizer on this site
The tokenizer here runs the same engine as the extension, so you can paste any text and get a count without installing anything. It is genuinely useful on its own if you just want to know how large a document is before you hand it to a model.
How accurate it is
The engine is the open-source gpt-tokenizer library using the o200k_base encoding — the same family ChatGPT uses. Claude splits text a little differently, so Claude figures are close estimates. For exact Claude numbers, Anthropic publishes an official token counting API.
The extension marks every figure it shows with a — Draft, Chat and Overhead alike, on both sites. That is not a Claude-only marker — each number is an estimate for a specific reason. The tokenizer is GPT-family rather than Claude’s own. The system prompt is added as a fixed constant rather than read from the model. Images and documents are sized by formula — image patches, and a flat figure per page — rather than counted exactly. And on ChatGPT, non-text parts of a message are skipped entirely. Read the numbers as close, not exact.
A rule of thumb people ask for constantly: about 110 tokens per 100 words of ordinary English prose. But that number moves a lot with the kind of text — technical prose and long identifiers run higher, roughly 150 to 200 per 100 words, and number-heavy text can reach 250. Those come from a handful of samples rather than a corpus, so read them as direction, not precision. When the number matters, tokenize the actual string.
How it is built
Everything runs on your device. The extension ships its own copy of the tokenizer and talks only to the two sites you are already signed in to — with one exception the privacy policy spells out: on first install it opens a single tab to this site’s welcome page. Nothing you type is collected, transmitted, or stored anywhere we can see it — there is no backend and no account to create. The privacy policy covers this in full, including the exact Chrome permissions the extension requests.
Who it is for
Developers pasting long files into a model, writers in all-day sessions, analysts working through large documents, and anyone on a paid plan who would rather pace their usage than discover the ceiling by hitting it.
Contact
Questions, bugs, or feedback: [email protected].