You can identify the right watch battery a few simple ways:

• Check the case back: Many watches have the battery code etched on the back or inside the case (e.g., 377/SR626SW, 364/SR621SW, 371/SR920SW, 395/SR927SW).
• Use the old battery: Carefully note the code printed on the cell before disposing of it.
• Consult the manual: The user guide or maker’s support page usually lists the exact size and chemistry.
• Match chemistry and size: Most watches use silver oxide button cells. Larger lithium coin cells (CR2016/2025/2032) are less common in standard wristwatches.

If your watch is water‑resistant, opening it can affect seals; a professional service may be advisable. Keep new cells in child‑resistant packaging and recycle used batteries per local guidelines.

DIY battery swaps are possible with care and the right tools:

1. Set up: Work on a clean, well‑lit surface with a soft pad. Have a case opener, small screwdriver, and non‑metallic tweezers.
2. Open the case: Snap backs lift with a case knife; screw backs need an adjustable wrench. Keep track of tiny screws and clips.
3. Note polarity: Photograph the battery before removal; the flat side is usually “+”.
4. Replace: Insert the new cell without touching faces; avoid shorting with metal tools. Ensure the movement’s hold‑down clip is secure.
5. Seal and test: Make sure the gasket is clean and seated. Close the case and check timekeeping and functions.

If your watch is water‑resistant, under warranty, or has complex features, a professional service can help preserve seals and performance. Keep batteries away from children and pets; coin cells can be hazardous if swallowed.

Costs can vary widely depending on several factors:

• Battery type: Silver oxide cells typically power most watches; specialty sizes or chemistries may differ in price.
• Service level: A quick swap is one thing; resealing gaskets and pressure testing water‑resistant models adds labor.
• Case design: Screw‑down backs, tiny screws, or integrated gaskets can take more time.
• Tools and supplies: Doing it yourself may require a case opener, tweezers, and a parts tray.
• Convenience and location: On‑the‑spot service or mail‑in options may price differently based on region and turnaround.

For DIY, multipacks can lower per‑cell cost if you’ll use them before expiration. For in‑person service, check what’s included (e.g., reseal, testing) and compare local providers for current rates.

Most watches use compact button or coin cells. Here’s a quick overview:

• Silver oxide (1.55V): The most common for analog and many digital quartz watches. Examples include sizes often labeled 377/SR626SW, 364/SR621SW, 371/SR920SW, and 395/SR927SW.
• Alkaline (1.5V): Same dimensions as some silver oxide cells (e.g., LR44/AG13) but typically shorter life and less stable voltage; often considered a temporary alternative.
• Lithium coin (3V): Larger cells like CR2016, CR2025, or CR2032 appear in some big digital watches and other small electronics, but are less common in standard wristwatches.
• Rechargeable packs: Smartwatches usually have built‑in rechargeable batteries and aren’t compatible with button cells.

Always match the exact size and chemistry listed by your watch manufacturer.

They’re the same size but not the same chemistry:

• LR44: An alkaline 1.5V cell. It fits many devices but typically has a sloping discharge curve and shorter life in watches.
• 357 (also 303/SR44): A silver oxide 1.55V cell. It usually provides a flatter, more stable voltage, which can support more consistent timekeeping and longer service intervals.

Many watches that accept this size perform better with silver oxide. Alkaline may work in a pinch, but it can require more frequent replacements. Always follow your watch’s manual, avoid mixing old and new cells, and recycle used batteries according to local guidelines. Results can vary by watch design and power demands.