About

We help people buy used calculators without getting burned. Name the one you’re after, like an HP 12C for the CFA exam, a 15C, an HP-41CX with its modules, a 42S or a TI-59, and there’s a page for it. Each one tells you the model’s story, what it runs on, what it keeps in memory when it’s off, what wears out and what to check before you buy.

Some buyers want the calculator they used at work or school. Others want an RPN machine for the exam room or the bench, or a piece of HP history. What owners know about these calculators is scattered across old manuals, museum pages and forum threads, and a raw eBay search gives you none of it. So we keep 31 model pages in one place, write down the things that catch used buyers out (leaked batteries, dead display segments, keys that double-enter, a card reader that won’t pull a card, a reissue sold as an original) and pick the listings we’d buy.

We don’t sell calculators. No affiliate links. We earn nothing. We only recommend what we’d buy, and we’d rather you buy used. We run no analytics or tracking cookies, and we’re not affiliated with HP, Texas Instruments or any other calculator maker. See how we work for how the pages are researched and our disclosure for how links, picks and photos work.

Stack is part of allbutnew, a set of shops for secondhand gear. Got a calculator to sell? The “Get an offer” link on every model page sends it to our calculator expert, who replies by email.