Core Formulas

How to Calculate Conveyor Capacity, Crusher Throughput, and Screen Efficiency

The five formulas that govern material handling in mining and aggregates, worked through with real tonnage, densities, and mesh figures so you can compute them yourself.

Belt conveyor capacity starts from Q = 3600 x A x v x rho, where A is the loaded cross-section in square meters, v is belt speed in meters per second, and rho is bulk density in tonnes per cubic meter. A 1200 mm belt at a 20 degree surcharge carries roughly A = 0.045 m2. Run it at v = 2.5 m/s on limestone at rho = 1.6 t/m3 and you get Q = 3600 x 0.045 x 2.5 x 1.6 = 648 t/h. The Conveyor Capacity tool bundles surcharge and trough angle into the effective area so you enter belt width and speed directly.

Belt Load, the mass sitting on the belt per unit length, follows m = Q / (3.6 x v) in kg/m. Using the 648 t/h and 2.5 m/s above, m = 648 / (3.6 x 2.5) = 72 kg/m. That figure feeds idler selection and drive power: the belt tension to lift and move that load over length L and lift H drives motor sizing. Get Belt Load wrong and you either overspend on idlers rated for 150 kg/m or overload frames rated for 40 kg/m. Always separate the running mass from the material tonnage rate.

Crusher throughput scales with the closed side setting and the material work index. A jaw crusher rated at a 125 mm CSS on granite at rho = 1.5 t/m3 might pass 350 t/h; tighten the CSS to 100 mm and throughput drops near 260 t/h because the choke volume per stroke shrinks. The Crusher Throughput calculator takes feed size, CSS, and eccentric speed, then applies a reduction ratio, typically 4:1 to 7:1 for jaws and 3:1 to 5:1 for cones, so you can size the downstream conveyor to the actual crusher output, not the nameplate.

Screen efficiency measures how much undersize the deck actually passes: E = (undersize in oversize removed) relative to undersize in feed, or more usefully E = mass of correct product passing / mass of undersize in feed, times 100. If the feed carries 40 t/h of minus 10 mm material and the deck only sends 34 t/h through the apertures, E = 34 / 40 = 85 percent. Typical single-deck screens run 85 to 95 percent. The Screen Efficiency tool separates feed rate, near-size fraction, and aperture so you can isolate whether the loss is blinding, overloading, or too steep a stroke angle.

Aggregate yield converts a shot or a feed stream into saleable product by fraction. If a pit processes 500 t/h of run-of-mine and the target 20 mm product represents 28 percent of the gradation with a 4 percent process loss, sellable yield = 500 x 0.28 x 0.96 = 134.4 t/h. Aggregate Yield lets you enter the full gradation split so each product size gets its own tonnage. This is the number that ties crusher and screen output back to what leaves the scale house, and it exposes fines you cannot sell.

Silo capacity is straight geometry plus packing. A cylinder of diameter D and cylindrical height h holds V = pi x (D/2)^2 x h, and a conical bottom adds V = (1/3) x pi x r^2 x hc. A 6 m diameter silo with 12 m of straight side holds pi x 9 x 12 = 339 m3; add a 3 m cone at pi x 9 x 3 / 3 = 28 m3 for 367 m3. Multiply by rho to get mass: at 1.4 t/m3 for cement, that is 514 tonnes. Silo Capacity handles the cone and the angle of repose fill line so you do not overstate usable volume.

Bulk density conversion is the input error that quietly ruins every calculation above. Loose poured, tapped, and aerated densities of the same powder can differ by 30 to 50 percent. Sand might read 1.45 t/m3 loose but 1.68 t/m3 compacted, and a truck spec quoted in loose cubic yards will not match a silo filled by gravity settling. Bulk Density Conversion moves you between kg/m3, t/m3, lb/ft3, and lb/yd3, and lets you apply a compaction factor so the density you feed into conveyor and silo math matches the real state of the material.

Screw Conveyor Throughput and Powder Flow Rate close out the set for enclosed handling. Screw capacity is Q = 60 x (pi/4) x (Ds^2 - Dp^2) x P x N x C x rho, where Ds is trough diameter, Dp is shaft diameter, P is pitch, N is rpm, and C is the loading factor, usually 0.3 to 0.45 for free-flowing solids. A 0.3 m screw at 0.3 m pitch, 60 rpm, C = 0.4, on grain at 0.75 t/m3 yields near 22 t/h. Powder Flow Rate ties the mass flow through an orifice back to hopper design so feed to that screw stays consistent.

Published 2026-07-01.