Stock Placement Calculator

1. Enter your SKU, daily sales, lead time, and service level.
2. Add demand variability (daily standard deviation) for realistic safety stock.
3. Set pick assumptions: units per order, unit volume, and days of cover.
4. Adjust zone distances and handling seconds to match your warehouse layout.
5. Click Calculate and review the recommended zone and time tradeoffs.
6. Export results to CSV or PDF for sharing and documentation.

Demand velocity segmentation

Fast movers often create most picks, so velocity deserves first attention. Track units per day, orders per day, and pick frequency. For example, 40 units/day at 2 units/order yields 20 picks/day. Items above 30 picks/day usually merit the shortest travel paths. Add a second tier using value: unit price times daily units approximates daily value.

Pick-face capacity and space

Pick slots should cover planned days of supply plus safety stock. If cover is 7 days, cycle stock equals 280 units at 40 units/day. Add safety stock from variability to avoid stockouts. Convert units to liters using unit cube; 800 cm3 each becomes 0.8 L. A 350 unit slot needs about 280 L. Compare that to zone capacity.

Service level and reorder point

Reorder point aligns replenishment with lead time demand. Demand during lead time equals average daily sales times lead time days. Variability scales with the square root of lead time, so longer lead times magnify uncertainty. At 95% service, z is about 1.65, and safety stock equals z times lead time sigma. If daily standard deviation is 12 and lead time is 10, sigma is roughly 38, producing about 63 units of safety stock. That buffer can reduce late shipments and cancellations.

Travel time, handling, and replenishment

Placement decisions can be compared as minutes per day. Travel seconds equal distance divided by walking speed, then add scan and grab seconds. Multiply by picks per day to estimate daily picking minutes. Add replenishment minutes using estimated replenishment events per day times restock minutes per event. Case pack matters: rounding replenishment to full cases lowers event count but increases on hand volume. Use the chart to spot when prime labor savings are offset by frequent restocks.

Recommendation and governance

Use the recommended zone as a policy, not a one time choice. Review inputs monthly, especially average sales, lead time, and demand variability. Flag items whose pick-face volume exceeds prime capacity, then move them to standard or bulk. Audit pick errors, damage rate, and congestion in the fastest aisles. Track savings versus baseline and update slotting rules after promotions or supplier changes.

What does the recommended zone mean?

It is the feasible zone with the lowest estimated daily minutes, combining picking travel, handling, and replenishment time for the current demand profile.

How is safety stock calculated here?

Safety stock equals z times the lead time standard deviation. The lead time deviation is the daily deviation multiplied by the square root of lead time days.

Why do I need units per order?

Units per order converts unit sales into pick frequency. Higher picks per day amplify travel time differences between zones, which can change the best placement.

How should I estimate unit volume?

Use product dimensions to approximate cube volume in cubic centimeters, including packaging. When uncertain, measure a shipped unit and use that value for consistent slot sizing.

What if prime capacity is too small?

If required pick-face volume exceeds prime capacity, the zone becomes infeasible. Increase capacity, reduce days of cover, or place the item in standard or bulk storage.

Can I use this for seasonal spikes?

Yes. Run scenarios with higher average sales and variability, then compare zone totals. Recalculate after promotions and adjust days of cover to control replenishment workload.