SI Units - Volume

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Volume is the measure of the 3-dimensional space occupied by matter, or enclosed by a surface, measured in cubic units. The SI unit of volume is the cubic meter (m³), which is a derived unit.

• Liter (L) is a special name for the cubic decimeter (dm³). The symbol for the liter is uppercase letter “ell” (L) is preferred to avoid the risk of confusion between the lowercase letter “ell” (l) and the number one (1). The script letter l (l) is not an approved symbol for the liter.
• Milliliter (mL) is a special name for the cubic centimeter (cm³).

Use the visual Liter Cube Model to explore common SI volume units as they increase by powers of ten (from left to right). The smallest cube represents 1 cm³ (or 1 mL). The rod of 10 cubes represents 10 cm³ (or 10 mL). The flat square of 100 cubes represents 100 cm³ (or 100 mL). The large cube of 1 000 small cubes represents 1 000 cm³ (1 dm³ or 1 000 mL or 1 L).

Visualize one cubic decimeter (dm³) or one liter (1 L) as a cube where each side is:

• 100 mm;
• 10 cm;
• 1 dm; or
• 0.1 m.

Visualize one liter (1 L) as:

• 1 m² area that 1 mm deep

A key advantage of the SI is that volume (capacity) is defined the same way for solids, liquids, and gases. The SI uses the same units, like cubic meters (m³) or liters (L) and the simple power of ten. For example, a 10 cm × 10 cm × 10 cm cube has a volume of 1 000 cm or 1 L.

This makes learning and teaching easier because you don’t need to consider if it’s a “dry,” “liquid,” or “fluid” volume measurements. In contrast, non-SI (U.S. customary) measurements use different units for “dry,” “liquid,” or “fluid” volume measurements (like bushels for dry commodities or gallons for liquids). Learn more about Unit Conversion resources.

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Resources for Teachers and Students

Student classroom vocabulary:

• Capacity – The maximum amount that an object can contain measured in cubic units.
  • International System of Units – The dominant measurement system used in science and international commerce, abbreviated SI (from the French Le Système International d’Unités). Also known as the metric system of measurement.
• Liter – A volume measurement unit.
• Measure – To determine the dimension, quantity, or capacity.
• Volume – The measurement of the amount of space occupied inside the three-dimensional space. Measured in cubic units.

Teachers: Top 10 Tips for Teaching the Metric System. (NIST)

Credit: NIST

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