Quick answer
Specific gravity is the density relative to water: SG = ρ ÷ 1,000 kg/m³. Steel at 7,850 kg/m³ has an SG of 7.85, so it does not float.
Enter a density in kg/m³. The calculator returns the specific gravity and whether it floats in water.
Related tools: Reynolds Number Calculator: Reynolds number and flow regime in a pipe. Flow Rate Calculator: Volumetric flow rate from area and velocity, or volume and time. Water Viscosity Calculator: Dynamic viscosity of liquid water at a temperature.
How to use the Specific Gravity Calculator
- Enter density (kg/m³) (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Density | A number, in kg/m³ | > 0 |
Formula and method
Formula
SG = ρ ÷ 1,000 kg/m³
IEEE-754 double precision; shown to the decimals indicated.
Reference density is taken as 1,000 kg/m³ (water near 4 °C).
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Density = 7850.
| Result | Value |
|---|---|
| Specific gravity | 7.85 |
| Floats in water? | No |
Example 2
Inputs: Density = 920.
| Result | Value |
|---|---|
| Specific gravity | 0.92 |
| Floats in water? | Yes |
Example 3
Inputs: Density = 1000.
| Result | Value |
|---|---|
| Specific gravity | 1 |
| Floats in water? | No |
The first line is the headline result (specific gravity). Below it the specific Gravity Calculator lists floats in water?, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Floating rule
An object floats in water if its SG is below 1. Ice has an SG of about 0.917, so it floats with 92% below the surface. Seawater is about 1.025.
Temperature
Compare at the same temperature, since water density peaks at 4 °C. SG has no units. Hydrometers measure SG for brewing, batteries and urine tests.
How the result changes with density
Holding every other input at the first worked example, this table changes only density. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Density | Specific gravity | Floats in water? |
|---|---|---|
| 3925 | 3.925 | No |
| 7850 | 7.85 | No |
| 15700 | 15.7 | No |
| 31400 | 31.4 | No |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Density: entering "0" shows "Density must be greater than 0." beside that field and no result.
Choosing between the Specific Gravity Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Reynolds Number Calculator](/science/reynolds-number-calculator/) | fluid density, flow velocity and pipe diameter | Reynolds number |
| [Flow Rate Calculator](/science/flow-rate-calculator/) | use | Flow rate |
| [Water Viscosity Calculator](/science/water-viscosity/) | temperature | Dynamic viscosity |
| [Water Velocity Calculator](/science/water-velocity-calculator/) | flow and inside diameter | Velocity |
| [Pressure Calculator](/science/pressure-calculator/) | force and area | Pressure |
Background: fluid flow
Volumetric flow rate is Q = A × v (cross-sectional area times average velocity). Bernoulli's equation, P + ½ρv² + ρgh = constant, holds along a streamline for steady, incompressible, frictionless flow, so real pipes need friction corrections. The Reynolds number Re = ρvL/μ compares inertia with viscosity.
Laminar flow in a pipe is usually quoted below Re of about 2,100 to 2,300 and fully turbulent above about 4,000, with an uncertain transition between; treat the thresholds as approximate.
Assumptions and limitations
- Compare at the same temperature
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for density to confirm this.
Frequently asked questions
What is the SG of mercury?
Mercury has a specific gravity of about 13.6, so a cubic metre weighs about 13,600 kg.
What is SG for water?
Water has a specific gravity of 1.0 by definition at about 4 °C (1,000 kg/m³).
How do I get density from SG?
Multiply by 1,000 kg/m³.
What does the Specific Gravity Calculator calculate?
Specific gravity from density, relative to water at 1,000 kg/m³. It returns Specific gravity and Floats in water?.
What formula does the Specific Gravity Calculator use?
SG = ρ ÷ 1,000 kg/m³. Reference density is taken as 1,000 kg/m³ (water near 4 °C).
What do I need to enter in the specific Gravity Calculator?
You enter Density (kg/m³).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Compare at the same temperature.
What is an example of a specific Gravity result?
With density 7850, the specific gravity is 7.85.
Where does the method come from?
The method follows: OpenStax, Chemistry 2e (Rice University).
Related calculators
- Reynolds Number Calculator — Reynolds number and flow regime in a pipe.
- Flow Rate Calculator — Volumetric flow rate from area and velocity, or volume and time.
- Water Viscosity Calculator — Dynamic viscosity of liquid water at a temperature.
- Water Velocity Calculator — Water velocity in a pipe from flow and inside diameter.
- Pressure Calculator — Pressure from force and area, with unit conversions.
- Buoyant Force Calculator — Upward buoyant force on a submerged object (Archimedes' principle).
Sources
- OpenStax, Chemistry 2e (Rice University)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.