Since several sink plug sizes are available at home improvement stores, it's best to know ahead of time which size suits your sink, instead of just guessing and grabbing one off the shelf. Finding a stopper that fits your sink is easiest if you have the original paperwork that came with the sink or stopper assembly, so you are able to purchase an exact replacement. Otherwise, most hardware or plumbing stores sell common replacement stoppers.
To find a stopper that fits your sink, take the old one to the store when shopping for a new one. If that isn't an option, measure the diameter of the drain opening and purchase a stopper that spans that size.
Bathroom Sink Drain Hole Sizes
There is no universal drain hole diameter that applies to every bathroom sink, but 1 1/2 inches is the most common size for a bathroom sink drain opening, according to Signature Hardware. Some bathroom sinks have a slightly narrower opening at 1 1/4 inches, while others are a bit wider at 1 5/8 inches.
A vessel sink drain hole size often runs a little larger than those in freestanding sinks or sinks mounted into a vanity. For vessel sinks, which sit atop, rather than in, the counter or vanity, the opening is usually 1 5/8 to 1 1/4 inches wide.
Finding the Correct Sink Stopper
If you still have the literature that came with the sink or drain assembly, it should list the drain opening size and size of the stopper. Otherwise, just measure across the center of the opening with a tape measure. If there is a stopper in the sink already, measure the top of it or remove the stopper and take it to a local hardware store. For a pop-up bathroom sink stopper, which uses a lever to lift or raise the stopper, measure both the head and the length of the entire stopper, as well as take note of its construction.
It's easiest to purchase replacement suction-style stoppers that simply lift out of the sink when not needed. The "right size" for this type of stopper is any diameter larger than the drain opening. Other inexpensive, old-fashioned rubber stoppers are another option, as they press into the drain opening to block water and lift out to allow water to flow through. Some stores sell these in multi-packs of common sizes. Many of these plugs are tapered at the bottom, so you should be able to find one spanning one or two common hole sizes, including the size of your sink's drain opening.
Kitchen Sink Standards
Kitchen sink drain openings are usually a standard 3 1/2 inches across, although in rare cases, they may be 4 inches wide. A plug with a built-in strainer is a common option, allowing water to flow through when desired. This is also a great choice to help keep debris from entering the drain. Stores also sell the replacement stoppers that go over garbage disposal openings.
The Universal Sink Plug
A universal sink plug is designed to fit multiple drain-hole sizes. These are often suction-style covers, placed over the drain opening and pressed down to keep water in the sink basin. Even with "universal" in the name, not all of these plugs are the same size. For the most bang for the buck, look for one wider than the widest drain opening in your home. This way, it can fit virtually any sink or even the bathtub. Some of these are up to 5 inches across and also come in handy for frequent travels.
Kathy Adams is an award-winning writer. She is an avid DIYer that is equally at home repurposing random objects into new, useful creations as she is at supporting community gardening efforts and writing about healthy alternatives to household chemicals. She's written numerous DIY articles for paint and decor companies, as well as for Black + Decker, Hunker, SFGate, Landlordology and others.