Calculate mass from amount of substance
Use a molecular formula or provide a trusted molar mass.
Formula used
First, convert the supplied amount into moles. Then multiply moles by the molar mass in grams per mole.
For impure material, required sample mass = pure mass ÷ (purity ÷ 100).
How to use this calculator
- Enter the amount of substance and select its unit.
- Choose formula mode or manual molar-mass mode.
- Type a valid formula, or enter a known molar mass.
- Set purity, output unit, and decimal precision.
- Press Convert to Mass. Review the result above the form.
Example conversions
| Amount | Formula | Molar mass | Mass result |
|---|---|---|---|
| 2 mol | H₂O | 18.015 g/mol | 36.030 g |
| 250 mmol | NaCl | 58.440 g/mol | 14.610 g |
| 15 µmol | C₆H₁₂O₆ | 180.156 g/mol | 2.702 mg |
Molar to Mass Conversion Guide
Moles describe an amount of substance. Mass describes how heavy that substance is. Chemistry problems often require moving between these two measurements. The bridge is molar mass. Molar mass tells you the mass of one mole. It is usually written in grams per mole.
A chemical formula can supply the molar mass automatically. The calculator reads each element symbol. It adds the atomic masses after applying subscripts. For example, water contains two hydrogen atoms and one oxygen atom. Its molar mass is about 18.015 grams per mole. One mole of water therefore has that mass.
Unit choices matter during every conversion. A millimole is one thousandth of a mole. A micromole is one millionth of a mole. The calculator first converts the entered amount to moles. It then applies the mass formula. Finally, it converts the result into your selected output unit. This process reduces manual steps.
Formula mode is useful for common compounds. Enter H2O, NaCl, Ca(OH)2, or CuSO4·5H2O. Parentheses and hydrate dots are supported. Check the formula before calculating. An incorrect subscript changes the molar mass. It can also change the final mass by a lot.
Manual molar-mass mode helps with polymers, mixtures, proteins, and verified reference values. Enter the value and its unit. The calculator normalizes the value to grams per mole. This keeps the calculation consistent. Use a trusted specification when working with specialized materials.
Purity is important when weighing real samples. Pure mass is the exact amount of active substance needed. A sample with lower purity requires more total material. For example, a 90 percent sample needs more mass than a pure sample. The calculator shows both values clearly.
Choose enough decimal places for your work. Educational examples may use three or four places. Sensitive laboratory work may need more. Do not report more precision than your input supports. Balance capacity and measurement uncertainty also limit meaningful digits.
Temperature does not change the basic mole to mass equation. It can still affect how materials are handled. Hygroscopic powders can absorb water. Volatile liquids can lose material during transfer. Record conditions when accuracy matters. Dry glassware, balances, and closed containers improve consistency.
Large batches need practical rounding. Calculate a precise target first. Then compare it with balance readability. A balance reading to 0.01 gram cannot confirm microgram differences. Scale the method or select equipment. Keep units in laboratory notes. This makes later checks easier.
For solution preparation, calculate the solute mass first. Then choose the volume and solvent carefully. Do not confuse moles with molarity. Molarity requires volume as well as amount. The tool converts amount to mass. A separate concentration calculation may be needed afterward.
Use the calculation as a planning aid. Confirm units before weighing materials. Review safety data and procedures separately. This converter handles quantities, not chemical hazards. Good documentation makes experimental preparation easier to repeat and verify.
Frequently asked questions
1. What is molar mass?
Molar mass is the mass of one mole of a substance. It is usually expressed as grams per mole. Formula mode calculates it from standard atomic masses.
2. Can I convert millimoles to milligrams?
Yes. Enter the amount in mmol, select mg as the output unit, and provide a formula or molar mass. The calculator handles the internal unit conversion.
3. Does the calculator support hydrate formulas?
Yes. Enter hydrate formulas using a dot, such as CuSO4·5H2O. The hydrate coefficient is included when the molar mass is calculated.
4. Why is purity included?
Purity adjusts the required weighing amount. A less pure sample contains less active compound per gram. The tool reports the total sample mass needed to obtain the chosen pure mass.
5. What formula does the calculator use?
It uses mass = moles × molar mass. When purity is below 100 percent, it divides pure mass by the purity fraction to find the required sample mass.
6. Can I enter a manual molar mass?
Yes. Select manual molar mass, enter a positive value, and choose its unit. This option is useful when a supplier provides a verified value.
7. Which output mass units are available?
You can display results in grams, kilograms, milligrams, micrograms, nanograms, pounds, or ounces. Select the unit before submitting the conversion.
8. Does the formula reader handle brackets?
Yes. It supports parentheses and square brackets for grouped atoms. Make sure every opening bracket has a matching closing bracket.
9. What should I enter for an impure sample?
Enter the measured purity percentage from your certificate or label. For example, use 95 for a sample that is 95 percent pure.
10. Can I download my calculation?
Yes. After a successful conversion, choose Download CSV. You can also use Print or Save PDF for a clean report.
11. Is this tool suitable for safety decisions?
No. It supports quantity calculations only. Always check safety data, laboratory procedures, concentrations, compatibility, and supervision requirements before handling chemicals.