GPF vs LPF in Toilets: What Does Each Mean?

GPF and LPF: Two Units for the Same Measurement

GPF stands for gallons per flush. LPF stands for liters per flush. Both describe the volume of water that a toilet releases into the bowl during one flush. The numeric value tells you how much water is used. The only difference is the unit of measurement: gallons are part of the US customary system, while liters are part of the metric system.

In the United States, toilet specifications almost always list GPF. The EPA sets the federal standard for toilet water use at 1.6 gallons per flush, and the WaterSense label certifies toilets that use 1.28 gallons per flush or less. These numbers are useful benchmarks when you shop for a toilet, regardless of whether the spec sheet also gives an LPF figure. According to the EPA, toilets are by far the main source of water use in the home, accounting for nearly 30 percent of an average home's indoor water consumption. The same source notes that older, inefficient toilets can use as much as 6 gallons per flush, so reading flush volume correctly can help you avoid wasting water.

How to Convert Between GPF and LPF

To compare toilets that use different units, you need to know the relationship between gallons and liters. This relationship is a fixed constant, defined by international agreement. To convert a GPF value to LPF, you multiply the GPF number by this constant. To convert the other way, you divide the LPF number by the same constant. You can find the exact factor in any standards handbook or unit conversion tool.

When you see a toilet rated in LPF, you can still evaluate its efficiency without doing a precise conversion. Remember that a liter is a smaller unit than a gallon, so the same volume of water will produce a larger number in liters than in gallons. Therefore, a toilet that uses more than 1.6 gallons per flush will have an LPF rating that is a larger number. Conversely, a toilet that uses 1.28 gallons per flush will have an LPF rating that is also larger than 1.28, but the exact number is not needed for a rough comparison.

Why the Unit Matters When You Buy a Toilet

If you shop for a toilet in the US, you will almost always see GPF. If you buy from an international brand or a listing that includes metric measurements, you might see LPF. Some manufacturers list both units, especially for models sold globally. Knowing both terms helps you avoid misreading a specification. For instance, a toilet labeled with a high LPF number could still use more water than a toilet with a low GPF number, because the numeric relationship is not one-to-one.

The EPA's WaterSense program simplifies this for US buyers. According to the EPA, a WaterSense labeled toilet has been independently certified to meet criteria for both efficiency and performance, and it uses 1.28 gallons per flush or less. If you see the WaterSense label, you know the toilet meets that benchmark regardless of the unit used on the packaging. To learn more about the certification, see our article on WaterSense certification.

Reading Flush Volume Ratings in Practice

Toilet spec sheets typically list flush volume along with other dimensions such as rough-in size and bowl shape. You might see a value like '1.28 GPF' or an equivalent metric value depending on the market. When comparing two toilets, confirm that you are looking at the same unit. If one uses GPF and the other uses LPF, convert using the standard factor before judging which uses less water.

Dual-flush toilets have two flush volumes: a reduced flush for liquid waste and a full flush for solid waste. The reduced flush uses less water, which can save water over time. To understand how dual-flush toilets work, see our explanation of dual-flush mechanisms and browse best dual-flush toilets for examples.

Common Flush Volume Benchmarks

In the US, the federal standard for toilets is 1.6 gallons per flush. According to the EPA, design improvements have allowed toilets to use 1.28 gallons per flush or less while still providing equal or superior performance. This is 20 percent less water than the federal standard. These numbers give you a useful reference when reading a spec sheet in either GPF or LPF.

Older, inefficient toilets used as much as 6 gallons per flush, according to the EPA. Replacing one of these units with a 1.28 GPF WaterSense labeled model can cut toilet water use dramatically. The EPA estimates that replacing old toilets with WaterSense labeled models can reduce water used for toilets by 20 to 60 percent. That context makes the difference between 1.6 and 1.28 GPF feel more meaningful.

Dual-flush models add another layer. A dual-flush toilet has a reduced flush mode for liquid waste and a full flush mode for solid waste. The reduced flush uses less water, and the EPA notes that choosing this mode can save even more water. When you compare a dual-flush model, look at both flush volumes: the lower number applies only to the reduced mode. For help choosing, review our roundup of dual-flush toilets.

Choosing the Right Flush Volume for Your Home

For most households, a toilet with a flush volume at or below the EPA's WaterSense threshold of 1.28 GPF offers a good balance of performance and water savings. If you want maximum efficiency, you can look for models rated even lower, such as those below 1.2 GPF. However, performance also depends on the flush design, not just the water volume. To learn more about flush types, read our article on flush types and our flush volume guide.

The EPA notes that replacing old, inefficient toilets with WaterSense labeled models can reduce water used for toilets by 20 to 60 percent, saving nearly 13,000 gallons a year for the average family. These savings make the effort of comparing GPF and LPF ratings worthwhile. If you want to understand how your household uses water, see our guide to toilet water usage.

When shopping, decide first whether you care more about absolute minimum water use or overall flush performance. A 1.28 GPF model is the most common WaterSense choice and appears in a wide variety of styles. If you prefer a less aggressive flush, a 1.6 GPF model may feel more familiar, while still meeting the federal standard. You can compare models in our best 1.5 to 1.6 GPF toilets guide.

What to pick for your use

Questions

What does GPF stand for?

Gallons per flush. It measures the volume of water a toilet uses in one flush, using US customary units. Most US toilet specs use this rating.

What does LPF stand for?

Liters per flush. It measures the same volume but in metric units. It is common on toilets designed for international markets.

How do I convert GPF to LPF?

Multiply the GPF value by the number of liters in a gallon. The conversion factor is a fixed constant; you can find it in any standard reference. To go the other way, divide the LPF value by the same constant. The exact number isn't necessary for comparing relative efficiency.

Why do some toilets list both GPF and LPF?

Manufacturers that sell in multiple markets often provide both so buyers can read the specification in their preferred unit.

Is a toilet with a lower LPF always more efficient?

The numeric value in LPF is directly comparable to that in GPF once you convert. A lower number, regardless of unit, means less water per flush. However, overall performance also depends on the flush design.