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Concentration Calculator

Chemistry

Calculate the concentration of a solution in mol/L from solute mass, molar mass, and solution volume. Also find grams needed for a target molarity.

5.85 g
g
58.44 g/mol
g/mol
0.1 L
L

Molarity (mol/L)

1.001
Moles of Solute
0.1
Mass per Litre (g/L)
58.5

This calculator computes your Molarity (mol/L), Moles of Solute, Mass per Litre (g/L) from the values you enter.

Inputs
Mass of SoluteMolar Mass of SoluteVolume of Solution
Outputs
Molarity (mol/L)Moles of SoluteMass per Litre (g/L)

What is a Concentration?

The Concentration Calculator computes the molarity of a solution from the mass of solute, molar mass of the solute, and volume of the solution. It applies the formula C = n/V where n = mass/M_r, returning molarity (mol/L), moles of solute, and mass concentration (g/L) — the three most commonly needed forms of concentration in a single calculation.

Concentration is the most fundamental property of any solution. It determines how reactive a solution is, how it behaves in titrations, how it interacts with biological systems, and how to prepare it reproducibly. Molarity — moles of solute per litre of solution — is the standard unit in quantitative chemistry because it directly connects to stoichiometry: if a reaction requires one mole of HCl per mole of NaOH, a 1 M HCl solution contains exactly the same reactive quantity as a 1 M NaOH solution, regardless of the very different masses involved (36.46 g vs 40.00 g).

Preparing solutions of known concentration is one of the most frequent tasks in any chemistry laboratory. In India, this is covered in NCERT Class 12 Chemistry Chapter 2 and is a standard practical skill at both school and undergraduate level. The calculation is straightforward — measure the mass, divide by molar mass to get moles, then divide by volume in litres — but errors in unit conversion (grams vs kilograms, millilitres vs litres) are common, particularly when making small volumes or dilute solutions.

The Concentration Calculator also outputs g/L (mass per litre), which is the unit used in regulatory and analytical contexts: BIS IS 10500 drinking water standards specify TDS limits in mg/L; CPCB effluent discharge norms list maximum concentrations in mg/L; food labelling regulations in India (FSSAI) express additive limits in g/kg or g/L. Being able to see both molarity and g/L at once makes it easier to check whether a prepared solution meets applicable standards.

For the next step — finding how much of this stock solution to use when making a more dilute working solution — see the Solution Dilution Calculator.

How to use this Concentration calculator

  1. Weigh your solute and note the mass — enter the mass in the Mass of Solute field in grams. For example, 5.85 g of NaCl.
  2. Enter Molar Mass of Solute — type the molar mass in g/mol into the Molar Mass of Solute field. For NaCl: Na (22.990) + Cl (35.453) = 58.443 g/mol. Use the Molecular Weight Calculator if you need to calculate this.
  3. Enter Volume of Solution — type the final volume of the solution into the Volume of Solution field in litres. For 100 mL, enter 0.1; for 250 mL, enter 0.25.
  4. Read Molarity (mol/L) — the highlighted output shows the concentration. For 5.85 g NaCl in 0.1 L, the result is 1.001 M.
  5. Read Moles of Solute — verify that moles = mass ÷ molar mass as a consistency check.
  6. Read Mass per Litre (g/L) — use this for regulatory or gravimetric comparisons. For 1 M NaCl: 58.44 g/L. To dilute this stock, use the Solution Dilution Calculator.

Formula & Methodology

Molarity formula:

> C = n / V = (m / M_r) / V

Where:
- C = molarity (mol/L)
- n = moles of solute (mol) = m ÷ M_r
- m = mass of solute (g)
- M_r = molar mass (g/mol)
- V = volume of solution (L)

Mass per litre:

> g/L = m (g) ÷ V (L)

Worked example 1 — NaCl (normal saline context):

Prepare 500 mL of normal saline (0.154 M NaCl, molar mass 58.44 g/mol):
- Moles needed = 0.154 × 0.5 = 0.077 mol
- Mass needed = 0.077 × 58.44 = 4.50 g NaCl
- Dissolve in water and make up to 500 mL exactly

Worked example 2 — Glucose infusion (NEET clinical context):

5% glucose (dextrose) IV solution contains 5 g glucose per 100 mL = 50 g/L. Molar mass of glucose (C₆H₁₂O₆) = 180.16 g/mol:
- Molarity = 50 ÷ 180.16 = 0.278 M glucose
- This is the glucose concentration in a standard 5% dextrose IV bag used in Indian hospitals

Worked example 3 — Laboratory acid dilution:

Concentrated HCl (37%, density 1.19 g/mL, molar mass 36.46 g/mol). Per litre: mass = 1190 g × 0.37 = 440.3 g HCl; molarity = 440.3 ÷ 36.46 = 12.07 M. Knowing this stock concentration, use the Dilution Factor Calculator to plan dilutions to working concentrations like 0.1 M or 1 M HCl.

Frequently Asked Questions

The concentration of a solution is the amount of solute dissolved in a given volume or mass of solvent or solution. The most common expression in chemistry is molarity (mol/L or M): the number of moles of solute per litre of solution. Other expressions include mass per volume (g/L), percent by mass (w/w %), and percent by volume (v/v %). The Concentration Calculator uses molarity as its primary output alongside g/L.
Molarity (C) = moles of solute (n) ÷ volume of solution (V in litres). Moles are calculated first: n = mass (g) ÷ molar mass (g/mol). Combining these: C = mass ÷ (molar mass × volume). For example, dissolving 5.85 g of NaCl (molar mass 58.44 g/mol) in 100 mL (0.1 L) gives n = 5.85/58.44 = 0.1001 mol, and C = 0.1001/0.1 = 1.001 M.
Molarity (M) is moles of solute per litre of solution — the volume includes both solvent and solute. Molality (m) is moles of solute per kilogram of solvent — it uses solvent mass, not solution volume. Molality is temperature-independent (mass doesn't change with temperature), while molarity changes slightly with temperature because solution volume expands or contracts. The Concentration Calculator uses molarity; for colligative property calculations, molality is needed.
Concentration is a general term for how much solute is dissolved per unit of solution — it can be expressed in many units (g/L, mg/mL, ppm, mol/L, etc.). Molarity is one specific type of concentration: moles per litre. When chemists say 'concentration' in the context of solution preparation and stoichiometry, they usually mean molarity. The Concentration Calculator outputs both molarity (mol/L) and mass concentration (g/L) so both forms are available.
To prepare 1 litre of a 1 M solution, weigh out a mass equal to the molar mass of the solute in grams (e.g., 58.44 g of NaCl for 1 M NaCl). Dissolve it in less than 1 litre of solvent, then make up the volume to exactly 1 litre using a volumetric flask. For smaller volumes: to prepare 500 mL of 1 M NaCl, use 58.44/2 = 29.22 g. The Concentration Calculator works in reverse for this — enter the target moles and volume to find the mass needed.
Mass per litre (g/L) is the mass of solute dissolved in one litre of solution, without reference to the solute's molar mass. It is used when the molar mass is unknown (e.g., for polymers or biological extracts), when regulatory standards specify concentrations in g/L or mg/L, or when a simple mass balance is needed. BIS IS 10500 drinking water standards specify TDS in mg/L (equivalent to g/m³). For stoichiometric calculations, molarity (mol/L) is more useful; for gravimetric analysis, g/L is preferred.
Moles of solute is the amount of dissolved substance expressed in moles (mol). It is the intermediate calculation between mass and molarity: moles = mass ÷ molar mass. Knowing moles is essential for stoichiometric reactions — for example, how many moles of HCl are needed to react with a given number of moles of NaOH in a neutralisation. The Concentration Calculator outputs moles of solute explicitly so it can be used directly in reaction calculations.
Enter the mass of solute in grams, the molar mass of the solute in g/mol, and the volume of the final solution in litres. The calculator outputs molarity (mol/L), moles of solute, and mass per litre (g/L). For common solutes: NaCl molar mass = 58.44 g/mol, NaOH = 40.00 g/mol, glucose (C₆H₁₂O₆) = 180.16 g/mol. Use the Molecular Weight Calculator to find molar mass for multi-element compounds.
Normal saline (0.9% NaCl, also called NS) used in Indian hospitals for IV infusion contains 9 g of NaCl per litre (g/L) = 0.9% w/v. In molarity terms: 9 g/L ÷ 58.44 g/mol = 0.154 mol/L = 0.154 M. Half-normal saline (0.45% NaCl) has 4.5 g/L = 0.077 M NaCl. These concentrations match physiological osmolarity and are prescribed per drug formulary standards (e.g., National List of Essential Medicines).
For strong acids (HCl, H₂SO₄, HNO₃), pH gives [H⁺] directly, and for a monoprotic acid, [H⁺] = molarity of the acid. For example, pH 2 → [H⁺] = 0.01 M → molarity of HCl = 0.01 M. However, the Concentration Calculator requires mass and molar mass as inputs — use the pH Calculator for the reverse approach of finding concentration from pH for strong acids.
Solution concentration and molarity are covered in NCERT Class 12 Chemistry Chapter 2 (Solutions). Students learn to calculate molarity, molality, and mass percent from composition data. JEE Main and Advanced regularly include problems involving molarity calculations, mole fractions, and conversion between concentration units. NEET tests concentration calculations in the context of infusions, reagent preparation, and solution stoichiometry.
Common concentrated laboratory reagents available in India: concentrated H₂SO₄ (98%, density 1.84 g/mL) ≈ 18.4 M; concentrated HCl (37%, density 1.19 g/mL) ≈ 12 M; concentrated HNO₃ (69%, density 1.41 g/mL) ≈ 15.7 M; glacial acetic acid (100%, density 1.05 g/mL) ≈ 17.4 M. These must be diluted before use — the Solution Dilution Calculator gives the volumes needed using C₁V₁ = C₂V₂.
Also known as
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