Specific Gravity Calculator
Calculate specific gravity calculator calculate relative density SG from substance density and reference fluid density (SG = rho_substance / rho_water). Accurate physics formulas and unit conversions for engineers, students & technicians.
Calculate Specific Gravity (SG = ρ_substance / ρ_ref)
Enter your physical parameters below to compute verified relative density metrics.
Calculation Results
Calculated using verified physical methodology: Specific Gravity: \text{SG} = \frac{\rho_{substance}}{\rho_{ref}}
Submerged Floating Fraction: \frac{V_{submerged}}{V_{total}} = \text{SG} \text{ (if SG} < 1.0)
Quick Summary
The Specific Gravity Calculator evaluates dimensionless relative density ($\text{SG} = \frac{\rho_{substance}}{\rho_{ref}}$) comparing sample density against pure water ($1,000\text{ kg/m}^3$) to predict buoyancy flotation status.
Formula Explanation
Specific Gravity: \text{SG} = \frac{\rho_{substance}}{\rho_{ref}}
Submerged Floating Fraction: \frac{V_{submerged}}{V_{total}} = \text{SG} \text{ (if SG} < 1.0)
How It Works
The Specific Gravity Calculator divides sample density ($\rho_{substance}$) by reference fluid density ($\rho_{ref}$). It outputs Specific Gravity ($\text{SG}$), relative density percentage ($\text{SG} \times 100\%$), water buoyancy status (sinks vs floats), and submerged volume fraction.
Step-by-Step Worked Example
Practical Problem: Calculate Specific Gravity for aluminum metal ($\rho_{substance} = 2,700\text{ kg/m}^3$) relative to pure water ($\rho_{ref} = 1,000\text{ kg/m}^3$).
- Step 1: Identify Input Density Parameters: $\rho_{substance} = 2,700\text{ kg/m}^3$, $\rho_{ref} = 1,000\text{ kg/m}^3$.
- Step 2: Apply the Specific Gravity Formula: $\text{SG} = \frac{\rho_{substance}}{\rho_{ref}}$.
- Step 3: Execute Division for Dimensionless Ratio: $\text{SG} = \2,700 / 1,000 = 2.7000\text{ (dimensionless ratio)}$.
- Step 4: Calculate Relative Density Percentage: Relative Density = $2.70 \times 100\% = 270.00\%$.
- Step 5: Determine Buoyancy Flotation Status: Since $\text{SG} = 2.70 > 1.0$, aluminum is denser than water and will sink rapidly. Density difference $\Delta \rho = +1,700\text{ kg/m}^3$.
Real-World Calculation Examples
Scenario 1: Aluminum Metal Alloy
Parameters: $\rho_{sub} = 2,700\text{ kg/m}^3$, $\rho_{ref} = 1,000\text{ kg/m}^3$
Result: $\text{SG} = 2.70$ ($270\%$). Sinks in water.
Scenario 2: Oak Hardwood Timber Block
Parameters: $\rho_{sub} = 750\text{ kg/m}^3$, $\rho_{ref} = 1,000\text{ kg/m}^3$
Result: $\text{SG} = 0.75$ ($75\%$). Floats in water with $75\%$ volume submerged.
Scenario 3: Crude Petroleum Oil Fuel
Parameters: $\rho_{sub} = 850\text{ kg/m}^3$, $\rho_{ref} = 1,000\text{ kg/m}^3$
Result: $\text{SG} = 0.85$ ($85\%$). Floats on water surface (oil slick).
Scenario 4: Pure Gold Ingot Metal
Parameters: $\rho_{sub} = 19,320\text{ kg/m}^3$, $\rho_{ref} = 1,000\text{ kg/m}^3$
Result: $\text{SG} = 19.32$ ($1,932\%$). Extremely dense metal sinking status.
Key Benefits of Using This Calculator
Flotation & Buoyancy Prediction
Predicts whether materials will float ($\text{SG} < 1.0$) or sink ($\text{SG} > 1.0$) instantly.
Floating Submerged Fraction
Computes submerged volume fraction ($V_{submerged}/V_{total} = \text{SG}$) for floating bodies.
Custom Reference Fluids
Supports custom reference fluids (seawater $1025\text{ kg/m}^3$, air $1.225\text{ kg/m}^3$, mercury $13560\text{ kg/m}^3$).
100% Free & Client-Side
Executes locally in your browser with zero latency or web server transmission.
Frequently Asked Questions (FAQ)
What is Specific Gravity?
Specific Gravity (SG), or relative density, is a dimensionless ratio comparing the density of a substance to a reference fluid (usually water at 4°C for liquids/solids, or air for gases).
What is the formula for Specific Gravity?
SG = rho_substance / rho_reference.
What are the units of Specific Gravity?
Specific Gravity is a pure dimensionless number (ratio with zero physical units).
Why is g/cm³ numerical value identical to Specific Gravity for water?
Because water density is 1.00 g/cm³, dividing any substance density in g/cm³ by 1.00 g/cm³ yields the exact same numerical Specific Gravity value.
How relates Specific Gravity to buoyancy?
An object with SG < 1.0 floats in water; an object with SG > 1.0 sinks; an object with SG = 1.0 has neutral buoyancy.
What portion of an iceberg is underwater?
Ice has SG = 0.917 (rho = 917 kg/m³) relative to seawater (rho = 1025 kg/m³); exactly SG_ice/SG_seawater = 917/1025 = 89.5% of an iceberg is submerged below sea level.
What instrument measures Specific Gravity directly?
A hydrometer or pycnometer measures liquid specific gravity directly via flotation equilibrium depth.
What is API gravity in the oil industry?
API gravity is a specialized inverse non-linear scale derived from Specific Gravity: API = (141.5 / SG) - 131.5.
Does temperature affect Specific Gravity?
Yes, because thermal expansion changes liquid density, standard SG measurements specify temperature conditions (e.g. 60°F/60°F or 20°C/4°C).
What is Specific Gravity of Mercury?
Liquid mercury has SG = 13.56 (rho = 13,560 kg/m³), meaning it is 13.56 times denser than water.