Concentration calculator
Calculate common solution concentrations from mass, volume, molarity, molar mass, and density using five standard chemistry relationships.
Inputs
Results
Calculation breakdown
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How to use this concentration calculator
What this calculator does
This calculator evaluates five common concentration relationships used in solution preparation. It can determine mass/volume percent, mass percent, convert molarity to mass percent, convert mass percent to molarity, or express dissolved solute as grams per 100 grams of water. It performs arithmetic from the values you enter; it does not verify chemical compatibility, activity coefficients, temperature effects, purity, measurement uncertainty, or whether a substance actually dissolves at the stated concentration.
When to use it
Use it when preparing a laboratory solution from a known solute mass and final volume, checking a formulation stated as weight percent, converting a molar recipe into an approximate mass-percent composition when density is known, or comparing a food, brine, cleaning, or process solution on a grams-per-100-grams-water basis. It is also useful for documenting calculations in a reproducible Excel workbook.
How to calculate
- Choose a relationship from I want to calculate. The field labels and units update to match that method.
- Enter each required value using a period as the decimal separator. Plain decimals such as 5, 58.44, and 1.05 are accepted; scientific notation, percent signs, commas, and unit text are rejected.
- Read the live primary result, then review Ratio, Formula, the interpretation, and the Calculation breakdown table.
- Select Download Excel to create a current-state OOXML workbook containing Summary, Inputs, and Notes sheets. Select Reset to restore the initial mass/volume example of 5 g in 100 mL.
Input guide
I want to calculate is required and selects the formula. Input A, Input B, and when shown Input C are required nonnegative or positive decimal measurements. In mass/volume mode, enter Mass of solute in grams and Volume of solution in milliliters; for example, 5 g and 100 mL. In mass-percent mode, enter solute mass and total solution mass in the same mass unit, and keep solute mass no greater than solution mass. For molarity conversions, use molarity in mol/L, molar mass in g/mol, and density in g/mL. A higher solute mass, molarity, molar mass, or density can raise the computed concentration depending on the selected equation. A common mistake is using solvent volume instead of final solution volume, or mixing density units such as kg/L and g/mL without conversion.
Output guide
The primary result is the requested concentration or composition value. Ratio shows a closely related unscaled ratio or mass loading. Formula identifies the active relationship. The interpretation states what the number means physically and whether it is a direct identity or a density-based conversion. The Calculation breakdown table lists each entered quantity and the derived result with units. Zero is valid only where zero solute or zero concentration is physically meaningful; denominators, density, molar mass, and final solution mass must be greater than zero. Very high mass percentages approaching 100% make the grams-per-100-g-water result grow sharply because little water remains.
Worked example
For the default mass/volume calculation, 5 g of solute is present in 100 mL of final solution. The calculator divides 5 g by 100 mL to obtain 0.05 g/mL, then multiplies by 100 mL: w/v% = (5 ÷ 100) × 100 = 5.00% w/v. The displayed interpretation, breakdown table, and exported workbook all report 5.00 g per 100 mL.
Learn more
The IUPAC Gold Book definition of concentration explains concentration as a quantity describing composition. For unit conventions and careful expression of measured quantities, consult the NIST Guide for the Use of the International System of Units. For molarity terminology, see the IUPAC definition of amount concentration.
Formula notes
Mass/volume percent is grams of solute per 100 mL of final solution. Mass percent is solute mass divided by total solution mass times 100. Converting molarity to mass percent uses molarity × molar mass divided by solution density, with density converted from g/mL to g/L. The reverse conversion divides the solute mass per liter by molar mass.
Practical limits
Density depends on temperature and composition, so density-based conversions are estimates unless density is measured under matching conditions. Significant figures should reflect the least precise input. For regulated, medical, or safety-critical preparations, follow a validated procedure and calibrated equipment rather than relying on a general-purpose calculator alone.