Solubility Product Calculator
Solubility product from molar solubility and back — for any salt stoichiometry, with the common-ion effect.
For a salt AxBy dissolving to xA + yB, the solubility product is Ksp = (xs)ˣ(ys)ʸ where s is the molar solubility.
How the solubility product calculator works
For a salt AxBy dissolving to xA + yB, the solubility product is Ksp = (xs)ˣ(ys)ʸ where s is the molar solubility. Rearranged, s = (Ksp / (xˣyʸ))^(1/(x+y)).
The stoichiometry matters more than people expect. Two salts with the same Ksp but different formulas have quite different solubilities, which is why Ksp values cannot be compared directly across salt types.
Formula: Ksp = (xs)^x (ys)^y
Worked examples
| Inputs | Result | Note |
|---|---|---|
| Silver chloride, Ksp 1.8 × 10⁻¹⁰ | 0.00001341640786 | 1.34 × 10⁻⁵ M — 1.9 mg/L |
| Back to Ksp | 1.7956e-10 | 1.8 × 10⁻¹⁰ |
| A 1:2 salt | 0.00035568933045 | a different solubility for the same Ksp |
FAQFrequently asked questions
What is the solubility product?
The equilibrium constant for a sparingly soluble salt dissolving — the product of its ion concentrations, each raised to its coefficient.
Can I compare Ksp values directly?
Only between salts of the same stoichiometry. A 1:1 and a 1:2 salt with identical Ksp have very different solubilities.
What is the common ion effect?
Adding one of the ions from another source pushes the equilibrium back and suppresses solubility. It is how silver is recovered by adding excess chloride.
How soluble is silver chloride?
About 1.9 mg per litre — enough to call it insoluble in everyday terms, but far from zero.
Does temperature change Ksp?
Yes, usually upward for solids dissolving. Published values are for 25 °C unless stated.
Where these figures come from
- IUPAC — Standard atomic weights (2021 conventional values) — the molar-mass table
- NIST — CODATA 2018 fundamental physical constants — Avogadro constant, gas constant, speed of light
- NIST Chemistry WebBook — thermochemical data
- Royal Society of Chemistry — the UK chemistry professional body
Last checked: September 2026. Atomic masses are the IUPAC conventional values; constants are CODATA 2018; equations are the standard textbook forms.