CalcLibrary

Reorder Point Calculator

Estimate when to place the next inventory order from your average usage, supplier lead time, safety stock, and current stock on hand. See the reorder threshold, whether you should reorder now, and how many days remain before you hit that threshold or stock out.

Examples

84 units/week, 5-day lead time, 20 units of safety stock, and 95 units on hand gives a reorder point of 80 units and about 1.3 days before the threshold is reached.

Reorder status
Reorder in 1.3 days
Reorder point
80 units
Days until reorder
1.3 days
Days until stockout
7.9 days
Buffer above reorder point
15 units

Current stock is still above the threshold. Weekly usage is converted to a daily rate before timing is estimated.

This is an estimate from the assumptions you enter. Real demand spikes, supplier delays, and stock inaccuracies can still cause earlier or later stockouts.

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Examples

How It Works

Formula

Dlead=ud×LD_{\text{lead}} = u_d \times L

ROP=Dlead+SROP = D_{\text{lead}} + S

treorder=C−ROPudt_{\text{reorder}} = \frac{C - ROP}{u_d}

tstockout=Cudt_{\text{stockout}} = \frac{C}{u_d}

Variables

udu_d

Average usage per day after any weekly-to-daily conversion(units/day)

LL

Supplier lead time in days(days)

DleadD_{\text{lead}}

Units expected to be used during lead time(units)

SS

Extra buffer you want left after covering lead-time demand(units)

ROPROP

Lead-time demand plus safety stock(units)

CC

Units currently on hand(units)

First convert usage to a daily rate when needed. Lead-time demand is that daily rate multiplied by lead time in days. Add safety stock to lead-time demand to get the reorder point.

If current stock is above the reorder point, the gap between the two is your remaining buffer. Dividing that buffer by the daily usage rate estimates how many days remain before the reorder threshold is reached. Dividing current stock by the same daily rate estimates how many days remain before stockout under the same steady-usage assumption.

Frequently Asked Questions

01What is a reorder point?
The reorder point is the stock level at which the next purchase order should be placed. It combines the demand you expect during supplier lead time with any safety stock you want to keep in reserve.
02Why is safety stock added on top of lead-time demand?
Lead-time demand estimates what you expect to use while waiting for delivery. Safety stock is the extra buffer you choose to carry in case demand runs hotter than normal or the supplier takes longer than usual.
03How does weekly usage work here?
If you enter weekly usage, the calculator divides that figure by 7 to get a daily rate for lead-time demand and all day-based timing outputs. The page keeps the weekly label visible so the conversion is easy to audit.
04What does “Reorder now” mean?
It means current stock is already at or below the calculated reorder point. That does not mean you are out of stock today; it means the remaining stock is no longer above the threshold you set for covering lead time plus safety stock.
05What does this calculator not do?
It does not choose an order quantity, optimize carrying cost, forecast seasonality, or guarantee zero stockouts. It is a straight-line timing estimate from the usage, lead time, safety stock, and stock-on-hand assumptions you enter.

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