On the ACT, calculators are for Math only, you must bring your own permitted model, and the official list on act.org is the only source you should trust before test day. A calculator can help with messy arithmetic, but the policy details matter just as much as the buttons. Walk in knowing the rules so a useful tool does not turn into a check-in problem.
Math only, and bring your own
You may use a calculator on the Math test. Other ACT sections do not allow one. ACT does not hand you a calculator at the door, so pack a permitted model yourself. If you forget it, you still have to finish Math without one. That is stressful and avoidable.
Every Math problem can still be solved by hand. The calculator is optional help, not a requirement. Treat it as support for hard arithmetic and quick checks, not as something you must touch on every question. For packing the rest of your bag, see what to bring to the ACT.
Approved versus banned: keep the framing honest
ACT permits many graphing and scientific calculators. It also bans some models, including calculators with computer algebra systems (CAS), such as the TI-89. Exact model lists and exceptions can change, so do not rely on a friend's memory, an old prep book page, or a random forum post. Confirm your exact model against the current ACT calculator policy on act.org before you practice with it as your test-day device.
If you are choosing a first calculator, a common classroom graphing model that appears on the permitted side of the official list is often enough. Familiarity still matters more than features. Our hub on the best calculator for the ACT walks through that decision without turning the choice into a shopping contest.
No formula sheet connection
A calculator is not a substitute for knowing Math content. The ACT does not give you a formula sheet, and your calculator will not magically supply one either. You still need area and volume formulas, slope and distance, the quadratic formula, and basic trig ratios in your head. Use formulas to memorize for ACT Math as your content checklist, then use the calculator only when arithmetic or a quick graph check is the bottleneck.
Students who assume "the calculator knows it" often stall on setup questions. The device can evaluate an expression you enter. It cannot decide which expression belongs in the first place.
Batteries, backups, and calm check-in
Pack fresh batteries, and bring a spare set if your model uses replaceable ones. If you can, bring a second permitted calculator you also know how to use. A dead screen mid-section is a problem you can prevent the night before. Keep the device charged or powered the way the manufacturer recommends, and do a quick on/off check before you leave home.
Also plan for the boring logistics: put the calculator where you will not leave it in a locker or car, and make sure anyone helping you pack knows it is required only if you want one on Math. Sharing calculators during the test is not something you should count on. Bring your own.
Programs, memory, and other setup details
Some calculators can store programs, notes, or documents. Whether something must be cleared, disabled, or left alone is a policy detail that belongs on act.org, not in a guess from a blog post. Before test day, read the official calculator rules for your model family and follow them exactly. If you use a TI-84-style device, our TI-84 tips for the ACT focuses on useful Math workflows and points you back to the official policy for anything about memory or programs.
The safe habit is simple: practice with a clean, permitted setup that matches what you will be allowed to use, and do not invent workarounds the week of the test.
Desmos and other brand questions
Students often ask about Desmos hardware, Desmos apps, or phone-based calculators. Those are not the same thing. A phone or online app is a different category from a dedicated calculator device, and testing-room rules are strict about phones and similar devices. For a careful breakdown, see whether you can use Desmos on the ACT. The short version for this page: check act.org for which Desmos products, if any, are currently allowed, and do not assume a phone app is fine because the brand name sounds familiar.
Always confirm on act.org
This article is a practical overview, not a reprint of ACT's full policy. Rules can change. Before your test date, open the official calculator policy on act.org, confirm your model, and follow any setup instructions listed there. A two-minute check the week before is cheaper than a surprise at the door. Then get back to Math practice, including knowing when not to use your calculator even when it is allowed.
Start practicing
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This article offers general ACT prep guidance. The ACT can change from year to year, including its format, scoring, policies, test dates, and fees, so always confirm the latest details on the official ACT website at act.org before you make decisions. ACT® is a registered trademark of ACT, Inc. thirty-six is not affiliated with, endorsed by, or sponsored by ACT.