Screw Conveyor Capacity and Power Calculator

Capacity in tonnes per hour and the drive power for a screw conveyor, from its flight geometry, speed and the material.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

A screw conveyor moves material along a trough with a rotating helical flight. The volume per hour is the flight area minus the shaft area, times the pitch, the speed and the fill (loading) factor. The mass is the volume times the bulk density.

The power is the sum of the power to push the material along the trough against friction, using a material friction factor, and the power to lift it if the screw is inclined, divided by the drive efficiency. Material factors and fill depend on how free-flowing, abrasive or sticky the material is, so use the supplier or conveyor handbook values.

Formulas used

  • Q_V = \frac{\pi}{4}(D^2 - d^2)\,S\,n\,\psi
  • Q_m = Q_V \rho_b
  • P = \frac{Q_m g\,(\lambda L + H)}{\eta}

Worked example

With the default numbers in the calculator above:

  1. Annular flight area: 29452 mm²
  2. Capacity: 3.39 t/h
  3. Power: 0.136 kW
  4. Drive torque: 32.5 N·m

Change the numbers in the calculator to see the full working, every step, for your own case.

Common questions

What fill factor is typical?

About 0.3 to 0.45 for free-flowing material and 0.15 to 0.3 for abrasive or sticky material.

What is the material friction factor?

A number for how hard the material drags on the trough and flights. Handbooks list a value for each material, roughly 1.2 to 4.

Does inclination reduce capacity?

Yes. Capacity falls as the angle rises, and the fill factor should be lower for inclined screws.

Related calculators

Further reading: CEMA screw conveyor methods and conveyor handbooks (cited as the source of the method only).

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