Mass Calculator
Convert mass between kilograms, grams, pounds, ounces, and more, or solve the density-volume-mass triangle: enter any two of density, volume, and mass and the tool finds the third, in whatever units you choose, with built-in density presets for common materials.
Mass Unit Converter
Enter a valid number to convert.
Density, Volume and Mass Solver
Enter positive numbers for both known values.
How mass unit conversion works
Formula: value in new unit = value in old unit x (old unit in kg) / (new unit in kg). Every unit on this page is defined by its exact equivalent in kilograms, the SI base unit of mass.
The key exact definition: the international avoirdupois pound is defined as 0.45359237 kg exactly (agreed in 1958), so 1 kg = 1 / 0.45359237 = 2.2046226218 lb. The converter uses that full-precision value, not the rounded 2.2 you see on luggage scales, which is why 70 kg comes out as 154.3236 lb instead of 154.0 lb. Supported units: kilograms, grams, milligrams, metric tons, pounds, ounces, and stone.
The density, volume and mass triangle
Formulas: mass = density x volume (m = rho x V), volume = mass / density (V = m / rho), density = mass / volume (rho = m / V). It is one relationship rearranged three ways. A common memory trick is the triangle: write m at the top and rho and V at the bottom corners, cover the unknown, and the remaining symbols tell you whether to multiply or divide.
The catch is units: the formula only works if density and volume units are compatible. A density in g/cm3 with a volume in litres will silently give a wrong answer unless something converts first. This solver converts both inputs to SI units (kg/m3 and m3) behind the scenes before it multiplies or divides, then converts the answer into whatever output unit you picked. Supported density units: kg/m3, g/cm3, kg/L, g/L, lb/ft3. Supported volume units: m3, cm3, litres, mL, cubic feet, cubic inches, US gallons.
Worked examples, verified against the tool
Solve for mass: density 1 g/cm3, volume 500 cm3. In SI: 1,000 kg/m3 x 0.0005 m3 = 0.5 kg = 500.0000 g, which also equals 1.1023 lb and 17.6370 oz. This matches the old calculator’s answer exactly (it computed 500.00 for the same inputs), with units handled honestly this time.
Solve for volume: mass 1,000 kg, density 1,000 kg/m3 (water). V = 1,000 / 1,000 = 1 m3 = 264.1721 US gallons.
Solve for density: mass 500 g, volume 500 cm3. rho = 500 / 500 = 1 g/cm3 = 62.4280 lb/ft3. Every one of these numbers was produced by running the actual page code in Node.
Mass vs weight: the honest distinction
Mass measures how much matter an object contains; its SI unit is the kilogram. Weight is the force gravity exerts on that mass, measured in newtons: weight = mass x gravity. Your mass is the same on the Moon, but your weight is about one sixth of your Earth weight because lunar gravity is weaker.
In everyday speech the words get mixed up, and bathroom scales are calibrated to display mass (kg or lb) even though they physically measure force. This page treats mass as mass: it converts mass units and solves the density-volume-mass relationship, and it never pretends a kilogram is a force.
Why this beats the other mass calculators
CalculatorSoup’s density calculator solves the triangle with units, but it has no mass unit converter and no material presets, and its result is a single line. calculator.net’s mass calculator only solves for mass and expects SI units from you. The old version of this page was worse than all of them: it multiplied two raw numbers, accepted any units silently, and popped up an alert box on bad input. This rebuild covers the full search intent in one page: a dedicated converter for the popular kg to lb direction, a full triangle solver with automatic SI conversion, typical-density presets for twelve common materials, and a multi-unit readout so one calculation answers several questions.
Frequently asked questions
What is the formula for mass?
Mass = density x volume (m = rho x V). If you know any two of density, volume, and mass, the third follows by rearranging: volume = mass / density, density = mass / volume.
How do you convert kg to lb?
Multiply kilograms by 2.2046226218. The pound is defined as exactly 0.45359237 kg, so the conversion factor is 1 / 0.45359237. For example, 70 kg x 2.2046226218 = 154.3236 lb.
What is the difference between mass and weight?
Mass is the amount of matter in an object (kilograms); weight is the force of gravity on that mass (newtons). Mass is the same everywhere, while weight changes with gravity, which is why you weigh less on the Moon without losing any mass.
What is the density of water?
1,000 kg/m3, which is the same as 1 g/cm3 or 1 kg/L. The material presets on this page are typical values at standard conditions, good for homework and estimates but not a substitute for a measured datasheet value in engineering work.
How do I find volume if I know mass and density?
Use V = m / rho, with matching units. For example, 1,000 kg of water at 1,000 kg/m3 occupies 1 cubic metre, which is 264.1721 US gallons. The solver above does the unit conversion for you.
Which units does the mass converter support?
Kilograms, grams, milligrams, metric tons, pounds, ounces, and stone. The solver additionally handles five density units and seven volume units, converting everything through SI units internally.