Density to Specific Gravity
Precise conversions for engineering, labs, and materials analysis
Quick Converter
Popular Conversions
| Material | Density (kg/m³) | Specific Gravity |
|---|---|---|
| Water (4°C) | 1000 | 1.000 |
| Mercury | 13560 | 13.56 |
| Air (STP) | 1.29 | 0.00129 |
| Gasoline | 720 | 0.72 |
| Battery Acid | 1280 | 1.28 |
| Steel | 7850 | 7.85 |
| Gold | 19300 | 19.3 |
Conversion Formula
Specific Gravity (SG) = Density / Reference Density
Reference (water at 4°C) = 999.972 kg/m³ ≈ 1000 kg/m³
Steps:
1. Select input density unit.
2. Enter value.
3. Divide by water density in same unit (e.g., 1 g/cm³ for water).
4. Result is dimensionless SG.
Reference (water at 4°C) = 999.972 kg/m³ ≈ 1000 kg/m³
Steps:
1. Select input density unit.
2. Enter value.
3. Divide by water density in same unit (e.g., 1 g/cm³ for water).
4. Result is dimensionless SG.
Visual Comparison
Real-World Examples
Hydrometers
Measure SG directly in liquids like battery electrolyte (1.26-1.30 for charged).
Urine Tests
Normal range 1.002-1.030; used in clinical hydration assessment.
US vs Metric
US oilfield uses lb/gal (ppg); 8.33 ppg ≈ SG 1.0 for water.
Gemology
Diamonds SG 3.52; distinguishes from glass (2.5) via immersion.
Frequently Asked Questions
What reference temperature for water?
Standard is 4°C (999.972 kg/m³); some use 20°C (998.2 kg/m³) or 60°F (0.999 kg/L).
Is specific gravity unitless?
Yes, dimensionless ratio. No units needed in output.
How does temperature affect SG?
Density changes ~0.02% per °C for water; correct using expansion coefficients.
SG for gases?
Relative to air (1.29 kg/m³ at STP) or hydrogen; e.g., helium 0.1786.
Convert lb/gal to SG?
SG = ppg / 8.33 (water at 60°F).
References
Sensors One. Density to Specific Gravity Calculator. https://www.sensorsone.com/density-to-specific-gravity-calculator/
Omni Calculator. Specific Gravity Calculator. https://www.omnicalculator.com/physics/specific-gravity
Gordon England. Density Unit Converter. https://www.gordonengland.co.uk/conversion/density.htm
Edren, S. Urine Specific Gravity. Journal of Clinical Pathology, 2005.
API RP 10B-2. Recommended Practice for Testing Well Cements, American Petroleum Institute, 2013.
Omni Calculator. Specific Gravity Calculator. https://www.omnicalculator.com/physics/specific-gravity
Gordon England. Density Unit Converter. https://www.gordonengland.co.uk/conversion/density.htm
Edren, S. Urine Specific Gravity. Journal of Clinical Pathology, 2005.
API RP 10B-2. Recommended Practice for Testing Well Cements, American Petroleum Institute, 2013.