What if I have weight instead of density?

If you know the weight of equal volumes of your sample and reference (for example, both measured in mL or L), you can divide those weights to get specific gravity directly. Alternatively, divide each weight by the volume to get densities and then use this calculator.

Do units matter for specific gravity?

Units cancel as long as both sample and reference densities use the same unit (g/cm³, kg/m³, lb/ft³, etc.). If you mix units, the ratio will be incorrect, so always convert to matching units first.

Does temperature affect specific gravity?

Yes. Both sample and reference densities change with temperature, which changes the ratio. Many industries specify a reference temperature (such as 20 °C) and provide tables or formulas for temperature correction. For precise work, use temperature‑corrected densities.

Can I convert SG to Brix, Plato, or concentration?

Not directly with this calculator. Converting SG to Brix, Plato, or specific concentration requires empirical correlations that depend on the particular system (such as wort sugar composition or solution chemistry). Use a brewing or chemistry‑specific tool for those conversions.

Which reference density should I use?

Water at 4 °C is conventionally taken as 1.000 g/cm³ for specific gravity of liquids, but some standards use 20 °C or other conditions. For gases, air may be the reference. Choose the reference that matches your field and use the corresponding density in the reference input.

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Specific Gravity Calculator

Compare the density of a substance to water or another reference substance.

Results

Specific gravity: 1.05

Overview

Specific gravity is a dimensionless way to compare how dense something is relative to a reference substance, usually water. Instead of carrying units like g/cm³ or kg/m³, specific gravity is a pure ratio: how many times heavier or lighter a material is per unit volume compared to the reference.

Brewers use SG to track sugar content and fermentation progress, miners use it to identify minerals, and lab techs use it for quality control and solution prep. This calculator takes your sample density (or weight per equal volume) and divides it by a reference density (often water) to give an instant specific gravity number that you can interpret across many contexts.

Because it’s unitless, SG is easy to compare—but it’s still sensitive to measurement accuracy, temperature, and the homogeneity of your sample.

How to use this calculator

Measure or obtain the density (or weight per unit volume) of your sample. For liquids, this might come from a hydrometer, pycnometer, or lab datasheet.
Measure or look up the density of your reference substance at the same or specified temperature—water is often taken as 1.000 g/cm³.
Enter the sample density (or relative weight) as Substance density and the reference density as Reference density, using the same units for both.
Review the computed specific gravity, which is unitless and expresses how dense your sample is compared to the reference.
Interpret SG > 1 as denser than the reference and SG < 1 as less dense, bearing in mind any temperature corrections you may need.

Inputs explained

Substance density (e.g., g/cm³): The measured density of your sample, in any convenient units such as g/cm³, kg/m³, or lb/ft³. You can also enter relative weight per equal volume if both sample and reference are measured in the same way.
Reference density: The density of your reference material, usually water, in the same units as the sample density. For many calculations, water is treated as 1.000 g/cm³ at a specified standard temperature.

Outputs explained

Specific gravity: A unitless ratio equal to sample density divided by reference density. Values above 1 indicate a denser substance than the reference; values below 1 indicate a less dense substance.

How it works

Specific gravity (SG) is defined as the ratio of the density of a substance to the density of a reference substance at a specified temperature.

In most practical cases, the reference is water, taken as 1.000 g/cm³ at about 4 °C (for liquids) or sometimes at 20 °C, depending on the standard.

The calculator simply divides your sample density by the reference density: SG = ρ_sample ÷ ρ_reference.

If you enter equal‑volume weights instead of densities—for example, the weight of a known volume of your sample and the weight of the same volume of water—the units cancel out the same way, as long as both measurements are taken at comparable temperatures.

Values greater than 1 mean the substance is denser than the reference and will tend to sink in it; values less than 1 mean it is less dense and will tend to float.

Formula

Let ρ_sample = density of sample
Let ρ_reference = density of reference

Specific gravity (SG) = ρ_sample ÷ ρ_reference

When to use it

Brewing and winemaking, where hydrometer or density readings are converted to specific gravity to estimate sugar content and track fermentation (original gravity and final gravity).
Comparing mineral or chemical densities to standard values for identification, quality control, or purity checks in geology and industrial processes.
Evaluating whether an object or material will tend to float or sink in a given fluid by comparing SG to 1.0 for that fluid.
Checking the concentration of industrial solutions (such as acids, brines, or coolant mixtures) where specific gravity correlates with strength.
Teaching and learning density concepts in lab or classroom settings using a common, unitless metric.

Tips & cautions

Always keep units consistent between sample density and reference density. The units themselves cancel out in the ratio, but they must match.
Be mindful of temperature: both sample and reference densities change with temperature, so measurements or tables should be taken or corrected to the same reference temperature.
When using hydrometers or densitometers, note their calibration temperature (often 20 °C/68 °F) and apply manufacturer‑supplied correction tables if your sample is warmer or colder.
For gases, specific gravity is often measured relative to air instead of water; in that case, set the reference density accordingly based on standard conditions.
If your sample is a mixture, emulsion, or suspension, stir gently before measurement to get a representative reading, but be aware that trapped bubbles can distort density measurements.
Does not perform automatic temperature correction or apply specific industry correction tables; you must input already corrected densities when high accuracy is required.
Assumes homogeneous samples and neglects effects from bubbles, stratification, or partial mixing, which can distort measured density.
Does not convert specific gravity directly into composition, Brix, Plato, or other derived scales; separate, domain‑specific correlations are required for that.
Uses a single reference density; specialized applications may require different standards or conditions (for example, petroleum specific gravity at 60/60 °F).
Measurement error in either density input (sample or reference) directly affects the computed specific gravity, so instrument calibration and technique matter.

Worked examples

1.05 g/cm³ wort vs water

Sample density (wort) = 1.05 g/cm³.
Reference density (water) = 1.00 g/cm³.
SG = 1.05 ÷ 1.00 = 1.05.
This might correspond to an original gravity (OG) of about 1.050 in brewing notation.

2.7 g/cm³ aluminum vs water

Sample density (aluminum) ≈ 2.7 g/cm³.
Reference density (water) = 1.00 g/cm³.
SG = 2.7 ÷ 1.0 = 2.7.
Aluminum is 2.7 times denser than water and will sink when placed in it.

Coolant mixture vs water at the same temperature

You measure a coolant mixture’s density at 1.08 g/cm³ using a hydrometer.
Reference water density at the same temperature is treated as 1.00 g/cm³.
SG = 1.08 ÷ 1.00 = 1.08.
You compare SG 1.08 to a manufacturer’s chart to infer approximate coolant concentration.

Deep dive

This specific gravity calculator divides your sample density by a reference density, such as water, to give a unitless SG value you can use across brewing, lab, and engineering applications.

Enter matched‑unit densities for your sample and reference to compare materials, check solution strength, or evaluate buoyancy—just remember that temperature and measurement accuracy affect results.

FAQs

What if I have weight instead of density?: If you know the weight of equal volumes of your sample and reference (for example, both measured in mL or L), you can divide those weights to get specific gravity directly. Alternatively, divide each weight by the volume to get densities and then use this calculator.
Do units matter for specific gravity?: Units cancel as long as both sample and reference densities use the same unit (g/cm³, kg/m³, lb/ft³, etc.). If you mix units, the ratio will be incorrect, so always convert to matching units first.
Does temperature affect specific gravity?: Yes. Both sample and reference densities change with temperature, which changes the ratio. Many industries specify a reference temperature (such as 20 °C) and provide tables or formulas for temperature correction. For precise work, use temperature‑corrected densities.
Can I convert SG to Brix, Plato, or concentration?: Not directly with this calculator. Converting SG to Brix, Plato, or specific concentration requires empirical correlations that depend on the particular system (such as wort sugar composition or solution chemistry). Use a brewing or chemistry‑specific tool for those conversions.
Which reference density should I use?: Water at 4 °C is conventionally taken as 1.000 g/cm³ for specific gravity of liquids, but some standards use 20 °C or other conditions. For gases, air may be the reference. Choose the reference that matches your field and use the corresponding density in the reference input.

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This specific gravity calculator is intended for educational and basic laboratory or engineering estimation only. It assumes accurate, temperature‑appropriate density inputs and does not perform corrections or domain‑specific conversions on your behalf. For critical work—such as process control, regulatory reporting, or scientific research—use calibrated instruments, apply proper temperature corrections, and consult relevant standards or a qualified professional.