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Specific Gravity to kg/m³

1 Specific Gravity (SG) = 1,000Kilogram per Cubic Meter (kg/m³)

By KAMP Inc. / UnitOwl · Last reviewed:

Result
1,000 kg/m³
1 SG = 1,000 kg/m³
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How Many kg/m³ for a Given Specific Gravity?

Specific gravity (SG) converts to kg/m³ by multiplying by 1,000. A specific gravity of 1.0 equals 1,000 kg/m³ (the density of water). Specific gravity is a dimensionless ratio — it expresses how many times denser a substance is compared to water at 4°C. An SG of 2.5 means the substance is 2.5 times denser than water, giving a density of 2,500 kg/m³. This conversion is essential in geology (mineral identification), petroleum engineering (crude oil classification), brewing (wort gravity monitoring), and materials science. Because specific gravity has no units, it serves as a universal bridge between density systems — once you know SG, you can convert to any density unit by multiplying by water's density in that unit system. That makes it especially useful when one source reports a dimensionless SG number but the downstream equation, simulator, or engineering spec requires an actual density unit such as kg/m³. It is a simple conversion, but you still need to pay attention to the reference temperature and to whether the reported value is truly SG or a related industry scale.

How to Convert Specific Gravity to Kilogram per Cubic Meter

  1. Start with your specific gravity value.
  2. Multiply by 1,000 to get density in kg/m³.
  3. For example, SG 2.65 x 1,000 = 2,650 kg/m³ (quartz sand density).
  4. To get g/cm³ instead, the specific gravity value IS the g/cm³ value (numerically identical).
  5. To get lb/ft³, multiply SG by 62.428.

Real-World Examples

Crude oil has an SG of 0.87. What is its density in kg/m³?
0.87 x 1,000 = 870 kg/m³. This is a medium-weight crude oil.
A mineral sample has SG 3.2. Express density in kg/m³.
3.2 x 1,000 = 3,200 kg/m³. This density is consistent with minerals like apatite or fluorite.
A brewer measures wort at SG 1.050. What is its density in kg/m³?
1.050 x 1,000 = 1,050 kg/m³. This wort is 5% denser than water due to dissolved sugars.
Battery electrolyte (sulfuric acid solution) has SG 1.28. Convert to kg/m³.
1.28 x 1,000 = 1,280 kg/m³. A fully charged lead-acid battery has electrolyte SG between 1.25-1.30.
Balsa wood has SG 0.12. What is its density in kg/m³?
0.12 x 1,000 = 120 kg/m³. Balsa is one of the lightest commercial woods, about 8 times less dense than water.

Quick Reference

Specific Gravity (SG)Kilogram per Cubic Meter (kg/m³)
11,000
22,000
55,000
1010,000
2525,000
5050,000
100100,000
500500,000
1,0001,000,000

History of Specific Gravity and Kilogram per Cubic Meter

Specific gravity has been used as a material identification tool since antiquity. Archimedes' famous "Eureka" moment around 250 BC involved comparing the specific gravity of a crown to that of pure gold to detect fraud. The concept was formalized in the 17th century when hydrometry became a scientific discipline. Hydrometers — instruments that float at different levels depending on liquid density — measure specific gravity directly and have been used for centuries in brewing, winemaking, and industrial chemistry. The petroleum industry uses a related scale called API gravity (developed by the American Petroleum Institute), where API = (141.5 / SG) - 131.5. Light crude oil has high API gravity (above 31.1°) and low SG, while heavy crude has low API and high SG. Despite the existence of more precise density units, specific gravity persists because of its intuitive meaning: "how many times heavier than water."

Common Mistakes to Avoid

  • Confusing specific gravity with density. SG is dimensionless (no units), while density has units (kg/m³, g/cm³, lb/ft³). An SG of 2.5 is not "2.5 kg/m³" — it is 2,500 kg/m³ or 2.5 g/cm³.
  • Forgetting that SG depends on the reference temperature. Standard SG is referenced to water at 4°C (maximum density). Some industries use water at 15.6°C (60°F) or 20°C as reference, which slightly changes the conversion. The difference is small (less than 0.4%) but can matter for precision work.
  • Assuming SG applies only to liquids. Specific gravity is used for solids (minerals, metals, wood), liquids (fuels, chemicals, beverages), and even gases (referenced to air instead of water).
  • Mixing SG up with related scales such as API gravity, Brix, Plato, or Baumé. Those scales can be derived from density, but they are not the same number as SG. Convert the scale properly first, then multiply by 1,000 if you need kg/m³.
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Frequently Asked Questions

How is specific gravity measured?
For liquids: a hydrometer (floating glass instrument) or digital density meter. For solids: weigh in air and then suspended in water (Archimedes method), or use a pycnometer. For gases: compare to air under the same conditions. Digital density meters using oscillating U-tube technology are the modern standard for precise measurements.
What specific gravity indicates whether something floats or sinks?
Any substance with SG less than 1.0 floats in fresh water. SG exactly 1.0 is neutrally buoyant. SG greater than 1.0 sinks. In seawater (SG about 1.025), objects up to SG 1.025 will float. This is why ships ride higher in salt water than fresh water.
How do brewers use specific gravity?
Brewers measure the SG of wort (unfermented beer) before fermentation (Original Gravity, typically 1.040-1.090) and after (Final Gravity, typically 1.008-1.015). The difference indicates how much sugar was converted to alcohol. Alcohol by volume is approximately: ABV = (OG - FG) x 131.25.
Can I treat SG and g/cm³ as the same number?
Numerically, yes for many practical purposes, because water is about 1.0 g/cm³. Conceptually, no: SG is a ratio with no units, while g/cm³ is a density unit. That distinction matters when you are documenting results, comparing test methods, or feeding values into software that expects a specific unit.
Why do some SG readings look like 1.050 instead of 1.05?
Industries such as brewing often keep three decimal places because small differences are meaningful. An SG of 1.050 equals 1,050 kg/m³, while 1.005 equals 1,005 kg/m³. Writing the trailing zeroes helps show the intended precision of the measurement.
Quick Tip

Specific gravity is the universal density Rosetta Stone. Once you know SG, convert to any density unit: multiply by 1,000 for kg/m³, use the value directly for g/cm³ or kg/L, multiply by 62.4 for lb/ft³, or multiply by 0.0361 for lb/in³. Memorizing water's density in each system is all you need.

Sources & References