Percent Solids Explained
Percent solids is the mass fraction of solid material in a slurry. Learn the formulas for solids mass flow, liquid mass flow, and slurry mass flow, with a worked example.
Definition
Percent solids is the mass fraction of solid material in a slurry, expressed as a percentage. It is calculated as: percent solids = (solids mass / slurry mass) × 100. The slurry mass is the sum of solids mass and liquid mass. Percent solids is a mass-based measure — it does not directly tell you the volume fraction of solids.
Why it matters
Percent solids is a fundamental parameter in mineral processing, water treatment, and any industry handling slurries. It determines how much useful solid material a stream carries, affects pump sizing, pipe sizing, thickener design, and dewatering equipment selection. Process engineers use percent solids to split total slurry flow into its solid and liquid components for mass balance calculations.
Formula
Units involved
- •%S — percent solids by mass (0 to 100)
- •Solids mass or mass flow in kg, t/h, lb/h, etc.
- •Slurry mass or mass flow in the same units
- •Liquid mass or mass flow in the same units
Concept diagram
Worked example
A slurry stream flows at 100 t/h with 40% solids by mass. What are the solids and liquid mass flow rates?
- 01Slurry mass flow = 100 t/h
- 02Percent solids = 40%
- 03Solids flow = 100 × 40 / 100 = 40 t/h
- 04Liquid flow = 100 − 40 = 60 t/h
Solids flow = 40 t/h; Liquid flow = 60 t/h
Common mistakes
- •Confusing percent solids by mass with percent solids by volume — they are different because solids and liquid have different densities. This guide and the calculator use mass-based percent solids.
- •Using slurry volume instead of slurry mass in the formula — percent solids is a mass ratio, not a volume ratio.
- •Forgetting that slurry mass = solids + liquid — some people mistakenly use solvent mass in the denominator instead of total slurry mass.
- •Assuming percent solids tells you slurry density — you need to know the solids density and liquid density to calculate slurry density from percent solids.
- •Applying the formula to dissolved solutes — percent solids refers to undissolved solid particles in a slurry, not dissolved material in a solution.
When to use the calculator
Use the Slurry Solids calculator when you know any two of the three values (slurry flow, solids flow, percent solids) and need the third. The calculator also computes the liquid flow and handles unit conversions between mass flow units.