The power button turns the calculator on and off, and on some models it also clears the display
The power button on a scientific calculator is usually labeled ON, PWR, or sometimes ON/C (on/clear). Pressing it once wakes the calculator from sleep mode or turns it on completely if it was off. Pressing it again shuts it down. On calculators where the button says ON/C, a single press turns the device on, and a longer press — usually two to three seconds — clears everything from the display and memory.
Most scientific calculators run on either batteries or solar power, or both. The power button does not drain the battery significantly when the calculator is off, because the device enters a true sleep state rather than staying partially active. If your calculator has not been used in weeks or months, pressing the power button should bring it back to life when ready.
Key Takeaways
- A single press of the power button turns the calculator on; a second press turns it off.
- On models labeled ON/C, holding the button for two to three seconds clears the display and stored values.
- Turning the calculator off does not erase stored numbers or programmed functions — those remain in memory.
- Solar-powered calculators may not respond to the power button in very dim light, because they have no battery to fall back on.
How the ON/C button differs from a regular clear button
Many scientific calculators have both a power button and a separate C or AC (all clear) button. The difference matters. A single press of C clears only the current calculation — the number you just typed and any operation you started. A press of AC clears the display and any stored values, but leaves the calculator running. The ON/C button, by contrast, is dual-purpose: a short press clears the display, and a long press (usually held for two to three seconds) powers the device off entirely.
If your calculator has a separate power button and a separate clear button, use the clear button for everyday work. Reserve the power button for when you are done using the calculator and want to save battery life. This is especially important for battery-powered models, because turning off the calculator between uses can extend battery life by months or even years.
Why some scientific calculators have no visible power button
Older or very basic scientific calculators sometimes lack a dedicated power button altogether. These models stay on as long as they have power, and they turn off only when the battery dies or is removed. Some newer models use an auto-off feature instead: the calculator powers down automatically after 10 to 15 minutes of inactivity. This design saves battery life without requiring you to remember to turn the device off.
If your calculator has auto-off and you want to keep it on while you work, you may need to press any button every few minutes to reset the timer. Check your calculator's manual or the back of the device for the auto-off interval — it varies by model. Some calculators let you disable auto-off in the settings menu, though this will drain the battery faster.
Solar-powered calculators and the power button
A scientific calculator with both solar cells and a battery will use the power button normally in any lighting condition. However, a calculator with only solar power has no battery to fall back on. In very dim light — such as indoors at night or in a dark room — the solar cells cannot generate enough power to respond to the power button. The calculator straightforward will not turn on until it receives adequate light.
If you own a solar-only calculator and find that the power button does not work, move the device to a brighter location and try again. This is not a malfunction; it is how solar-only calculators are designed. For reliable use in any lighting, choose a model with both solar and battery power, or battery power alone.
What happens to your stored numbers when you turn the calculator off
Turning off a scientific calculator does not erase any numbers or functions you have stored in its memory. When you press the power button to turn it back on, any values you saved using the M+, M−, or STO (store) buttons will still be there. The display will be blank, but the memory is intact. This is true for both battery-powered and solar-powered models.
The only way to erase stored values is to press the AC (all clear) or ON/C button while the calculator is on. Some calculators also have a CLR or RESET button that clears memory specifically, separate from the display. Check your manual if you need to wipe all stored data before handing the calculator to someone else or putting it away for a long time.
Troubleshooting when the power button does not work
If pressing the power button does nothing, the most common cause is a dead or missing battery. Open the battery compartment — usually on the back of the calculator — and check that the battery is installed correctly, with the positive side facing up. If the battery looks old or corroded, replace it with a fresh one of the same type. The battery compartment usually requires a small screwdriver to open.
If the battery is new and correctly installed but the power button still does not respond, try pressing it firmly for a full three seconds. Some calculators require a longer press than others. If the calculator still does not turn on after that, the power button itself may be stuck or broken. At that point, the calculator will likely need repair or replacement, depending on its age and cost.
Frequently Asked Questions
Does turning off my calculator erase my calculations?
No. Turning off the calculator clears the display but leaves any numbers you stored in memory intact. When you turn it back on, those stored values will still be there. Only pressing the clear button erases calculations.
Why does my solar calculator not turn on in the dark?
If your calculator has only solar power and no battery, it cannot generate electricity in dim light. Move it to a brighter location. If it has both solar and battery power, the battery should work in any lighting condition — check that the battery is installed and not dead.
Is it bad to leave my calculator on all the time?
Leaving a battery-powered calculator on drains the battery faster than turning it off between uses. Turning it off when you are done can extend battery life by months. Solar calculators with a battery will use the battery in dim light, so turning them off also helps preserve power.
What does the ON/C button do if I hold it down?
Holding the ON/C button for two to three seconds powers the calculator off and clears the display. A single short press just turns it on or clears the current entry, depending on whether the calculator is already running.
Can I replace the battery myself?
Yes. Most scientific calculators use standard batteries like AA, AAA, or button cells. Open the battery compartment on the back with a small screwdriver, note which way the old battery faces, and install the new one the same way. If you are unsure of the battery type, check the manual or the inside of the battery compartment.