Most FRM candidates use the Texas Instruments BA II Plus, and it's on GARP's short list of permitted business calculators. The list includes the cheap, common models most finance candidates already own, and using anything else means your exam isn't graded.
Which calculator to buy is one of the first questions people ask, so here's the whole list and how I'd choose.
The full permitted list
Hewlett Packard:
- HP 12C
- HP 12C Platinum
- HP 12C Platinum 25th anniversary edition
- HP 12C 30th anniversary edition
- HP 12C Prestige
- HP 10B II
- HP 10BII+
- HP 20B
Texas Instruments:
- BA II Plus
- BA II Plus Professional
GARP says there are no exceptions. If you use a calculator that isn't on the list at any point during the exam, your exam won't be graded, so check your exact model and suffix against GARP's current policy before you sit.
What I'd buy
The BA II Plus is easy to use and well labeled, it handles the time value of money, cash flow (NPV and IRR), amortization and discount-factor work the FRM exam leans on, and it's inexpensive. It also works for the CFA, CFP, CAIA and CMA exams if you plan to stack credentials. If you don't have a strong preference, buy this one.
The HP 12C is the RPN classic: fast once you've mastered it, but with a learning curve, so pick it only if you already use RPN. The HP 10BII+ is an algebraic-entry alternative with solid financial and statistics functions at a low price, and the HP 20B is a capable business model. They're all permitted, so it comes down to which entry style and layout you prefer, and the exam doesn't reward a pricier model.
Whichever you buy, rehearse the quantitative keystrokes on real problems well before the exam. I built FreeFellow's FRM Part I and Part II question banks so candidates can drill that work, and both are free.
On exam day you can bring two units of the same permitted model as a backup. Bring fresh batteries too, since a calculator dying during a timed exam costs you time you can't get back.