What is the difference between molarity (M) and molality (m)?

Molarity is mol/L of solution and depends on volume; molality is mol/kg of solvent and depends on mass.

What is normality and what does n_eq mean?

Normality is equivalents per liter (eq/L). n_eq indicates how many equivalents each mole of solute contributes.

How is % m/v defined?

It is defined as grams of solute per 100 mL of solution (% m/v = g/100 mL).

What is the difference between ppm w/w and ppm ≈ mg/L?

ppm w/w is mg of solute per kg of solution. ppm ≈ mg/L is an approximation valid only in water (ρ≈1 g/mL).

Why is density needed for some conversions?

Density connects mass and volume; without it you cannot convert from % w/w to volume-based units (M, g/L, etc.).

How do you calculate a simple dilution?

Use C1·V1=C2·V2; solve for the unknown and compute diluent volume as V2−V1.

How do you mix two solutions with different units?

Convert each solution to total solute mass and add them; then compute the final concentration.

What limitations and assumptions does the calculator use?

It assumes ideal mixing, additive volume (if enabled), and requires MW, density, or n_eq for specific conversions.

Solutions and concentrations calculator

Convert molarity, molality, normality, percentages, ppm/ppb; calculate dilutions, mixes and serial dilutions with steps, tables and CSV export.

Solutions and concentrations calculator

Convert between molarity, molality, normality, percentages and ppm/ppb. Calculate dilutions, mixes and serial dilutions with steps, tables and CSV export.

By default, ppm is ppm w/w (mg/kg). Enable the water approximation if you want ppm ≈ mg/L.

1) Input data

Base solution

Concentration

Unit

Solution volume (optional)

Volume unit

Molar mass MW (g/mol)

Density ρ (g/mL)

n_eq factor (eq/mol)

ppm ≈ mg/L (water)

Enable approximation

Results to show

2) Results

Equivalence table

CSV

Decimals

Unit	Value	Action

Copyable summary

3) Totals (if volume)

Solute totals

1) Dilution data

C₁ · V₁ = C₂ · V₂

C1 (stock)

Unit

V1 (pipette)

Target V2

Target C2

Fill in V1 or C2 depending on the unknown.

Volume unit

I want to calculate

Difficult pipetting threshold (µL)

Prepare N tubes

2) Result and protocol

Result

CSV

Decimals

—

Tube	V1	Diluent	V2

1) Solutions to mix

Solution list

Additive volume

Assume V_tot = ΣV (approx.)

n_eq for final normality

ppm ≈ mg/L (water)

Enable approximation

Final units

2) Result and table

Overall result

CSV

Decimals

—

Solution	m_s (g)	n (mol)	V (L)	Contribution

1) Setup

Serial dilution

Initial C0

Unit

Number of steps

Method

Factor X

Base Vt (optional)

Volume unit

Log scale

Use log10

2) Table and chart

Results per step

CSV

Decimals

Step	Concentration	Vt	Diluent	Cumulative factor

Chart

Improve this calculator

Found an error or missing a feature?

Send us the example so we can review this calculator and turn real cases into improvements or automated tests.

Base solution

Equivalence table

Solute totals

C1 · V1 = C2 · V2

Result

Solution list

Overall result

Serial dilution

Results per step

Step by step

Found an error or missing a feature?

You may also like

Fluid mixing: final temperature, concentration & density

C₁ · V₁ = C₂ · V₂