How do you calculate days of inventory coverage?

Divide on-hand inventory by average daily demand for the raw figure, then divide by your reserve factor. With 1,200 units, 85 units/day demand and a 1.1 divisor, raw coverage is 14.12 days and protected coverage is 12.83 days.

What is the planning reserve divisor?

It's a safety haircut that converts optimistic coverage into a conservative number. A 1.1 divisor knocks the raw 14.12 days down to 12.83 days, building in a buffer against demand variability and lead-time slip.

What is a good days-of-coverage figure?

It depends on supplier lead time. You generally want protected coverage to comfortably exceed your replenishment lead time plus review cycle; if lead time is 10 days, the default's 12.83 protected days is tight but workable.

Why is protected coverage lower than raw coverage?

Raw coverage (14.12 days) assumes demand exactly matches your average. The reserve divisor deliberately shrinks it to 12.83 days so you plan against a worse-than-average scenario rather than getting caught short when orders surge.

Should the divisor be above or below 1?

Above 1 to be conservative — it reduces the coverage you plan against. A divisor of 1.0 means no buffer (you'd plan on the full 14.12 days), while 1.1 trims roughly 9% off to absorb variability.

How do I use coverage to set a reorder point?

Compare protected coverage against your lead time. If protected days fall to or below lead time, place the order. At 12.83 protected days, any lead time near or above that should trigger a reorder now.

Educational & Classroom Lab Equipment calculator

Classroom Lab Inventory Coverage Calculator

Education equipment demand is brutally seasonal — quiet in spring, then a wall of district orders before the school year. Knowing how many days of supply you're sitting on, and how that shrinks once you apply a planning buffer, tells inventory planners whether they can survive the next demand spike without expediting. This calculator turns on-hand units and average daily school-order demand into days of coverage, then applies a reserve divisor so you plan against a conservative figure rather than the raw best case. It's the metric that decides whether you reorder now or ride your current stock.

What this calculator does

Estimate days of inventory coverage for finished educational lab equipment, student kits, instruments, furniture components, consumables, or installation hardware.
Use it when classroom lab inventory coverage in educational and classroom lab equipment is being sized for a buffer or safety stock review.
Computes days of supply from on-hand inventory and daily demand, then divides by a reserve factor to give a conservative protected coverage figure.

Formula used

Raw inventory days of coverage = available educational equipment inventory ÷ average daily school-order demand
Adjusted inventory days of coverage = raw inventory days of coverage ÷ planning reserve divisor

Inputs explained

Available educational equipment inventory:
Average daily school-order demand:
Planning reserve divisor:

How to use the result

Use it during reorder reviews and seasonal demand planning to decide whether current stock spans the lead time ahead.
It uses a single average daily demand; for spiky back-to-school ordering, the average understates the risk during the peak, so pair it with a peak-demand check.

Current U.S. benchmarks

Steel mill PPI stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. New factory orders are up 2.3% year over year (Census).

Common questions

How do you calculate days of inventory coverage? Divide on-hand inventory by average daily demand for the raw figure, then divide by your reserve factor. With 1,200 units, 85 units/day demand and a 1.1 divisor, raw coverage is 14.12 days and protected coverage is 12.83 days.
What is the planning reserve divisor? It's a safety haircut that converts optimistic coverage into a conservative number. A 1.1 divisor knocks the raw 14.12 days down to 12.83 days, building in a buffer against demand variability and lead-time slip.
What is a good days-of-coverage figure? It depends on supplier lead time. You generally want protected coverage to comfortably exceed your replenishment lead time plus review cycle; if lead time is 10 days, the default's 12.83 protected days is tight but workable.
Why is protected coverage lower than raw coverage? Raw coverage (14.12 days) assumes demand exactly matches your average. The reserve divisor deliberately shrinks it to 12.83 days so you plan against a worse-than-average scenario rather than getting caught short when orders surge.
Should the divisor be above or below 1? Above 1 to be conservative — it reduces the coverage you plan against. A divisor of 1.0 means no buffer (you'd plan on the full 14.12 days), while 1.1 trims roughly 9% off to absorb variability.

Last reviewed 2026-05-12.