Inventory Reorder Point Calculator

Check inventory inputs

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SKU or item:

Use a short SKU, product, ingredient, or spare-part label.

Average daily demand:

Use the expected daily pull for this SKU, not a peak day.

{{ unitLabel }}/day

Average supplier lead time:

Include supplier processing, transit, receiving, and put-away time.

days

Inventory position:

Enter stock you can count now and confirmed units already on order.

on hand

inbound

Safety stock method:

This changes how the buffer above lead-time demand is calculated.

Target service level:

Use 95% for many normal SKUs, and higher values for critical or slow-to-recover items.

Demand variability source:

Demand standard deviation:

{{ unitLabel }}/day SD

Usual daily demand range:

min/day

max/day

Demand volatility profile:

Lead-time variability source:

Lead-time standard deviation:

days SD

Usual lead-time range:

min days

max days

Supplier reliability profile:

Manual safety stock:

Use this when your planning policy already defines the buffer in units.

Max usage and lead time:

Use realistic historical peaks; one-off outliers can overstate reorder points.

max/day

max days

Target stock coverage:

Pick how many days of demand you want covered after replenishment, before the safety stock buffer.

days

Reserved or backordered units:

Include customer backorders, production allocations, or service tickets already committed.

Pack and minimum order:

Use 1 and 0 when the supplier lets you order exact units.

pack

MOQ

Review cadence:

Set to 1 for daily review or a larger number for weekly purchasing runs.

days

Stress-test adjustments:

Tune the stress ladder used in the result artifact.

demand %

lead %

Unit label:

Metric	Value	Basis	Copy
{{ row.metric }}	{{ row.value }}	{{ row.basis }}

Check	Status	Action	Copy
{{ row.check }}	{{ row.status }}	{{ row.action }}

Scenario	Status	Reorder point	Gap	Action	Copy
{{ row.scenario }}	{{ row.status }}	{{ row.reorderPoint }}	{{ row.gap }}	{{ row.action }}

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Referrer policy

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A buying decision has to happen while there is still stock left to sell, build with, or issue to a job. The reorder point is that trigger level: the inventory position where a new purchase order should be reviewed or placed before expected demand consumes the remaining supply during supplier lead time.

The trigger is not the shelf count by itself. Replenishment planning looks at usable on-hand stock, confirmed inbound supply, and units already reserved for customers, production, or service work. A SKU with 100 units on hand may be safe when 200 units are already inbound, or exposed when 90 units are committed and the supplier needs two weeks to replenish.

Lead-time demand: Expected units sold, consumed, or issued while waiting for replenishment.
Safety stock: Extra buffer held for demand spikes, supplier delay, forecast error, or receiving delays.
Inventory position: On-hand stock plus inbound supply, minus reserved or backordered units.
Target stock: The order-up-to level used to size the replenishment quantity after the trigger is reached.

Reorder points balance service and carrying cost. Higher triggers protect customers and production schedules, but they also keep more cash in inventory and can crowd storage space. Lower triggers reduce stock on hand, but they leave less room for late freight, supplier allocation, seasonal demand, or a promotion that moves faster than the historical average.

Lead-time demand and safety stock forming a reorder point compared with inventory position and target stock — Lead-time demand covers expected use while the order is in transit; safety stock protects against variation.

Small businesses, ecommerce sellers, spare-parts teams, and production planners often review reorder points SKU by SKU because each item has a different demand rate, supplier lead time, pack size, margin, storage limit, and shortage consequence. A fast-moving low-cost consumable may justify a higher service level than a slow, bulky item that can be expedited when needed.

A reorder point does not choose a supplier, negotiate a price, or prove that the forecast is right. It gives a disciplined trigger that still needs a reality check against seasonality, promotions, discontinued products, supplier holidays, minimum order quantity, and any purchase orders that are already late.

How to Use This Tool:

Start with the SKU's normal daily movement, then choose the safety-stock method that matches the data you actually have. The result is most useful when demand, lead time, inventory position, and supplier rounding all describe the same item and review period.

Enter SKU or item, Average daily demand, and Average supplier lead time. The summary should move from Check inputs to a replenishment status once demand and lead time are both above zero.
Fill in Inventory position with on-hand and inbound units. Open Advanced when reserved or backordered units should reduce the stock available for future demand.
Select a Safety stock method. Use Service level + variability when demand and lead-time history are available, Manual safety stock for a fixed policy buffer, or Max usage and max lead time when peak values are the only practical shortcut.
For the service-level method, choose the Target service level and provide demand and lead-time variation as standard deviation, usual min/max range, or a rough profile. If a range maximum is below its minimum, the calculator pauses with the matching validation message.
Set Target stock coverage, then use Pack and minimum order when suppliers sell only case packs or require a minimum order quantity.
Use Review cadence to flag SKUs that may cross the trigger before the next purchasing review. Tune Stress-test adjustments to test demand lift and lead-time stretch without changing the base inputs.
Read Reorder Trigger Table first, then check Order Plan Table, Stress Test Table, and Lead-Time Sensitivity Chart for warnings, rounded order quantity, and lead-time risk.

When the result looks surprising, check the Lead-time demand, Safety stock, Inventory position, and Planning warnings rows before changing the purchase order.

Interpreting Results:

Reorder point is the trigger level after lead-time demand and safety stock are rounded up to whole units. Inventory position is the value compared with that trigger. The most important line is Gap to trigger: a positive gap means the SKU is still above the trigger, zero means it is exactly at the trigger, and a negative gap means it has already crossed it.

Inventory reorder point status interpretation
Status	Condition	What to check next
`Monitor`	Inventory position is above the reorder point and not close enough to cross within the review cadence.	Keep the SKU on the normal buying review and watch demand changes.
`Review soon`	`Days until reorder point` is less than or equal to the review cadence.	Confirm supplier lead time and decide whether to prepare the purchase order early.
`Order now`	Inventory position is less than or equal to the reorder point.	Review `Immediate order quantity`, pack rounding, and supplier availability.
`Stockout`	Net available on-hand stock is zero or lower after reserved units are subtracted.	Escalate replenishment, customer commitments, and substitute options.

The order quantity is not only the gap to the reorder point. It is the amount needed to rebuild toward Target stock level, then rounded to supplier pack size and minimum order quantity. That is why a SKU can need 414 units by policy but show an Immediate order quantity of 420 units after case-pack rounding.

A green or monitor status does not prove the SKU is safe. Review On-hand runout, Lead-Time Sensitivity Chart, and any Planning warnings when current promotions, supplier delays, or allocations are not represented by the historical inputs.

Technical Details:

Reorder point planning starts with expected consumption during lead time, then adds safety stock for uncertainty. The same inventory position can be safe or risky depending on demand speed, supplier lead time, service target, and how much variation is included in the buffer.

The service-level method uses a normal-curve z score and a combined variation term for demand and lead time. Manual safety stock bypasses the statistical buffer and uses the entered unit quantity. The maximum-usage shortcut compares peak lead-time demand with average lead-time demand, so it can become conservative when one unusual peak is treated as a normal planning condition.

Formula Core:

\begin{array}{lcl} LTD & = & D \times L \\ {SS}_{service} & = & z \times \sqrt{L \times σ_{D}^{2} + D^{2} \times σ_{L}^{2}} \\ ROP & = & ⌈ LTD + SS ⌉ \\ IP & = & OH + IN - R \end{array}

Reorder point formula variables
Symbol	Meaning	Units
`D`	Average daily demand	Units per day
`L`	Average supplier lead time	Days
`z`	Service-level z score	Standard deviations
`σ_D`	Daily demand standard deviation	Units per day
`σ_L`	Lead-time standard deviation	Days
`OH`, `IN`, `R`	On-hand, inbound, and reserved or backordered units	Units
`C`, `T`	Target coverage days and target stock level	Days and units
`P`, `MOQ`	Supplier pack size and minimum order quantity	Units

Range-based variability is converted to a standard deviation by dividing the usual high-minus-low range by 4. Rough demand profiles estimate demand standard deviation as 15%, 30%, or 50% of average demand for stable, typical, or volatile demand. Rough supplier profiles estimate lead-time standard deviation as 10%, 20%, or 35% of average lead time.

Safety stock method mechanics
Safety stock method	Mechanism	Main caution
Service level + variability	Uses the selected service-level z score with demand and lead-time standard deviations.	Normal-curve assumptions can understate risk for intermittent, skewed, or promotion-heavy demand.
Manual safety stock	Uses the entered buffer units directly.	A stale policy buffer can lag behind faster sales or longer supplier lead times.
Max usage and max lead time	Uses `max daily demand x max lead time - average lead-time demand`.	One unusual peak can push the reorder point higher than the SKU really needs.

Service level z score options
Target service level	z score	Planning implication
85%	1.04	Lower buffer for less critical or easily replenished SKUs.
90%	1.28	Moderate buffer when occasional stockout risk is acceptable.
95%	1.65	Common planning target for normal replenishment items.
97.5%	1.96	Higher buffer for harder-to-recover shortages.
99%	2.33	Large buffer for critical SKUs where stockouts are costly.

Order sizing uses a second set of equations after the reorder point is known. Target stock is the larger of the reorder point or the desired coverage demand plus safety stock. If the SKU has already crossed the trigger, the raw order closes the gap from current inventory position to target stock. If it has not crossed the trigger, the next-cycle order shows the quantity that would be bought when inventory position reaches the reorder point. A zero raw order stays zero; positive orders are rounded up to the supplier pack size after the minimum order quantity is applied.

\begin{array}{lcl} T & = & max (ROP, ⌈ D \times C + SS ⌉) \\ Q_{now} & = & max (0, T - IP) \\ Q_{next} & = & max (0, T - ROP) \\ Q_{rounded} & = & \{\begin{cases} 0 & if Q \leq 0 \\ ⌈ \frac{max(Q, MOQ)}{P} ⌉ \times P & if Q > 0 \end{cases} \end{array}

With the default service-level example, average demand is 18 units per day, lead time is 12 days, demand standard deviation is 6 units per day, lead-time standard deviation is 2 days, and the 95% service level uses a z score of 1.65. Lead-time demand is 216 units. The combined variation term gives about 68.6 units of safety stock, so the reorder point rounds up to 285 units. With 220 on hand, 80 inbound, and 15 reserved, inventory position is also 285 units, so the SKU is exactly at the trigger.

The Lead-Time Sensitivity Chart recalculates reorder point across shorter and longer lead times while holding the current inventory position as the comparison line. Treat it as a stress view, not a forecast. A supplier that becomes unreliable may also change demand patterns, freight choices, or order economics beyond the lead-time input alone.

Accuracy and Privacy Notes:

Reorder point output is only as strong as the demand, lead-time, and commitment data behind it. The calculator is useful for replenishment planning, but it should not replace supplier confirmation or planner review for critical, regulated, perishable, high-value, or customer-committed SKUs.

Historical averages can miss seasonality, promotions, new customers, supplier shutdowns, allocation rules, and discontinued products.
Safety-stock formulas assume the selected variation inputs describe future uncertainty well enough for the chosen service level.
Pack size and minimum order quantity affect purchasable quantity; they do not optimize freight, holding cost, price breaks, or cash flow.
The calculation runs in the browser. If you share a URL after changing values, the values carried in that link may be visible to recipients.

Worked Examples:

Service-level reorder at the trigger. A hand-soap refill SKU averages 18 units per day, has 12 lead days, uses a 95% service level, and has 6 units/day demand standard deviation plus 2 lead-time days standard deviation. With 220 on hand, 80 inbound, and 15 reserved, the Reorder point is 285 units and Inventory position is also 285 units. The status is Order now, and a target stock level of 699 units with 12-unit packs rounds the Immediate order quantity to 420 units.

Review soon before the trigger is crossed. A consumable moves 20 units per day with 5 lead days and 40 units of manual safety stock. If inventory position is 170 units, the Reorder point is 140 units and Gap to trigger is +30 units. At the current demand rate, Days until reorder point is 1.5 days; with a 2 day review cadence, the status becomes Review soon instead of Monitor.

Fixing a demand-range error. If Usual daily demand range is entered as 40 minimum and 20 maximum, results pause with Demand range maximum must be at least the minimum. Correcting the range to 20 to 50 units/day estimates demand standard deviation as 7.5 units/day. With 30 units/day demand, 7 lead days, 90% service level, 1 day lead-time standard deviation, and 260 inventory position, the Reorder point is 257 units and Gap to trigger is +3 units, so a weekly review cadence still flags Review soon.

FAQ:

Is reorder point the same as minimum stock?

Not always. Minimum stock is often a policy floor, while Reorder point is the replenishment trigger built from lead-time demand and safety stock.

Why include inbound units in inventory position?

Inbound units are already expected supply, so they count in Inventory position. If those purchase orders are late or uncertain, check On-hand runout and the lead-time stress results before relying on them.

Which safety stock method should I choose?

Use Service level + variability when demand and supplier history are available, Manual safety stock when policy already sets a buffer, and Max usage and max lead time for a conservative shortcut from peak values.

Why is the order quantity larger than the raw gap?

The recommended quantity rebuilds toward Target stock level and then rounds to Pack and minimum order. A supplier case pack or MOQ can make the purchasable order larger than the raw need.

What should I do with planning warnings?

Read the warning text before ordering. High demand variability, unstable lead time, or target coverage shorter than lead time plus review cadence can make the trigger too thin for the current SKU.

Can I use this for seasonal items?

Yes, but update Average daily demand, variation inputs, and stress-test percentages for the season being planned. Old averages can understate the Reorder point before a known demand peak.

Glossary:

Reorder point: The inventory position where replenishment should be reviewed or triggered.
Lead-time demand: Expected demand during the supplier lead time.
Safety stock: Buffer stock held for demand variation, supplier delay, or forecast error.
Inventory position: On-hand stock plus inbound supply minus reserved or backordered units.
Service level: The target chance of covering demand during the replenishment lead time without a stockout.
Target stock: The order-up-to quantity used to size replenishment after the trigger is reached.
MOQ: Minimum order quantity required by the supplier.

References:

Reorder Point Planning, Oracle Inventory Help.
Inventory Optimization Users Guide, Oracle.
REORDER POINT FORMULA: Inventory Management Models : A Tutorial, NC State Supply Chain Resource Cooperative, January 30, 2011.
SAFETY STOCK ANALYSIS: Inventory Management Models : A Tutorial, NC State Supply Chain Resource Cooperative, January 28, 2011.
The effect of lead-time variability: The case of independent demand, Journal of Operations Management, February 1986.

Inventory Reorder Point Calculator

Introduction

How to Use This Tool:

Interpreting Results:

Technical Details:

Formula Core:

Accuracy and Privacy Notes:

Worked Examples:

FAQ:

Glossary:

References: