How do you calculate roll stock inventory days?

Divide roll stock on hand by average daily consumption. With 1,200 pieces on hand and 85 pieces per day of usage the unprotected coverage is about 14.1 days, and applying the safety-stock factor gives roughly 12.8 protected days.

What is the difference between protected and unprotected days?

Unprotected days is raw inventory divided by usage (about 14.1 days here). Protected days de-rates that coverage using your safety-stock factor to account for supply variability, giving the more conservative 12.8 days you should plan around.

What is a good number of days of roll stock to hold?

It depends on mill lead time. If the mill quotes 10-day replenishment you want protected coverage comfortably above that, so 12.8 days is a thin but reasonable buffer; long or unreliable lead times push planners toward 20-30 days.

How does the safety stock factor work here?

The factor scales your effective coverage down to reflect demand and supply uncertainty. A factor of 1.1 trims the raw 14.1 days to about 12.8 protected days, reserving roughly 10% of coverage as a cushion.

Should I calculate inventory days per grade or in total?

Per grade is far more accurate. A blended figure can look healthy while a specific liner or medium grade is about to stock out, so run it separately for each parent-roll grade that the corrugator burns.

Why hold roll stock inventory days instead of just a roll count?

A roll count means nothing without consumption context. Days of supply directly answers how long you can run and whether you will beat the next mill delivery, which is what schedulers actually need to decide.

Wood & Paper Manufacturing calculator

Roll Stock Inventory Days Calculator

Roll stock inventory days tells a corrugated or paper plant how many days of production its current supply of parent rolls will cover before a reorder is needed. Materials planners and corrugator schedulers use it to avoid the two costly failures of paper mills: running the corrugator dry and choking the warehouse with slow-turning rolls. Because parent rolls are bulky, expensive, and have long mill lead times, even a day or two of miscalculated coverage can idle the plant or blow the storage budget. It converts a raw roll count into an actionable days-of-supply figure.

What this calculator does

Estimate roll stock inventory days for wood and paper manufacturing using production-ready inputs so teams can plan replenishment and safety stock using actual usage and lead time.
Use it when roll stock inventory days in wood and paper manufacturing is being sized for a buffer or safety stock review.
It converts roll stock on hand and daily consumption into protected and unprotected days of supply, factoring in a safety-stock buffer.

Formula used

Roll stock inventory days cycle stock = roll stock inventory days daily usage × roll stock inventory days lead time
Required roll stock inventory days inventory = cycle stock + roll stock inventory days safety stock

Inputs explained

Roll stock on hand (pieces):
Roll stock daily consumption at the corrugator:
Safety stock factor for supply variability:

How to use the result

Use it at reorder-point reviews, before a mill shutdown, or when consumption shifts with a new order mix.
It assumes steady daily consumption; a lumpy order book or a grade change that shifts which rolls you burn can make the average days of supply misleading for any single grade.

Current U.S. benchmarks

The producer price index for lumber and wood products stands at 280.994 (BLS, May 2026), up 4.2% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The producer price index for paperboard and containers stands at 276.831 (BLS, May 2026), up 8.8% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 13,899 wood product manufacturing establishments employing about 432,255 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate roll stock inventory days? Divide roll stock on hand by average daily consumption. With 1,200 pieces on hand and 85 pieces per day of usage the unprotected coverage is about 14.1 days, and applying the safety-stock factor gives roughly 12.8 protected days.
What is the difference between protected and unprotected days? Unprotected days is raw inventory divided by usage (about 14.1 days here). Protected days de-rates that coverage using your safety-stock factor to account for supply variability, giving the more conservative 12.8 days you should plan around.
What is a good number of days of roll stock to hold? It depends on mill lead time. If the mill quotes 10-day replenishment you want protected coverage comfortably above that, so 12.8 days is a thin but reasonable buffer; long or unreliable lead times push planners toward 20-30 days.
How does the safety stock factor work here? The factor scales your effective coverage down to reflect demand and supply uncertainty. A factor of 1.1 trims the raw 14.1 days to about 12.8 protected days, reserving roughly 10% of coverage as a cushion.
Should I calculate inventory days per grade or in total? Per grade is far more accurate. A blended figure can look healthy while a specific liner or medium grade is about to stock out, so run it separately for each parent-roll grade that the corrugator burns.

Last reviewed 2026-05-12.