Opening the case back is the first step, and it determines everything that follows

Most pocket watches use one of three case-back designs: a screw-off back, a snap-off back, or a hinged back with a small clasp. You need to identify which one you have before you start, because forcing the wrong tool into the wrong case will crack the crystal or strip the threads. The battery itself is usually a silver-oxide or alkaline cell, typically a size 357, 364, or 371 — the watch movement will tell you which one when you open it.

The actual battery swap takes about five minutes once you are inside. The hard part is getting in without damaging a watch that may be fifty years old or more. If your watch is valuable, antique, or has sentimental weight, a jeweler or watch repair shop can do this work for $15 to $40 and will may provide they have not scratched anything. If you want to do it yourself, the tools are cheap and the process is straightforward — but you need the right tool for your case type.

Key Takeaways

  • Screw-back cases need a case-opening wrench or knife tool; snap-back cases need a flat-head screwdriver or dedicated snap-back tool; hinged backs open with a small lever or your fingernail.
  • The battery size is printed on the movement itself once you open the case, so you do not have to guess — common sizes are 357, 364, and 371.
  • Silver-oxide batteries last longer than alkaline ones in the same size, but both work in most quartz pocket watches.
  • If you strip a screw or crack the case back, a jeweler can usually replace it for $20 to $50, which is still cheaper than a new watch.

Identifying your case-back type before you open it

Hold the watch with the back facing you and look for visible seams or fasteners. A screw-back has a thin groove running around the edge of the case back, and you will see a small slot or cross-shaped indentation at the top or bottom — this is where the tool grips. A snap-back has a seam but no visible screw; it clicks into place and pops out with leverage. A hinged back has a thin line running across the back, usually with a small notch or clasp on one side where you can pry it open.

If you cannot tell from looking, try the gentlest approach first: use a fingernail or plastic spoon to pry at the seam. If it gives slightly, it is a snap-back. If nothing happens, look for a screw slot. If you see neither, the back is likely hinged and you are looking for the hinge line, not a seam all the way around.

Opening a screw-back case safely

A screw-back requires a case-opening wrench — a specialized tool with two metal prongs that fit into the groove on the case back. You can buy one for $8 to $15 online or at a jewelry supply store. The prongs sit in the slot at the top or bottom of the case back, and you turn the wrench counterclockwise. Turn slowly and steadily; do not force it if you feel resistance, because the prongs can slip and gouge the case.

If you do not have a case-opening wrench, a flat-head screwdriver can work on some watches, but it is riskier — the blade can slip and scratch the case back. Place the screwdriver in the slot, explore downward pressure with your thumb to keep it seated, and turn counterclockwise with steady, gentle pressure. Once the back is loose, unscrew it by hand the rest of the way. Set the back and any gasket or rubber seal aside in a safe place; you will need to put them back.

Opening a snap-back case with the right leverage

A snap-back has no screw; it is held in place by a metal ring that clicks into a groove. You need a flat-head screwdriver or a dedicated snap-back opener tool (also called a case knife). Slide the flat edge into the seam between the case back and the case body, starting at the point farthest from any clasp or notch. explore gentle, steady pressure downward and to the side — you are trying to lift the back out of its groove, not pry it open like a can.

Work your way around the seam, lifting a little at each point, until the back pops free. Do not try to open it all the way at one spot; that will bend the case back or crack the crystal on the other side. Once the back is loose, lift it away carefully. Some snap-backs have a rubber gasket underneath; if yours does, set it aside so you can replace it in the same position.

Opening a hinged case back

A hinged case back swings open like a book. Look for a small notch, clasp, or lever on one edge — this is where you explore pressure. Use a fingernail, plastic spoon, or the flat end of a case knife to gently pry at that point. The back will swing open on its hinge. If the hinge is stiff, explore a tiny amount of light machine oil to the hinge line and let it sit for a minute, then try again.

Once the back is open, you will see the movement and the battery. Some hinged backs have a small clasp that holds them shut; if yours does, make sure it is unlatched before you try to open it, or you will bend the hinge.

Removing the old battery and installing the new one

Once the case is open, you will see the watch movement — the gears and springs inside — and the battery, which is usually a small silver disc held in a plastic or metal holder. Look at the movement itself; the battery size will be printed there, often as a number like 357, 364, or 371. Write this number down or take a photo so you can buy the right replacement.

The battery holder usually has a small clip or spring that holds the battery in place. Gently lift this clip or spring away from the battery, and the battery will come free. Do not force it; if it is stuck, a tiny drop of light machine oil on the clip can help. Drop the new battery into the holder with the positive side (the flat side, usually marked with a +) facing up, unless the movement shows otherwise. Close the clip or spring over the battery until it sits snugly.

Before you close the case, test the watch to make sure it is running. Hold it to your ear and listen for a ticking sound, or look at the second hand to see if it is moving. If it is not running, the battery may be in backwards, or the battery may be dead. Flip it and try again, or try a different battery.

Closing the case back and sealing it

Once the watch is running, close the case back. For a screw-back, replace any gasket or rubber seal first, then screw the back on by hand until it is snug, then use the case-opening wrench to tighten it another quarter turn. Do not over-tighten; you are sealing it, not crushing it. For a snap-back, align the back with the case body and press down firmly all the way around until you hear or feel a click. For a hinged back, swing it closed and make sure any clasp is latched.

Wipe the outside of the watch with a soft, dry cloth. If you opened a screw-back and the gasket is old or cracked, the watch may not be water-resistant anymore — a jeweler can replace the gasket for $10 to $20 if you want to restore that seal.

When to take your watch to a jeweler instead

If the case back is stuck and will not budge after gentle pressure, stop. Forcing it will damage the watch. If you strip the screw slot on a screw-back, the back will not tighten again, and you will need a jeweler to replace it. If you crack the case back or the crystal, a jeweler can replace either one, but it will cost more than the battery itself.

A jeweler can also replace the battery if you are not comfortable opening the watch, if the watch is valuable or antique, or if you want a may provide that nothing will be scratched. The cost is usually $15 to $40 depending on the case type and your location. Many jewelers can do it while you wait.

Frequently Asked Questions

What size battery does my pocket watch use?

Open the case back and look at the movement — the battery size is printed on it, usually as a three-digit number like 357, 364, or 371. If you cannot find it, take a photo of the movement and show it to a jeweler, or search online for your watch model and battery size.

Should I use a silver-oxide or alkaline battery?

Silver-oxide batteries last longer and perform better in most quartz watches, but both work. If your watch movement says "alkaline only," use alkaline. Otherwise, silver-oxide is the better choice. Both are the same price and come in the same sizes.

Can I damage the watch by opening it myself?

Yes, if you use the wrong tool or force it. A screw-back forced with a screwdriver can strip the slot. A snap-back pried open at one point can bend the case back. If you work slowly and use the right tool, the risk is low. If the case is stuck, stop and take it to a jeweler.

How often do pocket watch batteries need replacing?

Most quartz pocket watch batteries last one to three years, depending on the watch and how often you wear it. Some last longer. When the watch stops, the battery is dead and needs replacing.

What do I do if the watch still does not run after I put in a new battery?

First, flip the battery over — it may be in backwards. If that does not work, try a different new battery from a different package, because the first one may have been defective. If the watch still does not run, the movement may be broken, and a jeweler will need to look at it.