What size screws for toilet seats?

When it comes time to replace or install a new toilet seat, one of the first questions that comes up is what size screws are needed to properly secure the seat to the toilet. Selecting the right screw size is important for ensuring a tight, wobble-free connection. This article will provide a quick overview of the common toilet seat screw sizes and types to help you choose the right ones for your toilet installation or replacement project.

Quick Answer

Most modern toilet seats use either 1/4-inch or 5/16-inch diameter screws. 1/4-inch is the most common residential size, while 5/16-inch provides extra stability for heavier commercial seats. The screw length also varies, with most falling between 1-1/4 to 2-1/4 inches. Matching the existing screw diameter and length is recommended when replacing a toilet seat. The screws should be metal rather than plastic and have a flat head, pan head, oval head, or hex washer head style.

Toilet Seat Screw Sizes

There are two main toilet seat screw diameter sizes:

• 1/4-inch diameter – This is the most widely used screw diameter for residential toilet seats. The smaller size is suitable for most standard round and elongated household toilets.
• 5/16-inch diameter – The slightly larger 5/16-inch size provides extra stability, making it the top choice for sturdier commercial toilet seats. Some residential models may also use 5/16-inch screws.

The 1/4-20 size refers to 1/4-inch diameter screws with 20 threads per inch, while 5/16-18 denotes 5/16-inch diameter screws with 18 threads per inch. Both are standard toilet seat screw thread sizes.

In addition to diameter, proper screw length is also important for a secure toilet seat installation. Common lengths include:

• 1-1/4 inches
• 1-1/2 inches
• 1-5/8 inches
• 2 inches
• 2-1/4 inches

The longest screws that don’t extend through the bottom of the porcelain toilet bowl are recommended. For most toilets, 1-1/2 to 2-1/4 inches is optimal. Measure the toilet bowl thickness if uncertain.

Matching Existing Screw Size

When replacing an existing toilet seat, using the same screw diameter and length as the original hardware is advised. This ensures the new seat can be installed without complications:

• Use a ruler to measure the diameter of the old screws or visually compare them to a new 1/4-inch or 5/16-inch screw.
• For length, either measure the old screw or its visible threaded area after removal. Select a replacement screw package with a similar length.
• Closely matching the original screws allows the new seat to align with the pre-drilled holes and fit securely against the bowl surface.

If the existing screw size cannot be determined, 1/4-inch diameter screws in a length between 1-1/2 to 2 inches should work for most residential toilets. Have a range of sizes on hand for testing during installation.

Screw Head Styles

Several toilet seat screw head styles allow a flush installation against the bowl:

• Flat head – Low profile flat top allows it sit flush.
• Oval head – Oval shape also sits flush on toilet seats.
• Pan head – Rounded top takes up the cavity behind the seat.
• Hex washer head – Allows use of a wrench for easier tightening.

Avoid screws with philips head, slot head, or other protruding tops that do not sit flush against the recess in the seat base. The head shape is not as crucial for the washers and nuts on the underside of the toilet bowl.

Metal vs Plastic Screws

Metal screws are required for proper toilet seat installation. Do not use plastic screws that come standard with some budget seats. Metal is stronger, more durable, and less likely to crack or shear off over time. Stainless steel screws offer maximum corrosion resistance for long life.

Tips for Proper Toilet Seat Screw Sizing

Some key tips for choosing and using toilet seat screws correctly include:

• Use 1/4-inch diameter screws for most residential toilet seats and 5/16-inch for heavier commercial seats.
• Measure existing seat screws or use 1-1/2 to 2-1/4 inch lengths for new installations.
• Select a flush-fit head shape like flat, oval, pan, or hex washer head.
• Always use corrosion-resistant metal screws rather than plastic.
• Avoid screws that are too short and fail to grab or too long that extend through the porcelain.
• Tighten screws evenly and firmly but not overtightened to avoid cracking porcelain.
• Fill unused screw holes on the toilet bowl with silicone sealant to prevent leaks.

How to Remove Stuck Toilet Seat Screws

Over time, toilet seat screws may become stubbornly stuck in place and very difficult to remove. Here are some tips for getting stuck screws out more easily:

• Use a penetrating oil like WD-40 to loosen the threads. Spray or drip it into the screw joints, let it soak for 10-15 minutes, then try unscrewing.
• Heat the screw area with a hairdryer to expand the metal. The expanded screws turn more freely.
• Place a rubber band or piece of an eraser between the screwdriver tip and screw head to improve grip.
• If the screw head is too stripped to grip, use locking pliers or Vise-Grips on the body.
• As a last resort, use a Dremel or hacksaw to cut a line in the screw head and remove it with a flathead screwdriver.

Preventing screws from seizing up is ideal. Apply thread lubricant periodically and avoid overtightening during installation.

Choosing Quality Toilet Seat Screws

While any appropriately-sized metal screw can work, going with a brand designed for toilet seats can offer some advantages:

• Corrosion-resistant materials like stainless steel for longevity.
• Proper flat or oval screw heads to fit toilet seat recesses.
• Wide range of diameters and lengths for easy matching.
• May come with pre-attached washers and nuts.
• Designed not to crack porcelain like generic screws.

Major plumbing brands like American Standard and Kohler sell their own replacement toilet seat screw kits featuring screws sized specifically for their seats. These make ideal replacements for their branded seats but can work for other seats too.

Conclusion

Choosing the proper toilet seat screw size is key to a wobble-free installation. For most seats, 1/4-inch diameter screws around 1-1/2 to 2-1/4 inches long provide an optimal fit. Matching the measurements of the existing screws is ideal for replacements. Stuck screws can be removed with some penetrating oil and the right techniques. Investing in quality corrosion-resistant screws specifically designed for toilet seats can provide a very secure and long-lasting fit.

Frequently Asked Questions

What are the most common toilet seat screw sizes?

The two most widely used toilet seat screw sizes are:

• 1/4-inch diameter
• 5/16-inch diameter

1/4-inch is standard for residential round and elongated seats. 5/16-inch offers extra stability for commercial seats.

How do I know if my toilet takes 1/4-inch or 5/16-inch screws?

You can determine your toilet seat screw diameter size in a few ways:

• Measure the existing screws with a ruler
• Visually compare to new 1/4-inch and 5/16-inch screws
• Test fit both sizes in the pre-drilled holes
• Consult the toilet or seat manufacturer specifications

1/4-inch is the standard for household toilets unless otherwise specified.

What screw length should I use for a toilet seat?

Recommended toilet seat screw lengths include:

• 1-1/4 inches
• 1-1/2 inches
• 1-5/8 inches
• 2 inches
• 2-1/4 inches

The longest screws that don’t protrude through the bottom of the toilet bowl are ideal. 1-1/2 to 2-1/4 inches suits most residential toilets.

Can I use plastic screws for my toilet seat?

Plastic screws that come standard with some toilet seats are not recommended. Metal screws like stainless steel are much stronger and less likely to break or strip. For a durable and secure installation, metal screws are required.

How do I remove rusted, stuck toilet seat screws?

For removing stuck toilet seat screws, try these approaches:

• Apply penetrating oil like WD-40 and let it soak in for 10-15 minutes
• Heat the area with a hairdryer then try unscrewing
• Improve grip with a rubber band around the screwdriver tip
• Use locking pliers or Vise-Grips on a stripped screw body
• Cut a line in a damaged screw head with a Dremel

Toilet Seat Screw Sizes Comparison Chart

Screw Size	Screw Diameter	Use Cases
1/4-20	1/4 inch	Most round and elongated residential toilet seats
5/16-18	5/16 inch	Heavier commercial toilet seats needing more stability

Toilet Seat Screw Length Comparison

Screw Length	Best Use Cases
1-1/4 inches	Very thin toilet bowls
1-1/2 inches	Good general purpose length
1-5/8 inches	Slightly thicker toilet bowls
2 inches	Average modern toilet bowls
2-1/4 inches	Thickest porcelain toilet bowls

Toilet Seat Screw Head Styles

Screw Head	Characteristics
Flat Head	Thin profile sits flush with seat
Oval Head	Oval shape also fits flush
Pan Head	Rounded top fills recessed cavity
Hex Washer Head	Allows use of wrench for tightening

The head shape is not as important for washers and nuts on the underside. A low profile head that sits flush is crucial for screws through the seat.

Metal vs. Plastic Toilet Seat Screws

Screw Material	Pros	Cons
Metal	Very strong and durable Stainless steel resists corrosion Less likely to shear off	More expensive
Plastic	Lower cost with new seats	Prone to cracking and breaking Can strip out over tightening Not as strong or stable

Metal screws are highly recommended over plastic for toilet seat installation whenever possible.