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Standard Toilet Flange Dimensions? (All You Need to Know)

Without a toilet flange, connecting your toilet with the grounding pipe can’t be possible. It’s a connector and plays a vital role in every connection point. But you need to choose the best-sized toilet flange since there are different types and sizes available.

You cannot replace or change the toilet flange every month or year. It lasts for years if you can choose the best quality and ensure the best fitting. A little care would be appreciated as well.

What are the standard toilet flange dimensions?

4 and 3 are the standard toilet flange dimensions. Mainly it is 4*3. 4 inch remains on the ground to fit with the toilet, and the 3-inch mouth is placed under the ground to fit with the pipeline. Some other dimensions are also available, but they are not usual. Only odd size pipes need them.

Since the pipe size is not universal, and people sometimes use different odd-sized pipes and toilets, I will give all the available flange dimensions here so that you can find the perfect dimension according to your needs.

4*3 inch Dimension:

Most toilet pipe comes with a 4inch mouth, and the ground pipeline remains 3inch. Therefore, the standard and most used toilet flange dimensions are 4*3 inches. If you plan to install a new toilet, you must use the standard-sized toilet flange.

It will help you when you need to change the flange in the near future. It will be available at any hardware shop, but the other size dimension might be difficult to buy. It’s why people buy and suggest the standard size toilet flange.

3-inch Flange:

Another usable dimension is 3 inches. A single pipe flange comes with 3-inch dimensions. It gives both an opener and a closer 3-inch dimension, and it can bear the high pressure of the toilet when you use the flash.

But it’s not the standard size. And the extra pressure might damage the flange within a month or year. So, that’s the issue of using a 3-inch dimension flange.

4inch Dimension:

You can buy only the 4-inch dimension toilet flange that will fit in both the 3-inch pipe and the 4-inch pipe. And, it gives you the best support along with a comfortable fit. But you don’t get the best fit.

The best fit only comes with the 4*3 inch dimension that you talk about in the first place. However, the 4inch dimension is far better than the 3 inch one. It’s not the best one but not the worst one either.

Odd-Size Dimension:

Some PVC pipe fitting comes with 3 ½ inch ground diameter and 7-inch toilet diameter. It’s a very unusual and unpopular pipe as well—very few toilet pipes or draining pipes come with this requirement, known as the odd-size dimension.

You will find it in the hardware shop indeed, but it will be costly, and you need to search here and there. It’s not any standard size dimension anymore. If you have a chance, you should avoid it and go for the 4*3 inch dimension.

What are the different shapes of toilet flanges available?

Different shapes of toilet flanges are available in the market. Let’s see what they are.


The regular toilet flange is the most common and most used shape. It gives you the best fittings and the best draining as well. When you buy the toilet flange, be sure to purchase the regular shape. It’s better and more reliable as well.

The mouth of the regular shape flange ensures 4 inches, and the bottom comes with a 3inch fitting size. It’s the ideal fitting shape for all the toilet flanges, but more are in the rows. You can select them if you need them.

Deep Seal:

A deep seal is another best shape for a toilet flange. Although it’s not a widely used drain pipe for toilets, it is an ideal shape for other purposes.

It’s more like the P-Shaped connectors that connect and pass much water at times. If you have large fittings, and the regular one can’t do its job, a Deep seal would be an excellent option.

It’s a curved pipe connector made of PVC pipe. Most of the PVC pipe connector uses the Deep Seal shape toilet flange for their convenience. But it might be an issue if you don’t have the other options and have little space.

Offset Shape:

It is another shape for the toilet flange. Mainly, the offset shape is more like a bend and different than the 90° pipeline. It is an elbow shaped pipeline that you can also connect the toilet to the ground pipe. It will give you the best fittings and secure fit.

But it’s not the regular one. So, you cannot use the Offset shape toilet flange in any toilet. You have to look at your toilet pipes and select the right shaped-flange accordingly.

How do I know what size toilet flange I need?

To know your toilet flange size, you have to measure the ground pipe or the drain pipe size and the toilet size. Typically, the ground pipe comes with a 3-inch opener, and the toilet pipe size comes with a 4-inch opener. Therefore, the 4*3 inch dimension fits most of the toilet.

It might be different if you have a bigger toilet and the drain pipe is odd. In that case, you need to measure the pipe mouth and the toilet manually. Then, you will have the actual size of the fitting pipes. Once you know the exact size, you can buy the perfect match toilet flange.

How do you measure a toilet flange?

Measuring a toilet flange is not difficult; you have to use a scale and get the job done within a minute.

Measure the Toilet Pipe:

Your first job is to measure the toilet pipe. You will get a pipe already installed at the bottom when you buy the toilet. That’s the first area that you need to measure. Maybe it will be around 3 or 4 inches unless you buy the odd size toilet.

Measure the Drain Pipe:

After getting the toilet bottom pipe measure, it’s time to measure the drain pipe. You must have a ground pipe that you need to measure. Take your scale and get the measurement of the ground drain pipe.

Once you get these two measurements, you’re good to go. Typically, the drain pipe comes with three inc mouth fitting. So far, that will be the last thing you need to find out. Now you get both the measurement of the drain pipe and toilet end pipe.

The perfect size of your toilet flange would be around 4*3 inches for the regular fitting pipe. You can buy the different toilet flanges accordingly if you have different measurements.

What size hole do I need for a toilet flange?

You need a 4-inches hole for a toilet flange. It will suit both 3 and 4 inches toilet pipe and the end pipe. You can consider the 4-inches as the universal and widely used toilet flange holes that can suit most of the toilet.

You will also find a 3-inch hole compatible with the toilet and drain pipe. But that’s not the regular size. You need to measure the toilet and drain line. Only then can you decide to buy a 3-inch hole toilet flange.

Another size is also available: a 3 ½ inch hole. This hole is compatible with the odd size toilet bottom pipe and the drainpipe. Sometimes, we buy an unusual size toilet that comes with a different size pipe. They will fit in a 3 ½ inch hole.

What size screws and bolts are needed for a toilet flange?

1 ½ size screws and bolts are needed for a toilet flange. It’s the regular size that people and plumbers mostly use to install their toilet flange. If you find any dissimilarities and cannot place these size screws and bolts, you must try with 1-inch screws.

Sometimes, the toilet and drain pipe comes in slightly different sizes. In that case, one-inch screws and bolts will be suitable. And they can firmly join your toilet and drain pipe with the toilet flange.

A toilet flange might be in a bent shape or odd shape. In that case, the screws and bolt size will vary. You have to ask the hardware shopkeeper to suggest the best-sized screws and bolts for that particular shape of toilet flange.

Final thoughts

4 & 3 are the best standard size toilet flange dimensions. You can use a 4*3 size flange in every toilet. If the toilet comes with an odd-sized pipe and you use a different size drain pipe, you need to measure them separately. Then, you get the right size. And the flange shape will differ.