What is specific gravity in pharmacy?

Specific gravity (SG) is the ratio of a liquid's density to the density of water (1 g/mL at 4°C). An SG of 1.2 means the liquid is 1.2 g/mL — 20% denser than water. It is used to convert between volume and mass for liquid preparations.

How do I calculate mass from volume and specific gravity?

Multiply the volume (mL) by the specific gravity to get the mass in grams. For example, 50 mL of glycerin (SG 1.26) weighs 50 × 1.26 = 63 g.

How do I calculate volume from mass and specific gravity?

Divide the mass (g) by the specific gravity to get the volume in mL. For example, 100 g of propylene glycol (SG 1.036) occupies 100 ÷ 1.036 ≈ 96.5 mL.

What are common specific gravity values for pharmacy liquids?

Water: 1.00, ethanol 95%: 0.816, glycerin: 1.26, propylene glycol: 1.036, sorbitol 70%: 1.285, concentrated hydrochloric acid: 1.18. Always verify with the current lot's certificate of analysis.

Why does specific gravity matter in compounding?

Many compounding formulas specify ingredients by weight (grams). If you measure by volume (mL) with a graduated cylinder, you must convert using specific gravity to dispense the correct amount.

Is specific gravity the same as density?

They are numerically equal when density is expressed in g/mL (since water = 1 g/mL). Specific gravity is dimensionless; density carries units. For most pharmacy calculations the values are interchangeable.

Specific Gravity (Pharmacy) Calculator

Name: Specific Gravity (Pharmacy) Calculator
Availability: InStock
Author: Nham Vu

Calculate mass, volume, or density of pharmaceutical liquids using specific gravity — useful for compounding, dispensing, and formulation work.

Calculation Mode

Mass from Volume & SG Volume from Mass & SG Specific Gravity from Mass & Volume

Volume (mL)

Mass (g)

Specific Gravity (g/mL)

Common:

Select a mode and enter values to calculate

Common Pharmaceutical Liquid Specific Gravities

Liquid	SG (g/mL)
Water	1.000
Ethanol 95%	0.816
Isopropyl Alcohol 70%	0.883
Glycerin (Glycerol)	1.260
Propylene Glycol	1.036
Sorbitol Solution 70%	1.285
Mineral Oil (light)	0.860
Castor Oil	0.960
Polyethylene Glycol 400	1.126
HCl (conc. 37%)	1.180

Summary

Calculate mass, volume, or density of pharmaceutical liquids using specific gravity — useful for compounding, dispensing, and formulation work.

How it works

Select the calculation mode: Mass from Volume, Volume from Mass, or Specific Gravity.
Enter the known values in the input fields provided.
Click Calculate to see the result instantly.
Use the Weight per mL panel to confirm the density of your liquid.
Reset the form to start a new calculation.

Use cases

Determine the mass of a measured volume of a pharmaceutical liquid.
Find the volume needed when a prescription specifies a weight of liquid.
Calculate the specific gravity of a liquid from known mass and volume.
Convert between mL and grams for compounding formulations.
Verify concentration or density of liquid preparations.
Adjust volumes when substituting liquids with different specific gravities.
Teaching pharmacy students the relationship between mass, volume, and density.
Cross-check manufacturer specific gravity values during quality control.

Frequently Asked Questions

Last updated: 2026-07-24 · Reviewed by Nham Vu