20 liters in gallons, cups and milliliters

How to convert volume units in 3 steps

Select the source unit, select the target unit, type a number and press Convert. The tool handles 6 units across metric and US imperial systems, covering everything from milliliters to cubic meters.

1

Pick "From unit" - the unit you already have (e.g. US Gallons)

2

Pick "To unit" - what you need (e.g. Liters)

3

Enter the value and hit Convert. The result appears with the exact formula.

Conversion factors - all roads lead to liters

Internally, every input is first converted to liters, then from liters to the target unit. The table below shows how each unit relates to 1 liter:

Unit	Abbreviation	Liters per unit	System
Milliliter	ml	0.001	Metric
Liter	l	1	Metric
Cubic centimeter	cm³	0.001	Metric
Cubic meter	m³	1,000	Metric
US Gallon	gal	3.78541	US Imperial
US Fluid ounce	fl oz	0.0295735	US Imperial

Note: 1 ml = 1 cm³ exactly. They measure the same volume using different naming conventions (liquid vs solid geometry).

Common mistakes to avoid

Mixing US and Imperial gallons. A US gallon is 3.785 liters. A UK (Imperial) gallon is 4.546 liters - about 20% larger. This converter uses US gallons. If you need UK gallons, convert to liters first and divide by 4.546.

Confusing cm³ and ml. They are the same volume - 1 cm³ = 1 ml exactly. The only difference is context: cm³ is used in physics and engineering, ml in cooking and medicine.

Forgetting the cubic in m³. A cubic meter is 1,000 liters, not 1 liter. A cube with 1-meter sides holds a thousand 1-liter bottles. It is a much larger unit than most people expect.

Practical examples

Cooking recipe from the US: "Add 2 cups (16 fl oz) of broth"
16 fl oz = 473.18 ml - roughly half a liter

Car fuel tank: "15-gallon tank, how many liters?"
15 gal = 56.78 liters

Swimming pool volume: "50 m³ pool, how many gallons?"
50 m³ = 50,000 l = 13,209 gal

Medicine dose: "5 ml per dose, how many fluid ounces?"
5 ml = 0.169 fl oz (about 1 teaspoon)

Aquarium: "200-liter tank in gallons"
200 l = 52.83 gal (a standard 55-gallon tank is close)

Engine displacement: "2000 cm³ engine"
2000 cm³ = 2.0 liters - a "two-liter engine"

Quick reference - most common conversions

From	To	Multiply by
Gallons	Liters	3.78541
Liters	Gallons	0.26417
Fluid ounces	Milliliters	29.5735
Milliliters	Fluid ounces	0.03381
Cubic meters	Liters	1,000
Liters	Cubic meters	0.001

FAQ

Is a US gallon the same as a UK gallon?

No. A US gallon = 3.785 liters. A UK (Imperial) gallon = 4.546 liters. The UK gallon is about 20% larger. This converter uses US gallons, which are standard in American recipes, fuel economy ratings and product labels.

What is the difference between cm³ and ml?

None in terms of volume - 1 cm³ = 1 ml exactly. The cubic centimeter (cm³, also written cc) is used in engineering, engine displacement and medical syringes. The milliliter (ml) is preferred in cooking, beverages and pharmaceutical labels.

How many fluid ounces in a liter?

About 33.814 US fluid ounces per liter. A 1-liter water bottle is roughly 34 fl oz. An 8 fl oz glass is about 237 ml, so you get roughly 4.2 glasses per liter.

Why is m³ so much larger than a liter?

A cubic meter is a cube with 1-meter edges - 100 cm on each side. Its volume is 100 x 100 x 100 = 1,000,000 cm³ = 1,000 liters. It is the standard SI unit for large-scale volume measurements like room volume, water tanks and concrete orders.

Can I convert dry volume with this tool?

The units here measure space, not weight, so they work for any substance - liquid or dry. Pour flour into a 250 ml measuring cup and it holds 250 ml of flour. The weight will differ (flour is lighter than water per ml), but the volume is the same.

How accurate is the conversion?

Results are rounded to 4 decimal places. The underlying conversion factors (e.g. 1 gal = 3.78541 l) are the internationally accepted exact or rounded standard values. For everyday use this precision far exceeds what any measuring cup or graduated cylinder can resolve.

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20 liters - how many gallons, cups and ml?

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