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Found a ratio that looks off, a method that's missing, a fix that didn't work for your setup, or something on the site that's just broken? Send a message below, or email directly — either way reaches the same person and gets a real reply, not an automated one.

Corrections are especially welcome. If you have a specific reason to think a ratio range or a caffeine figure should move, say what and why in the message; changes to sourced numbers get checked against the reasoning on the methodology page before anything updates on the live site.

Questions about an order — the dial-in logbook or a contribution — are also welcome here, though for anything involving a charge itself, the receipt from Stripe will usually get you a faster answer than waiting on a reply. General coffee questions unrelated to a specific page are welcome too, though replies to those may take a little longer than a straightforward correction.

If you're reporting a broken tool or calculator, mentioning the browser and device you're using helps track it down faster — a phone-only display issue and a desktop JavaScript error look identical from the outside but need different fixes.

Replies come from a real person reading each message individually, which usually means a day or two rather than an instant auto-response — there isn't a support queue or a ticket system behind this, just someone reading what's sent and writing back directly, one message at a time, in the order they arrive.