Need to calculate mass from volume and density, find a molecular weight from a chemical formula, or convert between units of mass? Use the free mass calculator above to get your result in seconds.
This tool handles three common tasks:
- Volume to mass conversion using density
- Molecular weight and molar mass from a chemical formula
- Exact mass calculation including isotope distribution
Enter your values, pick your units, and the calculator does the rest. Results are estimates for planning, education, and quick reference. They are not a substitute for lab-grade instruments or professional analysis.
Mass Calculator Tool
The mass calculator on this page gives you a fast way to convert between mass, volume, and density, or to look up molecular weight for a chemical compound. It runs entirely in your browser. No sign-up required.
Choose the calculation mode that fits your task:
- Volume and density to mass for physics, engineering, or everyday conversions
- Chemical formula to molecular weight for chemistry coursework, lab prep, or research
- Isotope exact mass for analytical chemistry and mass spectrometry work
Results display instantly. You can switch units (kilograms, grams, pounds, ounces) without re-entering your data.
How to Use the Mass Calculator
Enter a Chemical Formula
To find the molecular weight or molar mass of a compound, type its molecular formula into the formula field. Use standard notation:
- H2O for water
- C6H12O6 for glucose
- NaCl for sodium chloride
Capitalize element symbols correctly. The first letter is uppercase, the second (if any) is lowercase. "Co" means cobalt. "CO" means carbon and oxygen.
The calculator reads each element symbol, multiplies by the subscript number, and sums the atomic mass values. If your formula includes a molecule of crystallization or a hydrate (like CuSO4·5H2O), enter the full formula including the water molecules.
Enter Volume and Density
To calculate mass from volume and density, enter two values:
- Volume of the substance (liters, milliliters, cubic meters, cubic centimeters, gallons, etc.)
- Density of the substance (grams per cubic centimeter, kilograms per cubic meter, pounds per gallon, etc.)
The tool multiplies volume by density to return mass in your chosen unit. If you already know mass and volume but need density, or you know mass and density but need volume, the calculator can solve for the missing value.
Volume to Mass Calculator
Volume to Mass Formula
The core formula is straightforward:
Mass = Volume × Density
- Mass is the amount of matter in an object, measured in grams, kilograms, or pounds.
- Volume is the space the object occupies, measured in liters, milliliters, or cubic meters.
- Density is mass per unit of volume, such as grams per cubic centimeter or kilograms per cubic meter.
Rearranging gives you the related formulas:
- Volume = Mass ÷ Density
- Density = Mass ÷ Volume
So if you want to know how to find volume with density and mass, just divide mass by density.
How the Volume to Mass Calculator Uses Density
Density is the bridge between volume and mass. Every substance has a characteristic density under standard conditions.
Water, for example, has a density of about 1 gram per cubic centimeter at room temperature. So 500 mL of water has a mass of roughly 500 grams. Air is far less dense (about 1.225 kg per cubic meter at sea level). Ten grams of air occupies roughly 8.16 liters.
The calculator uses the density value you enter. For common substances, you can look up published density values. For mixtures or non-standard conditions (high temperature, high pressure), density changes, so use a value that matches your actual conditions.
Keep your units consistent. If density is in grams per cubic centimeter, volume should be in cubic centimeters. The calculator handles unit conversion automatically when you select from the dropdown menus.
Molecular Mass Calculator
Molecular Formula and Molar Mass
Molar mass is the mass of one mole (6.022 × 10²³ particles) of a substance. It is expressed in grams per mole (g/mol).
Enter a molecular formula and the calculator sums the atomic masses of every atom in the molecule. For water (H2O), that is:
- Hydrogen: 1.008 g/mol × 2 = 2.016 g/mol
- Oxygen: 15.999 g/mol × 1 = 15.999 g/mol
- Total molar mass: 18.015 g/mol
This value is essential for converting between grams and moles in chemistry calculations. It is based on standard atomic weights, which reflect the natural isotopic distribution of each element.
Molecular Weight and Chemical Composition
Molecular weight and molar mass are often used interchangeably in practice. Technically, molecular weight is a dimensionless ratio comparing a molecule's mass to 1/12 of a carbon-12 atom. The numerical value is the same as molar mass in g/mol.
The calculator also displays the chemical composition of a compound as a percentage by mass. For each element, it divides that element's total atomic mass contribution by the compound's molecular weight, then multiplies by 100.
This breakdown is useful for:
- Verifying empirical formulas
- Checking purity expectations
- Understanding which element dominates a compound's mass
Chemical Formula and Isotope Exact Mass Calculator
Standard molecular weight uses average atomic masses. These averages account for all naturally abundant isotopes of each element.
Exact mass (monoisotopic mass) uses only the most abundant isotope of each element. This is the value mass spectrometry instruments detect as the strongest peak.
For example, the average molecular weight of bromine (Br) is 79.904 g/mol because natural bromine is roughly half ⁷⁹Br and half ⁸¹Br. The exact mass uses ⁷⁸.918 (the most abundant isotope, ⁷⁹Br).
Use the isotope exact mass calculator when you need to:
- Predict or interpret mass spectrometry data
- Distinguish between compounds with very similar average masses
- Confirm molecular identity in analytical chemistry
The calculator references current isotopic mass data for each element. Results are precise to several decimal places, matching the resolution needed for modern analytical instruments.
Mass vs. Weight
Mass and weight are related but not the same property.
- Mass is the amount of matter in an object. It stays constant regardless of location. The SI unit of mass is the kilogram.
- Weight is the gravitational force acting on that mass. It changes depending on where you are. Weight equals mass times gravitational acceleration (W = m × g).
On Earth's surface, g is approximately 9.81 m/s². A 10 kg object weighs about 98.1 newtons here. On the Moon, the same object still has 10 kg of mass but weighs only about 16.3 newtons.
In everyday language, people say "weight" when they mean mass. Bathroom scales display kilograms or pounds, but they are technically measuring the force of gravity on your body and converting it to a mass reading. For most practical purposes on Earth, the distinction does not change your result. In science and engineering, using the correct term matters.
What the Mass Calculator Results Estimate for the User
This mass calculator gives you fast, reliable estimates for common tasks:
- Volume to mass conversions for any substance when you know its density
- Molecular weight and molar mass from a typed chemical formula
- Isotope exact mass for analytical chemistry applications
- Chemical composition as element percentages by mass
Results are based on published atomic mass data, standard formulas, and the values you enter. They are accurate for educational use, quick lab estimates, and everyday planning.
Keep these limitations in mind:
- Density values vary with temperature, pressure, and purity. Use a density that matches your real conditions.
- Atomic mass values reflect internationally accepted averages. Highly specialized research may require primary reference data.
- The calculator does not account for measurement error in your inputs. Your result is only as good as the numbers you provide.
For critical applications (pharmaceutical dosing, regulatory compliance, structural engineering), confirm results with calibrated instruments or a qualified professional.