Figures are sourced and dated. Check them before relying on them in client work.
Warehouse Backlog and Queue Calculator
Simulate work backlog through a peak season, daily inflow vs processing capacity → how deep the queue gets, whether you breach your service tolerance, and how long to clear. Pair the capacity figure with your Labor estimate. Calculations run server-side.
Peak = baseline × this
Baseline tail to watch clear-down
From your Labor estimate
Surge staffing / temps / OT
Set your daily inflow, processing capacity, and service tolerance, peak backlog, time to clear, and SLA verdict appear here.
What this calculator does
This calculator simulates a work backlog through a peak season. It compares daily inflow with processing capacity across a ramp-up, a peak plateau, a ramp-down and a recovery period, then reports how deep the queue gets, whether it breaches your service tolerance and how many days it takes to clear.
Inputs that matter
- Demand: baseline units per day, a peak multiplier, and the number of days in the ramp-up, peak, ramp-down and recovery phases.
- Capacity: base capacity per day, and a separate peak capacity per day that applies for the whole surge window (ramp-up, peak and ramp-down).
- Service: a tolerance in days behind. Any day on which the queue is deeper than this counts as a breach.
How it works
Peak volume is the baseline times the multiplier. Daily inflow is a trapezoid: it rises in even steps from the baseline to peak volume over the ramp-up, holds at peak, falls back over the ramp-down, then stays at the baseline for the recovery days.
Each day the model carries the backlog forward: backlog equals the larger of zero and yesterday's backlog plus today's inflow minus today's capacity. Capacity is the peak figure during the surge window and the base figure afterward. Days behind is the backlog divided by base capacity per day.
The results report the peak backlog and the day it occurs, peak days behind, the number of breach days and the first breach day, and the time to clear after the surge ends. If the queue has not cleared by the end of the simulated horizon, the tool projects the clear day using the drain rate, which is base capacity minus the baseline. If base capacity does not exceed the baseline, the backlog never clears.
Frequently asked questions
- What does days behind mean?
- It is the backlog divided by base capacity per day, so it tells you how many normal days of work are waiting in the queue. A backlog equal to one day of base capacity is one day behind.
- What happens if the backlog never clears?
- After the surge, the queue drains at base capacity minus the baseline each day. If base capacity is at or below the baseline, that drain rate is zero or negative, so the tool reports that the backlog never clears. Raising base capacity above the baseline is what lets it drain.
- How is the service tolerance used?
- Any day with days behind above your tolerance counts as a breach. The tool reports whether a breach occurred, how many breach days there were and the first breach day.