Specific Weight Calculator
Enter a density and the local gravity to get the specific weight (weight density) in newtons per cubic metre — and see how it differs from density and specific gravity.
Density times gravity
Enter the density and the gravitational acceleration and this specific weight calculator returns the weight density (γ = ρ·g) in N/m³.
Use SI units
Density in kilograms per cubic metre and gravity in metres per second squared give specific weight in newtons per cubic metre.
What is specific weight?
The weight of a material per unit volume
A specific weight calculator turns two measurements — the density of a material and the local gravitational acceleration — into its specific weight, also called weight density. Specific weight is the weight of a material per unit of volume, measured in newtons per cubic metre (N/m³). It answers a different question from density: density (ρ) is how much mass sits in a cubic metre, while specific weight (γ) is how much that mass actually weighs under gravity. The two are linked by a single multiplication, γ = ρ·g, so the specific weight of fresh water on Earth comes out at roughly 9806.65 N/m³. Engineers reach for it constantly — in hydrostatic pressure, buoyancy, soil mechanics, and structural load calculations — because it converts a volume of material straight into a force.
Enter a density in kilograms per cubic metre and the local gravity in metres per second squared to get the specific weight in newtons per cubic metre instantly.
Specific weight is simply the density multiplied by the local gravitational acceleration.
γ = ρ × gTake fresh water as the worked example: its density ρ is 1000 kg/m³, and on Earth the standard gravitational acceleration g is 9.80665 m/s². Multiplying the two gives 1000 × 9.80665 = 9806.65 N/m³. Keep the units consistent — kilograms per cubic metre for density and metres per second squared for gravity — and the result is always in newtons per cubic metre. Because gravity is a factor, the same material has a different specific weight on the Moon (g ≈ 1.62 m/s²) than on Earth, even though its density never changes.
The formula is exact, but a few practical points are worth keeping in mind.
Not the same as density or specific gravity
Specific weight (γ, in N/m³) is not the same as density (ρ, in kg/m³, a measure of mass per volume) or specific gravity (a dimensionless ratio comparing a material to water). This calculator gives weight density only and assumes a single, uniform value of gravity. Keep your units consistent — kilograms per cubic metre for density and metres per second squared for gravity — or the newtons per cubic metre will be wrong.