How many cups of water make 1 litre?

January 3, 2026 •

3 min read

One liter of water is equal to exactly 1,000 milliliters, but the number of cups required to make 1 litre depends on which cup standard you are using. This seemingly simple question has a nuanced answer that is crucial for everything from baking and cooking to accurately tracking daily water intake.

Quick Summary

The exact number of cups in one liter varies depending on the measurement system used. A U.S. customary cup yields about 4.23 cups per liter, while a metric cup equals exactly 4 cups. Understanding these differences is key for accurate volume conversions.

Key Points

Measurement Systems Matter: The number of cups in a litre depends on whether you are using the US Customary or Metric system.
US Customary vs. Metric: A US customary cup is 236.59 ml (4.23 cups per litre), while a metric cup is 250 ml (4.0 cups per litre).
Practical Conversion for US Users: For most cooking, 4.25 US cups is a practical estimate for one litre.
For Precision, Use Milliliters: To avoid confusion and ensure accuracy in sensitive recipes or for medical tracking, rely on milliliter measurements.
The Metric System's Logic: One kilogram of water is equal to one litre, a simple relationship that makes metric conversions easy.
Avoid Household Cups: A drinking glass or coffee mug is not a reliable measuring device; use standardized liquid measuring cups for accuracy.
Impact of Imprecise Measurements: Inaccurate cup conversions can lead to inconsistent results in recipes, especially in baking.

Understanding the Differences in Measurement

When asking "how many cups of water make 1 litre," the most important factor is understanding which cup you are referencing. Different regions and contexts use different definitions of a 'cup,' which leads to varying conversion factors.

The US Customary Cup

In the United States, a standard cup is based on the US customary system. This system defines 1 cup as 8 U.S. fluid ounces, which equates to approximately 236.59 milliliters. Using this standard, you'll need approximately 4.2268 US customary cups to make 1 litre. For practical cooking, this is often rounded down to 4.25 cups or simply 'a little over 4 cups.'

The Metric Cup

Many other countries, particularly those that use the metric system, define a cup differently. The metric cup is a standardized 250 milliliters. This makes for a much cleaner conversion: exactly 4 metric cups make 1 litre. This simplified conversion is one of the benefits of using the metric system for volume measurement.

The Imperial Cup

Less commonly used today, the imperial cup was historically used in the British Commonwealth. It defined a cup as 10 imperial fluid ounces (284.13 milliliters). This conversion would require approximately 3.52 imperial cups to make 1 litre.

Comparison Table: Cups per Liter by System

To make it easy to compare, here is a breakdown of the different 'cups' and their relationship to one liter of water.


Measurement System	Cup Volume (ml)	Cups per 1 Litre (Approx.)	Use Case
US Customary	236.59 ml	4.23 cups	US recipes and hydration tracking
Metric	250 ml	4.00 cups	International cooking, metric systems
Imperial	284.13 ml	3.52 cups	Historical, less common today
US 'Legal' Cup	240 ml	4.17 cups	Nutritional labeling in the US

Why Precision Matters in Recipes and Hydration

For most home cooks, the small discrepancy between 4 and 4.23 cups might not make a huge difference, but in baking, where chemical reactions depend on precise ratios, it can affect the outcome. Similarly, if you are strictly tracking your water intake, knowing which cup size you are using is essential for accuracy. Using a standard measuring cup is recommended over a coffee mug or drinking glass, as these can vary widely in volume.

Practical Measurement Tips

Use the Right Tools: Always use a set of standardized measuring cups and a liquid measuring jug with clear markings for the most accurate results.
Read the Recipe: Check if the recipe specifies a measurement system. If it lists ingredients in grams and milliliters, it is likely using the metric system, and 4 cups will equal 1 litre. If it uses ounces and pounds, the US customary system is probably in use.
Think in Milliliters: For ultimate accuracy, use milliliters. Since 1 litre is exactly 1,000 ml, you can easily use measuring tools marked in ml for precise conversions.

How to Measure 1 Litre with US Customary Cups

Here is a simple, step-by-step method to measure out approximately one litre using standard US customary cups:

Take a liquid measuring jug with a capacity of at least one litre.
Fill a 1-cup measuring cup with water and pour it into the jug.
Repeat this process four times, totaling 4 cups or 946.36 ml.
Add a final 1/4 cup (approximately 59 ml) to get very close to the 1,000 ml mark.
For absolute precision, use the milliliter markings on the side of the measuring jug instead of relying on cups.

The Role of Water in the Metric System

The metric system was intentionally designed to be logical and base-10. This is evident in the relationship between volume and weight when measuring water. One litre of water weighs exactly one kilogram at its maximum density (just above freezing point). This simple relationship simplifies many scientific and culinary calculations and is a stark contrast to the more complex conversion factors found in customary systems. For example, 1 cubic centimeter of water weighs 1 gram.

Conclusion

While the simple answer to "how many cups of water make 1 litre?" is a concise "it depends," the details reveal a clear path to accurate measurement. For those using the metric system, the answer is a straightforward 4 cups. For US cooks and hydration trackers, the answer is approximately 4.23 cups. Understanding the difference between these measurement standards is the key to ensuring precision in the kitchen and in tracking your daily water intake. By using the right measuring tools and being aware of the specific standard you're following, you can confidently convert between cups and litres with ease. To explore more about the metric system and its use in daily life, visit the National Institute of Standards and Technology (NIST) website. [https://www.nist.gov/pml/weights-and-measures/metric-si/si-units]

Frequently Asked Questions

No, it depends on the cup size. Four metric cups (250 ml each) make exactly 1 litre. However, four US customary cups (236.59 ml each) only amount to 0.946 litres, which is slightly less than a full litre.

There are approximately 4.2268 US customary cups in 1 litre. For everyday purposes, this is often rounded to 4.23 cups or a little over 4 and 1/4 cups.

Different cup sizes exist because of different systems of measurement. The metric system is used globally for science and most international cooking, while the US Customary system is primarily used in the United States.

Yes, a 'legal' US cup is defined as 240 ml and is used for nutritional labeling purposes, whereas a standard US customary cup is 236.59 ml.

Always use a standard, nested liquid measuring cup with clear markings. If the recipe lists metric units like milliliters (ml), use a metric measuring cup for best results. If it uses customary units like fluid ounces (fl oz), use a US customary measuring cup.

For rough conversions, remember that 1 litre is slightly more than 4 US cups. For precise conversions, multiply the number of litres by 4.23 for US cups or by 4 for metric cups. You can also use an online conversion calculator.

No, for practical purposes, the conversion between cups and litres is a measure of volume and remains the same regardless of the liquid. A litre of water is the same volume as a litre of milk or juice.