Moles to Grams Calculator

Converting moles to grams is essential for preparing solutions and calculating product masses. Multiply moles by molar mass: m = n × M. This is the reverse of the grams-to-moles conversion.

⚗️ Stoichiometry📐 m = n × M🧪 General Chemistry

Amount, n (mol)

Molar mass, M (g/mol)

Enter a non-negative number of moles and a molar mass greater than zero.

Formula & Reference

Variable	Symbol	Formula	Units
Mass	m	m = n × M	g
Moles	n	n = m/M	mol
Molar Mass	M	Sum of atomic masses	g/mol
Example	1 mol NaOH	1 × 40.00 = 40.00 g	g
Example	2.5 mol H₂O	2.5 × 18.02 = 45.05 g	g

Step-by-Step Examples

Example 1

Prepare NaOH Solution

Need 0.500 mol NaOH (M=40.00 g/mol). How many grams to weigh?

m = n × M = 0.500 × 40.00
m = 20.00 g

✓ Weigh out 20.00 g of NaOH

Example 2

Product Mass

A reaction produces 3.00 mol CO₂ (M=44.01 g/mol).

m = 3.00 × 44.01 = 132.03 g

✓ 132.0 g of CO₂ produced

Example 3

Milligram Scale

0.00100 mol of aspirin (M=180.16 g/mol).

m = 0.00100 × 180.16 = 0.180 g = 180 mg

✓ 180 mg of aspirin

Real-World Applications

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Solution Preparation

Calculating grams needed to make molar solutions is the most common lab task.

🏭

Production Scale-Up

Industrial chemists convert mole-based reaction calculations to kilogram quantities.

📊

Yield Calculations

Comparing theoretical yield (g) to actual yield requires moles-to-grams conversion.

💊

Medication Compounding

Pharmacists convert molar doses to gram quantities for compound preparation.

Common Mistakes to Avoid

⚠️

Multiplying instead of dividing (grams to moles)

m = n×M gives grams from moles. n = m/M gives moles from grams. Keep the direction clear.

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Forgetting to look up molar mass

M must be calculated from the formula. Never guess. H₂O=18.02, NaCl=58.44, NaOH=40.00.

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Unit mismatch

If moles are given in mmol, convert to mol first: 250 mmol = 0.250 mol. Then multiply by M.

Frequently Asked Questions

How many grams is 1 mole of common substances? ▾

H₂O: 18.02 g, NaCl: 58.44 g, CO₂: 44.01 g, NaOH: 40.00 g, H₂SO₄: 98.08 g, CaCO₃: 100.09 g, glucose: 180.16 g.

How do I weigh out a precise mole amount? ▾

Calculate m = n×M. Tare the balance with your container. Add solid until the balance reads the calculated mass.

What if I need millimoles? ▾

Convert to moles first: 250 mmol = 0.250 mol. Then m = 0.250 × M. Or: m(mg) = mmol × M.

Why must I be precise with molar mass? ▾

In stoichiometry, a small error in M causes errors in all subsequent calculations. Use 4 significant figures minimum.

Can I use this for gases? ▾

Yes. For an ideal gas at STP: 1 mol = 22.4 L. So if you want 2 mol CO₂: mass = 2×44.01 = 88.02 g. Volume at STP = 2×22.4 = 44.8 L.

Related Chemistry Calculators

Formula Explorer connections

Interpretation: This relationship converts chemical amount, mass, composition or balanced-equation ratios into a reaction quantity. Assumption: Use a balanced reaction, consistent units and the correct molar mass. Purity, side reactions and limiting reagents can change experimental results.

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