How do you calculate hopper refill interval?

Divide the usable hopper charge by the feeder throughput to get base run time, then multiply by the allowance factor. A 120 kg charge at 12 kg/hr gives 10 hours base, and a 10% allowance extends it to about 11 hours.

Why add a safety allowance to the refill interval?

The allowance keeps the hopper above its low-level trigger and buffers rate variation, so refills are prompted before the feeder starves. It builds slack into the schedule rather than running the hopper to empty.

What is usable hopper charge versus total capacity?

Usable charge is the mass between the fill level and the low-level trigger, not the geometric capacity. Material below the trigger is reserved to keep weighing stable, so always plan against the usable figure.

How does refill timing affect dosing accuracy?

During a refill, the sudden weight gain disturbs a loss-in-weight feeder's gravimetric signal, forcing it into volumetric control briefly. Scheduling refills predictably lets you cluster that disturbance away from critical doses.

What if my feeder throughput changes during the run?

The interval assumes a constant rate, so a mid-run rate increase shortens the real interval and a decrease lengthens it. Recompute whenever the recipe or setpoint changes materially.

Should the allowance make the interval longer or shorter?

In this model the allowance factor extends the base time to represent planning slack, so the adjusted interval of 11 hours is longer than the 10-hour base. If you instead want an earlier refill trigger, apply the allowance as a reduction.

Weighing, Dosing & Loss-in-Weight Feeding calculator

Hopper Refill Interval Calculator

Hopper Refill Interval estimates how long a feeder hopper can run before it needs topping up, based on the usable charge and the feeder's throughput, with a safety allowance to keep the hopper above its low-level trigger. Production planners and feeder operators use it to schedule refills so a loss-in-weight feeder never runs dry or drops into a level that disturbs weighing. Because refills are the single biggest source of feed-rate disturbance, timing them predictably protects both throughput and dosing accuracy. It turns hopper capacity and feed rate into an actionable refill cadence.

What this calculator does

Hopper Refill Interval estimates how long a feeder hopper can run before it needs topping up, based on the usable charge and the feeder's throughput, with a safety allowance to keep the hopper above its low-level trigger.
Use it when hopper refill interval in weighing, dosing and loss-in-weight feeding is changing rate or allowance and you want to see the impact.
It computes the base run time as usable charge divided by throughput, then extends it by a safety allowance factor to give an adjusted refill interval.

Formula used

Time to empty = usable hopper charge ÷ feeder throughput
Planned refill interval = time to empty ÷ (1 + refill safety allowance)

Inputs explained

Usable hopper charge:
Feeder throughput:
Refill safety allowance:

How to use the result

Use it when planning refill logistics or staffing a line so refills land on schedule rather than at random low-level alarms.
It assumes a steady throughput; if the feeder rate ramps or the recipe changes mid-run, the real interval will differ from the constant-rate estimate.

Common questions

How do you calculate hopper refill interval? Divide the usable hopper charge by the feeder throughput to get base run time, then multiply by the allowance factor. A 120 kg charge at 12 kg/hr gives 10 hours base, and a 10% allowance extends it to about 11 hours.
Why add a safety allowance to the refill interval? The allowance keeps the hopper above its low-level trigger and buffers rate variation, so refills are prompted before the feeder starves. It builds slack into the schedule rather than running the hopper to empty.
What is usable hopper charge versus total capacity? Usable charge is the mass between the fill level and the low-level trigger, not the geometric capacity. Material below the trigger is reserved to keep weighing stable, so always plan against the usable figure.
How does refill timing affect dosing accuracy? During a refill, the sudden weight gain disturbs a loss-in-weight feeder's gravimetric signal, forcing it into volumetric control briefly. Scheduling refills predictably lets you cluster that disturbance away from critical doses.
What if my feeder throughput changes during the run? The interval assumes a constant rate, so a mid-run rate increase shortens the real interval and a decrease lengthens it. Recompute whenever the recipe or setpoint changes materially.
Should the allowance make the interval longer or shorter? In this model the allowance factor extends the base time to represent planning slack, so the adjusted interval of 11 hours is longer than the 10-hour base. If you instead want an earlier refill trigger, apply the allowance as a reduction.

Last reviewed 2026-08-13.