How To Measure A Toilet Flapper?

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Last Updated on September 26, 2022 by acechapman

Toilet flappers can last a long time but, they can wear out. Knowing how to measure your toilet flapper before replacing it is essential.

Today’s toilet flappers are more universal than they were in the 1900s when all toilet flappers were common. Toilet flappers come in sizes ranging from 2 to 4 inches and have different designs. They can also be made of different materials.

Turn off the water supply to your toilet and flush the tank. Then, measure the size of the flapper. Then, measure the diameter of the opening for the flush valve at the bottom of your tank. Older toilet models have a 2-inch flush valve, while newer models have a 3 to 4-inch flush valve.

You will need a 2-inch flapper if you have a reading of 2 inches. The same applies to readings of 3 or 4 inches.

Korky and Fluidmaster manufacture standards/universal toilet flappers are just as good as the ones made by original toilet manufacturers. The toilet flappers can fit in any toilet as long as they are the right size.

Because a toilet flapper is placed on top of the flush opening, it’s easiest to measure the opening size.

The toilet flapper is still easy to measure, but it is conical-shaped so it can be difficult to get the right measurement. You can measure the flush valve opening by simply placing tape over it.

You don’t need a measuring tape, or you don’t want to measure the flapper by hand. Here’s a trick that will help you determine if your flapper is 2-inch or 3-inch.

how to measure toilet flapper

How to Determine the Size of Your Toilet Flapper

Compare the size of your toilet flapper to determine if it is a 2-inch or 3-inch one. A 2-inch flapper is sufficient if the flapper is larger than a baseball bat or an orange fruit. You will need a 3-inch flapper if the flapper is smaller than a softball, grapefruit, or softball.

You can also remove the old flapper and bring it to your local home improvement store to determine the size. The experts at home improvement will provide a replacement for your toilet flapper.

The size of your toilet flapper will also depend on how much water you use. A toilet that uses 1.28 gallons of water per flush will need a 3-inch flush valve. Toilets with 1.6 GPF may have a 2-inch or 3-inch flapper, but toilets with 3.5 GPF will have a 2-inch flapper.

A 2-inch flapper may be available for toilets manufactured prior to 2005. Toilets made after 2005 (introduction WaterSense toilets), will most likely have a 3-inch flush valve.

Toilets with larger flush valves and therefore bigger flappers were created to allow water to flow quickly from the tank to the bowl.

This creates a stronger siphon and powerful flushing toilets. This allows for stronger flushing toilets, which use less water.

Modern toilets usually have a 3-inch flush valve, while toilets such as the American Standard Champion 4 have a 4-inch flush valve. An experienced person can simply look at a toilet flapper to determine its size.


To determine the size of the toilet flapper that you require, first, remove the tank from the tank. Next, measure the opening of the flush valve.


Without turning off the water supply to the toilet, you can’t remove a flapper from a toilet. The flush valve will allow water to continuously flow from the tank to its bowl.

An oval-shaped knob will be found on the wall behind your toilet. This is the shutoff valve for the toilet and you should turn it clockwise. To turn off the water supply, push/pull shutoff valves require that you pull the knob inwards.

To remove as much water from the tank as possible, flush the toilet and keep the handle down.


  • Take off the lid of your toilet tank and store it in a place where it will not fall or break.
  • Disconnect the flapper lift chain from the flushing handle. Once the flapper lift chain is disconnected, simply drop it inside the tank
  • Toilet flapper 2 has two ears that connect to the 2 flush valve pegs. Take the flapper ears off the pegs and remove them.
  • Place it on a bench.

There are two ways to measure the size of a toilet flapper. Either measure the flapper or the opening of the flush valve. You will learn how to measure both the flapper and the flush valve opening.


  • Measure the inside diameter with a ruler or measuring tape.
  • A 2-inch flush valve is one that measures between 1.8 and 2.33 inches. Buy a 2-inch flapper for your toilet.
  • If the reading is greater than or equal to 3 inches, it means that you have a 3-inch flush hose and will need a 3-inch flapper.
  • If your toilet valve is larger than 3 inches, you will need a 4-inch flapper.
how to measure toilet flapper


It can be difficult to measure the size of a toilet flapper so it is important that you are careful or you might end up with the wrong size flapper.

Either measure the length or the width of the flapper, from one end to the other. It is easier to measure the size of the flapper end to end.

If you measure the cone’s width, the reading will be straightforward. You can buy a flapper measuring 3 inches if you have a reading of 2 inches.

If you measure the flapper’s width from the end to end, buy a 2-inch flapper if you have 3 inches reading. A 3-inch flapper is recommended if you have 4 inches reading.

It is very easy to install the flapper after you have purchased it. Simply place the flapper over the opening of the flush valve, hook the ears to the pegs, and then connect the lift cable to the flush handle arm.

You should allow the lift chain to move freely. It should not be too tight as it can cause the flapper to come off the flush valve, causing leaks. If the lift chain is too loose, it won’t lift the flapper completely during flushing, which results in a weak flushing toilet.

Ideal lift chains should have a minimum of 1/2 inch of slack.

Wrapping Up

You won’t have to change the flapper every day. Most people don’t change their flappers on the toilet.

Sometimes, a flapper can wear out and leak. Rubber can flake over time and stop doing its job. There’s a good possibility that your toilet is running because of a flapper!

You can easily replace your flapper, without having to risk your valves.

New toilets have a 3-inch flapper, while older toilets that use more than 3 gallons per flush use a 2-inch flapper. Do not guess the size. Instead, empty the tank and measure the circumference of the flapper with your tape measure. You’ll know when you purchase your flapper if it is 2 to 3 inches in width.

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