How do you calculate a supply-demand gap?

Multiply daily usage by lead time to get cycle stock, add safety stock for the required inventory, then compare that against on-hand stock. With 1,200 units/day over an 85-day lead time, the coverage math yields about 12.83 protected days versus 14.12 unprotected days.

What does protected days of supply mean?

It is the number of days your current on-hand inventory can cover average demand before it runs out. In the worked example that is 12.83 days, so anything beyond that window is exposed to a stockout unless replenishment arrives sooner.

What is the difference between cycle stock and safety stock?

Cycle stock (usage times lead time) covers expected demand during replenishment, while safety stock is the extra buffer that absorbs demand spikes and supplier variability. The calculator sums both to size the required position.

What is a good supply-demand gap?

Ideally the gap is zero or slightly positive, meaning protected days meet or exceed your lead time. A shortfall like 12.83 protected days against an 85-day lead time signals a serious replenishment gap that needs a purchase order or an alternate source.

How does lead time affect the gap?

Longer lead times raise required cycle stock proportionally. Doubling an 85-day lead time doubles the cycle stock you must carry to hold the same protected coverage, which is why lead-time reduction is often cheaper than adding inventory.

Can this replace a full MRP run?

No. It is a fast single-item sanity check. MRP nets demand across BOM levels, open orders and time buckets, whereas this calculator answers a focused question about one part's coverage.

S&OP, Demand Planning & Forecasting calculator

Supply Demand Gap Calculator

The supply-demand gap measures whether the inventory you hold covers the demand that will land before your next replenishment arrives. Demand planners and materials managers use it to translate raw stock counts into days of coverage, exposing the window where consumption outruns supply. On the floor it is the difference between a controlled buffer and an unplanned line stoppage. Framing the gap in days rather than units makes it directly comparable to your quoted lead time.

What this calculator does

Estimate supply demand gap for sandop, demand planning and forecasting using production-ready inputs so teams can plan replenishment and safety stock using actual usage and lead time.
Use it when supply demand gap in s and op, demand planning and forecasting is being sized for a buffer or safety stock review.
It computes required inventory as cycle stock (daily usage times lead time) plus safety stock, then reports how many days of supply are actually protected versus exposed.

Formula used

Supply demand gap cycle stock = supply demand gap daily usage × supply demand gap lead time
Required supply demand gap inventory = cycle stock + supply demand gap safety stock

Inputs explained

Average daily unit consumption:
Replenishment lead time:
Safety stock cushion:

How to use the result

Use it during weekly S&OP reviews or whenever a supplier lead time changes, to check that on-hand stock still bridges the replenishment window.
It assumes steady, level daily usage; lumpy or seasonal demand can leave you short even when the average-based coverage looks healthy.

Current U.S. benchmarks

The producer price index for steel mill products stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 3,569 primary metal manufacturing establishments employing about 354,911 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate a supply-demand gap? Multiply daily usage by lead time to get cycle stock, add safety stock for the required inventory, then compare that against on-hand stock. With 1,200 units/day over an 85-day lead time, the coverage math yields about 12.83 protected days versus 14.12 unprotected days.
What does protected days of supply mean? It is the number of days your current on-hand inventory can cover average demand before it runs out. In the worked example that is 12.83 days, so anything beyond that window is exposed to a stockout unless replenishment arrives sooner.
What is the difference between cycle stock and safety stock? Cycle stock (usage times lead time) covers expected demand during replenishment, while safety stock is the extra buffer that absorbs demand spikes and supplier variability. The calculator sums both to size the required position.
What is a good supply-demand gap? Ideally the gap is zero or slightly positive, meaning protected days meet or exceed your lead time. A shortfall like 12.83 protected days against an 85-day lead time signals a serious replenishment gap that needs a purchase order or an alternate source.
How does lead time affect the gap? Longer lead times raise required cycle stock proportionally. Doubling an 85-day lead time doubles the cycle stock you must carry to hold the same protected coverage, which is why lead-time reduction is often cheaper than adding inventory.

Last reviewed 2026-05-12.