What is the formula for finding weight from density?

First find mass using mass = density x volume (m = rho x V). Then find true weight (a force) using weight = mass x gravity (W = m x g), where g is 9.80665 m/s2 on Earth (local gravity in New Zealand is very close to this standard value, varying slightly with latitude and altitude). Mass is measured in kilograms and stays the same everywhere. Weight is a force measured in newtons and changes with gravity, for example on the Moon weight is about one sixth of the Earth value even though mass is unchanged.

Is weight the same as mass in everyday use?

In everyday NZ usage, 'weight' almost always means mass in kilograms, such as when weighing produce or checking luggage limits. In physics, weight is strictly a force in newtons equal to mass multiplied by gravitational acceleration. This calculator shows both: the mass in kilograms (what a set of kitchen or bathroom scales reads) and the true scientific weight in newtons (the gravitational force acting on that mass).

How do I convert between density units like g/cm3 and kg/m3?

1 g/cm3 equals 1,000 kg/m3, because there are 1,000,000 cm3 in a cubic metre but only 1,000 grams in a kilogram, a factor of 1,000 difference. 1 g/mL equals 1 g/cm3 equals 1 kg/L, since a millilitre and a cubic centimetre are the same volume. This calculator converts your chosen density and volume units automatically before calculating mass and weight.

Density to Weight Calculator

Work out the mass and weight of an object or volume of material from its density. Mass is found using mass = density x volume, and true weight (a force in newtons) is found using weight = mass x gravity.

Choose a material preset or enter a custom density, pick your volume and units, and get mass in kilograms plus weight in newtons instantly.

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Reference constants Standard gravity (9.80665 m/s2) and common material densities at room temperature.

1. Density

Material preset

Density value

kg/m3

Density unit

2. Volume and Gravity

Volume value

vol.

Volume unit

Gravitational acceleration

Mass and Weight

Density (SI)

kg/m3

Volume (SI)

Mass
-
kilograms (kg)

True Weight
-
newtons (N)

Calculation Breakdown

Density entered-

Density converted (SI)-

Volume entered-

Volume converted (SI)-

Mass = density x volume-

Mass-

Weight Conversion

Gravity used-

Weight = mass x gravity-

Weight (newtons)-

Weight in kilograms-force-

Weight in pounds-force-

Result: Enter a density and volume above.

How to Calculate Weight from Density

Density describes how much mass is packed into a given volume. To find the mass of an object or a quantity of material, multiply its density by its volume: mass = density x volume (m = rho x V). To go from mass to true weight, which is a force caused by gravity, multiply mass by gravitational acceleration: weight = mass x gravity (W = m x g). On Earth, standard gravity is 9.80665 metres per second squared, so a 1 kg mass weighs about 9.81 newtons.

Mass vs Weight: What Is the Difference?

Mass and weight are often used interchangeably in everyday NZ conversation, but they are different physical quantities. Mass is the amount of matter in an object, measured in kilograms, and it does not change regardless of location. Weight is the force that gravity exerts on that mass, measured in newtons, and it changes depending on the strength of gravity. A 10 kg block has a mass of 10 kg everywhere in the universe, but its weight is about 98.1 N on Earth, about 16.2 N on the Moon, and about 37.2 N on Mars.

Bathroom scales and kitchen scales are calibrated to show mass in kilograms, even though they technically measure the force you exert on them. This calculator gives you both figures: the mass in kilograms that a set of scales would show, and the scientific weight in newtons.

Common Density Values

Material	Density (kg/m3)
Air (sea level, 15C)	1.225
Pine timber (dry)	600
Water (fresh, 4C)	1,000
Concrete	2,400
Aluminium	2,700
Steel	7,850
Copper	8,940
Lead	11,340

Density and Volume Unit Conversions

1 g/cm3 equals 1,000 kg/m3, since there are 1,000,000 cm3 in a cubic metre but only 1,000 grams in a kilogram. 1 g/mL equals 1 g/cm3 equals 1 kg/L, because a millilitre and a cubic centimetre are the same volume. This calculator automatically converts your chosen density and volume units to the SI base units (kg/m3 and m3) before multiplying them.

Related Calculators

Sources: NIST Special Publication 330, The International System of Units (SI), for the standard gravity constant (9.80665 m/s2). Standard engineering material density references for common materials (water, steel, concrete, aluminium, copper, lead, pine timber, air).

This calculator provides indicative estimates only. Real-world material densities vary with temperature, pressure, moisture content, alloy composition, and manufacturing process. Use manufacturer or laboratory data for engineering or safety-critical calculations.

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