How do you calculate protected days of supply?

Divide inventory on hand by daily usage, then adjust by the safety factor. With 1,200 units on hand, 85 used per day, and a 1.1 factor, the protected figure works out to about 12.83 days of supply.

What is the difference between protected and unprotected days?

Unprotected days is simply inventory divided by daily usage — here 1,200 / 85 = 14.12 days. Protected days applies the safety factor to give a more conservative 12.83 days you can actually promise against.

What is a good number of days of supply for a stone shop?

Most shops target 10-15 days across the template-to-install pipeline. The 12.83 protected days in the example sits comfortably in that band, covering a typical fabrication lead time with room to spare.

Why is the protected number lower than the unprotected one?

The safety factor of 1.1 inflates effective demand to guard against variability, so the same inventory covers fewer confident days. That is intentional — it keeps you from promising dates the buffer cannot back up.

How does daily usage affect the result?

Higher throughput burns the buffer faster. At 85 units per day the 1,200 on hand lasts about two weeks; push daily usage up and the days-of-supply figure falls proportionally, tightening your reorder timing.

Lead time vs days of supply — what is the relationship?

Days of supply must exceed your template-to-install lead time or jobs stall. If fabrication takes 10 days and you carry 12.83 protected days, you have a small cushion; if lead time creeps past your supply, reorder sooner.

Stone, Countertops & Engineered Surfaces calculator

Template-to-install lead time Calculator

Template-To-Install Lead Time gauges how many days of protected supply a countertop shop is carrying to cover the gap between templating a job and installing the finished tops. Scheduling managers and shop owners use it because the template-fabricate-install pipeline is where jobs stall — a missing slab or backordered edge profile blows the promised install date. By comparing stock on hand against daily throughput and the fabrication lead time, the tool shows whether you have enough buffer to keep crews and installers moving. It reports both a protected days-of-supply figure that includes your safety factor and the raw unprotected days, so you can see how much cushion the buffer actually buys.

What this calculator does

Estimate template-to-install lead time for stone, countertops and engineered surfaces using production-ready inputs so teams can plan replenishment and safety stock using actual usage and lead time.
Use it when template-to-install lead time in stone, countertops and engineered surfaces is being sized for a buffer or safety stock review.
It computes protected and unprotected days of supply from inventory on hand, daily usage, and a safety factor for the template-to-install pipeline.

Formula used

Template-to-install lead time cycle stock = template-to-install lead time daily usage × template-to-install lead time lead time
Required template-to-install lead time inventory = cycle stock + template-to-install lead time safety stock

Inputs explained

Slab and consumable stock on hand:
Template-to-install lead time:
Safety stock multiplier:

How to use the result

Use it when setting slab reorder points, promising install dates, or checking whether stock covers the fabrication lead time.
It treats usage as a steady daily average; seasonal demand spikes or a batch of large jobs will draw the buffer down faster than the model shows.

Common questions

How do you calculate protected days of supply? Divide inventory on hand by daily usage, then adjust by the safety factor. With 1,200 units on hand, 85 used per day, and a 1.1 factor, the protected figure works out to about 12.83 days of supply.
What is the difference between protected and unprotected days? Unprotected days is simply inventory divided by daily usage — here 1,200 / 85 = 14.12 days. Protected days applies the safety factor to give a more conservative 12.83 days you can actually promise against.
What is a good number of days of supply for a stone shop? Most shops target 10-15 days across the template-to-install pipeline. The 12.83 protected days in the example sits comfortably in that band, covering a typical fabrication lead time with room to spare.
Why is the protected number lower than the unprotected one? The safety factor of 1.1 inflates effective demand to guard against variability, so the same inventory covers fewer confident days. That is intentional — it keeps you from promising dates the buffer cannot back up.
How does daily usage affect the result? Higher throughput burns the buffer faster. At 85 units per day the 1,200 on hand lasts about two weeks; push daily usage up and the days-of-supply figure falls proportionally, tightening your reorder timing.

Last reviewed 2026-05-12.