Specific Gravity Weight Formula Explained
Specific gravity connects density and weight in a simple way. Once you know how many times denser than water a substance is, you can compute its weight from a known volume with a single multiplication. This Specific Gravity Weight Calculator turns that relationship into a fast, practical tool for lab work, process engineering, material selection and more.
Because specific gravity is defined relative to water, the key constant is the density of water expressed in grams per cubic centimeter. In metric units, water has a reference density of 1 g/cm³, which greatly simplifies the formula.
Definition Of Specific Gravity
Specific gravity is defined as the ratio between the density of a substance and the density of water at a reference temperature. Let ρmaterial be the density of the material and ρwater the density of water. Specific gravity is:
When densities are expressed in g/cm³, ρwater is taken as 1 g/cm³, so the density of the material is recovered by:
Weight From Specific Gravity And Volume
Weight is density multiplied by volume. If V is volume in cubic centimeters and ρmaterial is in g/cm³, the weight in grams W is:
Substituting the density expression in terms of specific gravity gives:
Using ρwater = 1 g/cm³ and V in cm³ (or mL) simplifies this to the core calculator formula:
This means that for every cubic centimeter of volume, the weight in grams is simply the specific gravity value itself.
Supported Volume Units And Conversions
The calculator accepts four volume units and converts each to cubic centimeters before applying the weight formula:
- Milliliter (mL) – 1 mL = 1 cm³
- Cubic centimeter (cm³) – base unit for the formula
- Liter (L) – 1 L = 1000 cm³
- Cubic inch (in³) – 1 in³ ≈ 16.387064 cm³
If Vinput is the user volume and Vcm³ is the converted volume in cubic centimeters, the weight in grams is always:
Conversions From Grams To Kilograms And Pounds
Once weight is known in grams, it is easy to convert to kilograms and pounds using standard unit relationships:
The Specific Gravity Weight Calculator applies these formulas directly, so you can read off all three units at once.
Worked Example: Liquid With SG = 1.2
Assume a liquid has a specific gravity of 1.2 and you have 250 mL of it. Since 1 mL = 1 cm³, V = 250 cm³. The weight in grams is:
Convert this to kilograms and pounds:
W(lb) = 300 ÷ 453.59237 ≈ 0.661 lb
Entering SG = 1.2 and volume = 250 mL in the calculator will produce the same set of values automatically.
Worked Example: Solid With SG = 7.8
Suppose a metal sample has a specific gravity of 7.8 and volume 10 cm³. The weight in grams is:
Converted to kilograms and pounds:
W(lb) = 78 ÷ 453.59237 ≈ 0.172 lb
How To Use The Specific Gravity Weight Calculator
- Enter the specific gravity of the material. Use a value greater than zero.
- Enter the volume of the material and choose the appropriate unit (mL, cm³, L or in³).
- Select how many decimal places you want in the output.
- Click the calculate button to see the weight in grams, kilograms and pounds.
- Use the results for design calculations, quality checks, batching or shipment estimates.
Why Specific Gravity Is Useful In Practice
Specific gravity lets you convert between volume and weight without having to carry unit-specific density values for every material. Once the SG is known, one formula covers many tasks: sizing storage tanks, computing shipping weights, scaling recipes, or estimating the mass of irregular shapes whose volume can be measured by displacement.
This Specific Gravity Weight Calculator focuses on numeric accuracy and clear formulas, so you can understand each step and trust the results in your engineering or laboratory workflow.
Specific Gravity Weight FAQs
Frequently Asked Questions About Specific Gravity And Weight
Get quick answers about using specific gravity to convert volume into weight in real-world applications.
Yes. As long as you know the specific gravity and volume, the same SG × volume formula applies to liquids, solids and mixtures. The calculator does not depend on whether the material flows or not.
No. You can choose mL, cm³, L or in³ as input volume units. The calculator converts them internally to cubic centimeters before applying the weight formula, so you can work directly with the units most natural to your task.
An SG below 1 means the material is less dense than water. The calculator still uses the same formula and returns a lower weight than an equal volume of water would have.
This calculator is designed to go from SG and volume to weight. For the inverse calculation, you would rearrange the formula to Volume = Weight ÷ (SG × ρwater) and use the units you need.
The precision depends on your application. For rough estimates, SG to one decimal place may be enough. Laboratory or process control work often uses three or four decimal places. The calculator accepts fine precision and rounds the final results to your chosen decimal setting.