You can change most Casio watch batteries at home with a small screwdriver and a few minutes
Most Casio watches use a standard battery that you can replace without tools beyond a small Phillips or flathead screwdriver. The process is straightforward: open the case back, note which battery is inside, buy a replacement of the same type, swap it out, and close the case. You do not need to send the watch to a jeweler or service center unless the case back is glued shut or the watch is water-resistant above a certain depth.
The time investment is usually under five minutes once you have the right battery in hand. The cost of the battery itself ranges from two to eight dollars, depending on the type. The main risk is dropping a small screw or battery, so work over a clean, flat surface with good light.
Key Takeaways
- Most Casio watch case backs are held by one to four small screws that you can remove with a Phillips or flathead screwdriver.
- The battery type is printed on the old battery itself — common types include SR626SW, LR626, and CR2032 — and you should buy an exact replacement.
- Water-resistant watches rated below 30 meters (100 feet) are usually safe to open at home; anything deeper may require a jeweler to reseal the case.
- After inserting the new battery, test the watch before closing the case back to confirm it powers on.
What you need to open the case back
Gather a small Phillips screwdriver, a flathead screwdriver, and a clean, well-lit work surface before you start. Most Casio watches use Phillips screws, but some digital models use flathead. If you do not have both, a jeweler's screwdriver set costs five to ten dollars and includes multiple sizes.
You will also need the correct replacement battery. Do not guess the type — open the case back first, look at the old battery, and write down the code printed on it. That code (like SR626SW or LR626) is what you search for when you buy the replacement. Battery retailers like Batteries Plus, Walgreens, and Amazon all stock common Casio types, and the battery usually arrives within a day or two if you order online.
How to remove the case back
Locate the small screws around the edge of the case back — the metal or plastic disc on the back of the watch. Most Casio watches have one to four screws. Turn the watch over so the back faces up, and use the correct screwdriver to turn each screw counterclockwise. Place each screw in a small cup or on a piece of tape so you do not lose them.
Once all screws are out, gently pry the case back away from the watch body using a flathead screwdriver or a plastic spoon. Do not use force — if it does not lift easily, you may have missed a screw. Some case backs are glued in addition to being screwed; if you feel strong resistance, stop and take the watch to a jeweler rather than risk cracking the plastic.
After the case back is off, you will see the battery sitting in a small metal or plastic holder. It is usually a thin silver disc, sometimes with a plastic tab attached. Note the orientation — the positive side (marked with a + or a flat surface) should face up or toward you.
Removing the old battery and installing the new one
If the battery has a plastic tab, pull the tab gently to lift the battery out. If there is no tab, use a plastic spoon or the edge of a flathead screwdriver to pry it out gently from the side. Do not use a metal tool directly on the battery itself, as you can damage it or create a short circuit.
Once the old battery is out, look at the code printed on it and confirm that your new battery matches. Insert the new battery into the holder with the positive side facing the same direction as the old one faced. Press it down gently until it sits flat and find in the holder.
Before you close the case back, press the crown (the button on the side of the watch) or any other button to test that the watch powers on. If it does not respond, remove the new battery, flip it over, and try again — you may have inserted it upside down. Once the watch responds, you are ready to close the case.
Closing the case back and testing the seal
Align the case back with the watch body so the screw holes line up. Press it down gently until it sits flush against the body. Insert each screw and turn it clockwise by hand first to make sure the threads catch — if a screw feels stuck or gritty, back it out and try again to avoid stripping the hole.
Once all screws are hand-tight, use the screwdriver to tighten them fully. They should be snug but not so tight that you are using all your strength — over-tightening can crack the plastic case back. A good rule is to stop as soon as you feel resistance.
After closing the case, wear the watch for a few hours and check it for any signs of water inside the crystal (fogging or droplets). If the watch is not water-resistant or is rated below 30 meters, this is not a concern. If it is rated 30 meters or higher and you see moisture, the seal may not be tight, and you should take it to a jeweler to reseal it.
When to take your Casio to a jeweler instead
If the case back is glued in addition to being screwed, do not try to force it open — you will crack the plastic. Take it to a jeweler or a Casio service center. The same applies if the screws are stripped or if you cannot find a screwdriver that fits without slipping.
Water-resistant watches rated above 30 meters (100 feet) should be opened and resealed by a professional, because the seal is critical to keeping water out. If you open one yourself and close it without a proper gasket or sealant, you risk water damage to the movement. A jeweler charges fifteen to thirty dollars to open, change the battery, and reseal a water-resistant watch — worth the cost to protect a watch you wear regularly.
If your Casio is still under warranty, check the warranty card before opening it yourself. Some warranties are voided by opening the case, though most consumer Casio watches do not have this restriction.
Common battery types for Casio watches
Casio uses a handful of standard battery types across its product lines. Digital sports watches and basic analog watches often use SR626SW (silver oxide), LR626 (alkaline), or CR2032 (lithium coin cell). The SR626SW is the most common and lasts longer than the LR626. The CR2032 is larger and appears in some digital models.
The battery code is always printed on the old battery itself, so you do not have to guess. If you cannot read the code because the battery is corroded or faded, take a photo of the watch model number (usually on the case back or inside the band) and search for the battery type online, or ask a battery retailer — they can often look it up by model.
Frequently Asked Questions
Can I use a different battery type if I cannot find the exact one?
No. Different battery types have different voltages and sizes, and using the wrong one can damage the watch movement or cause it to malfunction. Buy the exact type printed on the old battery. If your local store does not stock it, order it online — it usually arrives within a day or two and costs only a few dollars.
What should I do if I drop a screw inside the watch?
Stop when ready and take the watch to a jeweler. A loose screw inside the case can damage the movement or battery contacts. Do not shake the watch or try to retrieve it yourself. A jeweler can open the case safely and remove the screw without causing further damage.
How long does a Casio watch battery last?
Most Casio batteries last two to five years, depending on the type and how often you use features like the backlight or alarm. Silver oxide batteries (SR626SW) last longer than alkaline ones (LR626). The battery life is usually printed on the packaging when you buy a replacement.
Is it safe to open a water-resistant Casio watch myself?
Watches rated below 30 meters are generally safe to open at home. Watches rated 30 meters or higher should be opened by a jeweler, because resealing them correctly requires a gasket and tools you do not have. If you open a water-resistant watch yourself and do not reseal it properly, water can damage the movement.
What if the watch does not work after I put in the new battery?
First, remove the battery and flip it over — you may have inserted it upside down. If it still does not work, remove the battery, wait a few seconds, and reinsert it to make sure the contacts are clean. If the watch still does not respond, the battery may be defective or the watch movement may have a problem unrelated to the battery. Take it to a jeweler for diagnosis.