The reset process depends on your Casio model, but most use a small reset button or a key combination

Casio calculators don't all reset the same way. Some models have a physical reset button on the back or side; others use a key sequence you press while the calculator is on. A few require you to remove the battery. The method that works for your calculator depends on whether it's a basic four-function model, a scientific calculator, or a graphing calculator like the fx-9750GII or ClassPad series.

Before you reset, understand what happens: the calculator returns to factory defaults, which means all stored data, custom settings, and any programs you've entered will be erased. The memory clears completely. If you've saved important calculations or custom functions, write them down first.

Key Takeaways

  • Most Casio scientific and graphing calculators have a reset button labeled RESET on the back or side panel that you press with a pen or paperclip.
  • Some models require you to hold specific keys (often SHIFT and 9, or SHIFT and DEL) while turning the calculator on to access a reset menu.
  • Basic four-function Casio calculators often reset by removing the battery for 30 seconds, then reinserting it.
  • Resetting erases all stored data, programs, and custom settings permanently, so note down anything you need before you start.
  • If your calculator won't respond to any reset method, a dead battery or internal hardware failure may be the cause rather than a software problem.

Reset button method for scientific and graphing models

Most Casio scientific calculators (like the fx-991EX or fx-115ES) and graphing calculators have a small RESET button recessed into the back or side of the case. You can't press it with your finger—you need a straightened paperclip, a ballpoint pen, or a thin pushpin. Look for a small hole labeled RESET, usually near the battery compartment or on the upper back edge.

Insert the tool into the hole and press firmly until you feel it click. Hold it for about one second. The display will go blank for a moment, then show the startup screen. The calculator is now reset to factory settings. All data is gone, and the calculator will behave as though it just came from the box.

If you can't find a RESET button on your model, check the manual or the Casio website for your specific calculator number (printed on the front or back). Some older or regional variants may use a different reset method.

Key combination reset for models without a physical button

Calculators like the Casio fx-CG50 or some ClassPad models don't have a physical reset button. Instead, you use a key combination while powering on. The most common sequence is SHIFT + 9 (or sometimes SHIFT + DEL), held down while you press the ON button. Keep holding the keys for two to three seconds after the calculator powers on.

A menu will appear asking you to confirm the reset. Select YES or OK using the arrow keys and the equals button. The calculator will restart and return to factory defaults. The exact key combination varies by model, so if SHIFT + 9 doesn't work, try SHIFT + DEL or consult your manual.

Some graphing models show a "Mem Clear" or "Initialize" option in the main menu under SETUP or SYSTEM. You can also reset from there without using key combinations, though this method is slower and requires navigating menus.

Battery removal reset for basic calculators

Older Casio four-function or basic scientific calculators sometimes reset by removing the battery. Open the battery compartment on the back (usually held by a small screw or a sliding latch), and take out the battery. Wait at least 30 seconds—this clears the calculator's internal memory. Then reinsert the battery and close the compartment.

When you turn the calculator on, it will display the startup screen and all stored data will be gone. This method works because the calculator's memory is powered by the battery, and removing it cuts power to the memory circuits completely.

If your calculator uses a solar panel plus battery (common in Casio models), covering the solar panel with your hand while the battery is out speeds up the memory clear. Some calculators also have a small capacitor that holds a charge for a few seconds after battery removal, so waiting the full 30 seconds ensures it fully drains.

What to do if the reset doesn't work

If you've tried the reset method for your model and the calculator still won't respond or shows an error, the problem may not be software. A stuck key, a dead battery, or internal hardware damage can prevent a reset from working or make the calculator unresponsive even after reset.

Try replacing the battery with a fresh one first—a weak battery can cause the calculator to behave erratically and may prevent reset functions from working. If the calculator still doesn't respond after a battery change, the reset button or key combination may be broken, or the internal memory circuit may have failed.

At that point, the calculator likely needs repair or replacement. Casio offers repair services through their website, though the cost may exceed the price of a new calculator depending on the model.

When you should reset your calculator

Reset your Casio when it's frozen and won't respond to key presses, when you want to clear all stored data before selling or giving it away, or when you've accidentally changed settings and can't find your way back to defaults. You might also reset if a program you entered is causing errors and you can't delete it normally.

Don't reset just because the calculator is slow or the display looks dim—those are usually battery issues, not software problems. A reset won't fix a dim display or sluggish response if the battery is low. Replace the battery first and see if that solves the problem.

Frequently Asked Questions

Will resetting my calculator erase the programs I wrote?

Yes. A reset erases all stored data, custom programs, and user-defined functions. The calculator returns to the exact state it was in when it left the factory. If you need to keep a program, photograph it or write it down before you reset.

What if I press the reset button and nothing happens?

Make sure you're using a thin tool like a paperclip or pen tip, not your finger. Press firmly and hold for one to two seconds. If the calculator still doesn't reset, the button may be stuck or broken, or the battery may be dead. Try replacing the battery and trying again.

Can I reset my Casio graphing calculator without losing my programs?

No. A full factory reset erases everything. Some graphing calculators let you clear only the main memory while keeping the program area, but this is not a true reset. Check your manual for a "Clear Memory" option that may preserve programs, though this varies by model.

How long does a reset take?

A reset takes a few seconds. The display will go blank briefly, then show the startup screen. You'll be back to using the calculator within 10 seconds of pressing the reset button or key combination.

Do I need to reset my calculator if the battery dies?

No. When you replace the battery, the calculator will power back on normally. You only need to reset if you want to erase data or if the calculator is frozen and won't respond to key presses.