20
g/L
20,000
mg/L
2
% w/v
20
mg/mL
2
g/100 mL
20
g/L
20,000
mg/L
2
% w/v
20
mg/mL
2
g/100 mL
The mass concentration (also called mass-volume concentration) is one of the simplest and most practical ways to express how much solute is dissolved in a solution. It is defined as the mass of solute divided by the volume of solution: C = m / V, typically expressed in grams per liter (g/L) or milligrams per liter (mg/L). This unit is especially common in clinical chemistry, environmental science, food science, and industrial applications.
Unlike molarity, mass concentration does not require knowledge of the solute's molar mass, making it universally applicable. When a pharmaceutical label states "500 mg/5 mL" or an environmental report quotes "10 mg/L of lead," they are using mass concentration. This calculator takes the mass of solute in grams and the solution volume in milliliters, then computes the concentration in g/L, mg/L, and approximate weight-per-volume percent (% w/v).
The weight-per-volume percent (% w/v) is defined as grams of solute per 100 mL of solution. A 1% w/v solution contains 1 g of solute per 100 mL, or equivalently 10 g/L. This unit is extremely common in medical and pharmaceutical contexts — for example, normal saline is 0.9% w/v NaCl.
The mass concentration formula is straightforward:
C = msolute / Vsolution
Where:
This calculator accepts volume in milliliters for convenience and converts internally to liters. The outputs include:
To convert mass concentration to molarity, divide by the molar mass: Molarity = C (g/L) / Mw (g/mol). For instance, 10 g/L of NaCl (Mw = 58.44) corresponds to 0.171 M.
For dilute aqueous solutions, mg/L is numerically equivalent to parts per million (ppm) because the density of water is approximately 1 g/mL. However, for non-aqueous solvents or concentrated solutions, this approximation does not hold, and density corrections are needed.
In practice, mass concentration is determined by weighing a known mass of solute on an analytical balance, transferring it to a volumetric flask, dissolving completely, and adding solvent to the calibration mark. The precision of the result depends on the accuracy of the balance and the flask.
A concentration of 10 g/L means 10 grams of solute are present in every liter of solution. In mg/L terms, this is 10,000 mg/L. For reference, drinking water standards typically limit contaminants to the mg/L or even μg/L range — for example, the WHO guideline for arsenic in drinking water is 0.01 mg/L (10 ppb).
The % w/v output shows approximate weight-per-volume percentage, useful for quick comparisons with pharmaceutical labels. Normal saline (0.9% NaCl) would show as 9 g/L or 9000 mg/L.
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Dissolving 9 g of NaCl in enough water to make 1000 mL yields 0.9% w/v saline, the standard isotonic solution used in medical practice.
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Finding 25 mg of dissolved solids in a 500 mL water sample indicates a concentration of 50 mg/L. This is well within typical drinking water TDS ranges (< 500 mg/L per WHO guidelines).
They differ only by a factor of 1000. One g/L equals 1000 mg/L. The g/L unit is used for higher concentrations (e.g., blood glucose around 1 g/L), while mg/L is used for lower concentrations (e.g., water pollutants, trace elements).
For dilute aqueous solutions at room temperature, yes — 1 mg/L ≈ 1 ppm because the density of water is approximately 1 kg/L. However, for non-aqueous solutions, concentrated solutions, or gases, this equivalence does not hold and you must use: ppm = (mg/L) / density (kg/L).
Percent weight per volume (% w/v) is the mass of solute in grams per 100 mL of solution. A 5% w/v glucose solution contains 5 g of glucose in every 100 mL. This notation is standard in pharmacology, medicine, and food labeling.
Divide the mass concentration in g/L by the molar mass in g/mol: Molarity = C (g/L) / Mw (g/mol). For example, a 40 g/L NaOH solution has a molarity of 40 / 40.00 = 1.0 M.
Yes, but slightly. Since volume changes with temperature (thermal expansion), the same mass of solute in an expanded volume gives a lower concentration. For most practical purposes below 50°C, the effect is small. For precise work, prepare solutions at a standard temperature and use temperature-corrected volumetric glassware.
Weight per volume (w/v) uses solution volume as the denominator (g per 100 mL), while weight per weight (w/w) uses solution mass (g per 100 g). The w/w percentage is independent of temperature since it is based entirely on mass. They are related by solution density: % w/v = % w/w × density (g/mL).
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