The battery size depends on your car's make and model, not the fob itself

Key fob batteries come in a handful of standard sizes, and the one your fob needs is determined by who made your car, not by the shape or brand of the fob. The most common sizes are CR2032, CR2025, and CR2016 — all coin-cell batteries about the size of a dime. Some luxury vehicles and older cars use different sizes like CR2430 or even AA and AAA batteries, but those are less common.

The fastest way to know which one you need is to open your fob and look at the battery itself — the size is printed right on it. If you've already removed the old battery and can't read it, your owner's manual lists the correct size, or you can call your car's dealership with your vehicle identification number (VIN) and they'll tell you in seconds.

Key Takeaways

  • CR2032 is the most common key fob battery size across all car brands, followed by CR2025 and CR2016.
  • The correct size is printed on the battery itself, so opening your fob is the quickest way to confirm what you need.
  • Your owner's manual and your car's dealership both have the battery size on file if you can't read the old battery.
  • Coin-cell batteries (CR series) cost between $3 and $8 at drugstores, grocery stores, and online retailers.
  • Battery life in a key fob is typically three to four years, depending on how often you use the buttons.

How to identify the battery size without opening the fob

If you want to know the size before you crack open your fob, start with your owner's manual. Search the index for "key fob" or "remote battery" — most manuals have a one-line entry that names the exact size. The manual is usually in your glove box, but if it's not there, you can read a PDF from your car manufacturer's website using your VIN.

Your dealership's parts department is another reliable source. Call with your VIN and year, make, and model, and they can tell you the battery size without you having to visit. Some dealerships will even sell you the battery on the spot, though it's usually cheaper to buy it at a pharmacy or supermarket.

If you're buying a replacement fob from a third-party seller (not the dealership), the product listing or packaging should state the battery size. Check before you buy, because not all aftermarket fobs use the same battery as the original.

The most common key fob battery sizes and where they fit

CR2032 is by far the most common. It's used in the vast majority of cars made in the last 20 years — Honda, Toyota, Ford, Chevrolet, BMW, Mercedes, Audi, and many others all use it as their standard. If you had to guess, CR2032 is the safest bet.

CR2025 is slightly thinner than the CR2032 but the same diameter. Some vehicles use it instead of the CR2032, and it will physically fit in a CR2032 slot, but it won't last as long because it has less capacity. Don't use a CR2025 if your fob calls for a CR2032.

CR2016 is thinner still and used in some older vehicles and compact fobs. It's less common than the other two but still widely stocked.

CR2430 is larger and used in some luxury vehicles and high-end aftermarket fobs. It's less common in stores, so if your fob needs one, order it online or ask your dealership to stock it.

AA and AAA batteries appear in some older cars and a few modern ones, usually in fobs that are larger or have extra features. These are straightforward to find anywhere, but confirm the size before you assume.

How to open your fob and check the battery

Most key fobs open with a small flathead screwdriver or a coin. Look for a seam or slot on the edge of the fob — that's usually where you insert the tool and gently pry. Some fobs have a small button or latch on the back that you press to pop the case open. Don't force it; if it's not moving, you're probably prying in the wrong spot.

Once the fob is open, the battery is usually sitting in a small compartment, often held in by a metal clip or spring. The size is printed on the flat face of the battery — you'll see something like "CR2032" or "3V" stamped or printed there. Write it down or take a photo before you remove it.

When you're ready to replace it, note which side was facing up (usually the flat side with the printing), because the battery needs to go back in the same way. Most coin-cell batteries have a positive side (marked with a +) and a negative side, and installing it backwards won't damage the fob, but it won't work either.

Where to buy replacement key fob batteries

Coin-cell batteries are sold everywhere: pharmacies like CVS and Walgreens, supermarkets, hardware stores, and online retailers like Amazon. A single CR2032 costs between $3 and $8 depending on the brand and where you shop. Name brands like Energizer and Duracell are more expensive than store brands, but they all perform the same way in a key fob.

Your car's dealership sells them too, usually for $5 to $10, and they can install it for you if you don't want to do it yourself. Some dealerships charge a small service fee (usually $10 to $20) for the installation, so it's worth asking the price before you agree.

If you need an unusual size like CR2430, check online first — local stores may not stock it. Amazon, eBay, and battery specialty sites usually have everything in stock and ship within a few days.

How long key fob batteries last and when to replace them

A typical key fob battery lasts three to four years with normal use. If you use your fob several times a day, it may wear out faster. If you use it rarely, it might last longer. The battery doesn't die suddenly — instead, the range of the fob gets shorter, or you have to press the button harder or multiple times to get a response.

When you notice the fob isn't working as well as it used to, it's time to replace the battery. It's a five-minute job: open the fob, remove the old battery, drop in the new one, and close it back up. You don't need any tools except the screwdriver or coin to open the case.

If replacing the battery doesn't fix the problem — if the fob still doesn't work or only works intermittently — the issue is likely with the fob's electronics or your car's receiver, not the battery. In that case, you'll need a replacement fob from your dealership or a third-party seller.

Frequently Asked Questions

Can I use a different battery size if I don't have the right one?

No. Using the wrong size can damage the fob or prevent it from working at all. The battery needs to fit snugly in the compartment and make proper contact with the springs or clips. A battery that's too small won't make contact; one that's too large won't fit. Always use the exact size your fob calls for.

What should I do with the old battery?

Coin-cell batteries contain small amounts of lithium and should not go in the trash. Most pharmacies and supermarkets have battery recycling bins near the checkout or customer service desk. Some Best Buy locations also accept batteries. Check Earth911.com or call your local waste management to find a drop-off site near you.

Is it cheaper to replace the battery or buy a new fob?

Replacing the battery costs $3 to $10 and takes five minutes. A new fob from the dealership costs $150 to $400 and requires programming. Always try a new battery first — it solves the problem 90 percent of the time.

Will my fob stop working if I leave the battery out for a while?

No. The fob won't work without a battery, but removing the battery won't erase any programming or damage the fob. You can leave it out as long as you need to. When you put a new battery in, the fob will work when ready.

Can I use rechargeable batteries in my key fob?

Rechargeable coin-cell batteries exist, but they're not recommended for key fobs. They have a lower voltage than disposable batteries and may not provide enough power to transmit a signal reliably. Stick with standard disposable coin-cell batteries for consistent performance.