Solubility Product (Ksp) Calculator
Enter the compound's molar solubility and the number of cations and anions it releases per formula unit to calculate Ksp.
Last updated: September 5, 2026
Frequently asked questions
What is the solubility product constant (Ksp)?
An equilibrium constant for a sparingly soluble ionic compound, equal to the product of its dissolved ion concentrations (each raised to its stoichiometric coefficient) at saturation - a lower Ksp means the compound is less soluble.
How do I calculate Ksp for CaF₂ (calcium fluoride)?
CaF₂ dissolves as 1 Ca²⁺ and 2 F⁻ per formula unit, so with molar solubility s: [Ca²⁺] = s, [F⁻] = 2s, and Ksp = s × (2s)² = 4s³. Enter cation coefficient 1 and anion coefficient 2 above.
Why is the anion concentration multiplied by its coefficient before being raised to a power?
Each formula unit that dissolves releases y anions, not just 1, so the anion concentration at saturation is y times the molar solubility - that scaled concentration is what gets raised to the power y in the Ksp expression, following the reaction stoichiometry.
Does this work for any compound, or just 1:1 and 1:2 ratios?
It works for any x:y cation-to-anion ratio - enter the actual stoichiometric coefficients from the compound's formula (like 2 and 3 for a compound like Al₂S₃) and the calculator applies the same general formula.
Can Ksp be used to predict whether a precipitate will form?
Yes, indirectly - by comparing the actual ion product (Q) in a solution to Ksp: if Q > Ksp, a precipitate forms because the solution is supersaturated; if Q < Ksp, more solid can still dissolve. This calculator finds Ksp itself, the saturation benchmark for that comparison.
Does a higher Ksp always mean a compound is more soluble?
Only when comparing compounds with the same ion ratio (like two 1:1 salts) - because the Ksp formula raises concentrations to different powers depending on stoichiometry, comparing Ksp values directly across compounds with different x:y ratios can be misleading.
What is Ksp for a simple 1:1 salt like AgCl with molar solubility 1.3×10⁻⁵ mol/L?
About 1.69×10⁻¹⁰ - for a 1:1 salt, [Ag⁺] = [Cl⁻] = s, so Ksp = s² = (1.3×10⁻⁵)² ≈ 1.69×10⁻¹⁰.