How do you calculate screw feeder throughput?

Divide completed output by runtime for the raw rate, then multiply by efficiency. Here 1,200 units over 8 hours is a 150-unit raw rate, and at 90% efficiency the effective rate is 135.

What is the difference between raw and effective feed rate?

Raw rate (150 here) is total output divided by clock time and assumes steady flow. Effective rate (135) accounts for refill pauses and surging, so it is what you should size the downstream process to.

What is a good efficiency for a loss-in-weight feeder?

Well-tuned loss-in-weight feeders on free-flowing material hold 92-98%; the 90% default fits a moderately cohesive powder with regular refills. Below 85%, bridging or refill control usually needs attention.

Why is my actual feed rate lower than the spec?

Nameplate rates assume continuous flow. Real runs lose time to gravimetric refills, screw surging, and material that bridges in the hopper, which is exactly the 10% gap between 150 and 135 in this example.

How do I improve screw feeder efficiency?

Steady the hopper level, add agitation or vibration for cohesive material, and tune the refill cycle so it does not interrupt dosing. Each of these pushes effective rate closer to the raw 150-unit ceiling.

Does runtime include refill and downtime?

Runtime is total clock time, so refills inside the run are captured by the efficiency factor rather than removed from runtime. That is why effective rate, not raw rate, is the number to plan around.

Weighing, Dosing & Loss-in-Weight Feeding calculator

Screw Feeder Rpm Calculator

Effective screw feeder output is the real, derated dosing rate a loss-in-weight feeder sustains once you account for refill pauses, surging, and material bridging that the nameplate rate ignores. Process engineers and packaging-line technicians running powders, pellets, or granules use it to confirm a feeder can actually keep a downstream blender or filler supplied. The raw rate from output divided by runtime looks clean, but a feeder rated at 150 units that only delivers 135 will quietly starve the line during refills. This calculator turns a measured run into the honest rate you can design around.

What this calculator does

Calculate screw feeder rpm for weighing, dosing & loss-in-weight feeding planning, quoting, troubleshooting, capacity review, or process improvement.
Use it when screw feeder rpm in weighing, dosing and loss-in-weight feeding is being committed and you need a throughput number you can defend.
It divides completed output by runtime for a raw feed rate, then applies an efficiency factor to give the effective sustained rate.

Formula used

Raw screw feeder rpm = completed output ÷ runtime
Effective screw feeder rpm = raw throughput × efficiency

Inputs explained

Screw Feeder Rpm completed output: undefined
Screw Feeder Rpm runtime: undefined
Screw Feeder Rpm efficiency: undefined

How to use the result

Use it after a timed dosing trial to set a realistic feed rate before committing a feeder to a recipe or line speed.
It models efficiency as a single flat factor; bridging, ratholing, or refill surges that vary with material and hopper level are not separated out.

Common questions

How do you calculate screw feeder throughput? Divide completed output by runtime for the raw rate, then multiply by efficiency. Here 1,200 units over 8 hours is a 150-unit raw rate, and at 90% efficiency the effective rate is 135.
What is the difference between raw and effective feed rate? Raw rate (150 here) is total output divided by clock time and assumes steady flow. Effective rate (135) accounts for refill pauses and surging, so it is what you should size the downstream process to.
What is a good efficiency for a loss-in-weight feeder? Well-tuned loss-in-weight feeders on free-flowing material hold 92-98%; the 90% default fits a moderately cohesive powder with regular refills. Below 85%, bridging or refill control usually needs attention.
Why is my actual feed rate lower than the spec? Nameplate rates assume continuous flow. Real runs lose time to gravimetric refills, screw surging, and material that bridges in the hopper, which is exactly the 10% gap between 150 and 135 in this example.
How do I improve screw feeder efficiency? Steady the hopper level, add agitation or vibration for cohesive material, and tune the refill cycle so it does not interrupt dosing. Each of these pushes effective rate closer to the raw 150-unit ceiling.

Last reviewed 2026-05-12.