Molarity Calculator · Practical guide
How to Make a 1 Molar Solution
Weigh the molecular weight in grams, dissolve, and dilute to exactly one liter.
At a glance
The Short Answer
A 1 molar (1 M) solution contains exactly one mole of solute per liter of solution, so for one liter you weigh out the solute's molecular weight in grams: grams = 1 mol/L × volume (L) × molecular weight (g/mol). For NaCl that is 58.44 g per liter; for a different volume, multiply accordingly — 500 mL of 1 M NaCl needs 29.22 g.
Interactive tool
Molarity Calculator
Enter your own values, then compare the result with the examples below.
Results
Grams Needed for 1 Liter of 1 M Solution
| Solute | Molecular Weight (g/mol) | Grams for 1 L of 1 M | Grams for 500 mL |
|---|---|---|---|
| NaCl | 58.44 | 58.44 g | 29.22 g |
| KCl | 74.55 | 74.55 g | 37.27 g |
| NaOH | 40.00 | 40.00 g | 20.00 g |
| Glucose (C6H12O6) | 180.16 | 180.16 g | 90.08 g |
The Correct Technique
- Weigh the calculated mass of solute.
- Dissolve it in less than the final volume of solvent — about 700–800 mL for a 1 L target.
- Transfer to a volumetric flask and add solvent up to the 1 L mark, then mix thoroughly.
Never add a full liter of water to the solute: dissolving changes the total volume, so the final concentration would drift below 1 M. Molarity is defined per liter of final solution, not per liter of solvent.
Scaling to Other Concentrations
The same formula handles any target. A 0.5 M NaCl solution in 250 mL needs 0.5 × 0.25 × 58.44 = 7.305 g; a 2 M glucose solution in 1 L needs 2 × 1 × 180.16 = 360.32 g. Enter your target molarity, volume, and molecular weight in the calculator above to get the required mass instantly.
Frequently Asked Questions
Can I just add one liter of water to the solute?
No. Adding exactly 1 L of solvent ignores the volume change caused by dissolving. Dissolve first in less solvent, then dilute to a final total volume of 1 L.
How much NaCl do I need for 100 mL of 1 M solution?
1 mol/L × 0.1 L × 58.44 g/mol = 5.844 g of NaCl, diluted to a final volume of 100 mL.
What if my solute is a hydrate, like CuSO4·5H2O?
Use the molecular weight of the hydrate, including the water molecules, since that is what you actually weigh out.
Does a 1 M solution mean 1 mole of particles?
Not exactly. A salt like NaCl dissociates into two ions, so 1 M NaCl is about 2 osmoles per liter of dissolved particles, which matters for tonicity calculations.