toilet flange

Toilet Flange Dimensions

The toilet flange that you use is important for sealing the bathroom floor. You use the flange to connect your toilet drain to the piping in your house.

It is also responsible for keeping your toilet in place.

Toilet flanges come in a standard size of 3 or 4 inches. They can be slid into a drain pipe or fitted over the top.

There are also multiple different materials that flanges can be made out of.

What Is The Standard Toilet Flange Size?

toilet flange size

Flanges come in just two standard sizes: 3 and 4 inches. You’re most likely to find 4×3 flanges when you look in a local hardware store.

This model has two different diameters.

The first diameter is the one that connects to your toilet. This is four inches.

It should be able to fit to the vast majority of toilet models. Then the bottom of the flange connects to the drain pipe.

This is just 3 inches, since it’s built to connect to a standard 40 size pipe.

There are some flanges that are just 3 inches on both the bottom and top. Because the size is the same for both openings, these are very easy to install.

But you should only use them if your toilet has a 3 inch pipe. Using the wrong sized flange can have a negative impact on your piping’s alignment.

Very rarely, you might find a 4×4 flange, which has four inch diameters on both sides. But this will typically only be used in more industrial applications.

Are There Different Size Toilet Flanges?

The standard size of a flange remains the same. You’re most likely to use a 3×4 inch flange, but you can also find 3×3 and 4×4 inch options.

You will occasionally find strange flange sizes that are larger or smaller than the standard size. For example, ABS plastic flanges have a 7 inch opening and 3.5 inch bottom.

If you get one of these, you’ll need to use an extension kit to adjust the flange height.

This can be a pain and more trouble than it’s really worth. It’s better to just get the appropriate standard size for your toilet.

Should You Use A 3 Or 4 Inch Toilet Flange?

The right flange size depends somewhat on your toilet and your piping. The most common type of flange actually has openings of both 3 and 4 inches in diameter.

It is wider on the top than the bottom, which allows it to fit to wider toilet models.

If your drain pipe is 4 inches rather than 3, though, you’ll need a 4×4 flange. Four-inch drain pipes are able to carry away more waste, and they’re typically used when several toilets are connected to the same pipe.

How Is Toilet Drain Diameter Measured?

The diameter is measured across the widest part of the flange.

Since the flange connects the toilet drain to the household piping, there are two openings. You’ll typically find sizes of 3×3, 4×4, or 4×3. These describe the diameter of each opening.

Toilets should have standardized drain sizes, but you can check the specs of your model to make sure that there’s nothing unusual happening.

Types Of Toilet Flanges

Though the sizing of toilet flanges tends to be pretty standard, there are six different materials that the models might be made from. Each has its own unique benefits and drawbacks.

Copper Toilet Flanges

copper toilet flange

Copper flanges have a high level of durability because of their corrosion resistance. Some models are flexible, allowing them to be molded to the piping.

Others are rigid.

The softer the model, the easier it will be to install. If you’re working with hard copper, you will need to use elbow joints to seal the model to the pipe.

Copper is naturally antifungal and antibacterial, which makes it a good choice for your plumbing.

Brass Toilet Flanges

brass toilet flange

Brass is crafted from a mixture of copper and zinc, which makes it very durable. It is resistant to both corrosion and rust.

In addition, it is a highly malleable material. You can purchase circular brass flanges or flanges that include elbow joints, which let you attach the pipe more easily.

One of the biggest potential drawbacks of brass is that it might oxidize when it’s exposed to the air, leading to a change in color over time. The material also tends to be heavy.

PVC Plastic Toilet Flanges

pvc toilet flange

You might be surprised to learn that PVC plastic is the most common choice used for toilet flanges. But you shouldn’t be.

Not only can these flanges be customized to basically any drain setup, but they are also extremely affordable.

PVC plastic is super lightweight, and it can be used in both commercial and residential applications. It also tends to be more durable than typical plastic.

There are some flanges available in ABS plastic, which is so tough that it’s sometimes used in the construction of airplanes!

ABS plastic is more expensive than PVC, but it’s better at dealing with very bulky waste.

Some plastic models are crafted from 100 percent plastic, but there are also models that have metal on the top to help with the fit.

The biggest drawback of plastic is that it is most likely to become damaged with exposure to high pressure.

Stainless Steel Toilet Flanges

Stainless Steel Toilet Flanges

Stainless steel is a popular choice for kitchen appliances, but it can also be used in the bathroom. This material is corrosion and rust resistant.

It also seals better than the majority of flange models.

However, most “stainless steel” flanges only have stainless steel around the wax ring. The rest of the model is crafted from copper, plastic, or iron.

There are several different kinds of stainless steel. The most advanced types include silicone , which lowers the chances of oxidation.

Stainless steel is significantly lighter in weight than brass.

Cast Iron Toilet Flanges

Cast Iron Toilet Flanges

The biggest thing to know about cast iron flanges is that they are built for cast iron pipes alone. If you don’t have a cast iron piping system, this flange will be basically useless to you.

A cast iron flange has a different shape. It is elongated so that it can fit more securely into the pipe.

This type of flange works best when your piping is below the subfloor.

Cast iron is the fastest-rusting of the six materials.

Aluminum Toilet Flanges

Aluminum Toilet Flanges

Aluminum is sturdy and resistant to corrosion. It is also lightweight while being significantly less expensive than stainless steel.

Like stainless steel, most aluminum designs only encompass the wax ring, although there are models that are crafted 100 percent from the material.

Unadulterated aluminum is the best kind. But if the material is mixed with metals like zinc or copper, it might become more durable.


Toilet flanges typically come in standard sizes of 4×3 inches, although you can find some odd sizes along the way.

You want to make sure that the model you choose will be able to connect your toilet to your home piping system. Thanks to the standardization, that shouldn’t be an issue for most models.