01
Enter average and maximum daily sales
Average daily sales sets the baseline lead time demand. Maximum daily sales (your busiest day in the past 90 days) determines the safety stock buffer.
Reorder Point Calculator
Calculate the exact inventory level to trigger your next order — no stockouts.
Updated Reviewed by Sajid Hussain· Editor
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Last updated
June 7, 2026
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9 markets · 8 currencies
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Never run out of stock again
Reorder point calculator — the exact level to trigger your next order
The reorder point (ROP) is the inventory level at which you must place a new purchase order to avoid running out of stock before the next shipment arrives. It combines the average demand during your lead time with a safety stock buffer that protects against demand spikes — giving you a single, reliable trigger number for every SKU.
Most sellers reorder by gut feel: "I am getting low, better order more." The result is either a stockout that kills ranking and revenue, or a panic overorder that ties up capital for months. A reorder point removes guesswork by giving you a precise trigger level based on your actual sales rate and supplier lead time.
The ROP formula uses two inputs: average lead time demand (how many units you normally sell while waiting for stock) and safety stock (a buffer sized to your maximum demand variability). Together they mean you will almost always have stock when the order arrives, even if demand spikes or your supplier ships a few days late.
Safety stock is calculated from the gap between your maximum and average daily sales, multiplied by lead time. If you always sell 10 units a day and never sell more than 15, the buffer is (15 − 10) × 30 = 150 units for a 30-day lead time. These 150 units protect you against a run of above-average selling days.
The days-until-reorder output tells you how long you have at your current stock level before you hit the trigger. Monitor it weekly — or daily for fast-moving SKUs — and reorder the moment you cross the ROP.
Quick facts
- Reorder point
- Lead time demand + safety stock
- Safety stock
- (max − avg daily sales) × lead time days
- Days until reorder
- (current stock − ROP) ÷ avg daily sales
- Stock on arrival
- Safety stock buffer you land with
- Below-ROP alert
- Flags when you need to order immediately
- Global
- Works for any channel, currency, or product type
How it works
Four inputs, one reorder trigger
Enter your sales rates, lead time, and current stock — your reorder point is ready in seconds.
02
Enter your lead time
How many days from placing your order to receiving stock. This is the window your current stock must cover before replenishment arrives.
03
Enter current stock
How many units you have on hand today. Used to calculate how many days until you hit the reorder point and whether you are already below it.
04
Read your reorder point
The calculator returns the exact unit level to reorder at, safety stock, lead time demand, and how many days until you need to act.
Steps to use the Reorder Point Calculator: Enter average and maximum daily sales, Enter your lead time, Enter current stock, Read your reorder point.
Formula
The reorder point formula, explained
Two components — average demand during lead time, plus a safety buffer for demand spikes. Simple math, powerful results.
01
Lead time demand
Lead Time Demand = Average Daily Sales × Lead Time Days
How many units you expect to sell at the average rate while waiting for stock to arrive. This is the minimum stock you need to hold at the time of reorder.
Example: 10 units/day × 30-day lead time = 300 units
02
Safety stock
Safety Stock = (Max Daily Sales − Avg Daily Sales) × Lead Time Days
The buffer above average demand that absorbs sales spikes during the lead time. Sized to the variability between your peak and average daily sales rate. Cannot go negative.
Example: (15 max − 10 avg) × 30 days = 150 units of safety stock
03
Reorder point
Reorder Point = Lead Time Demand + Safety Stock
The combined total: place your order the moment stock reaches this level. At average sales you will have safety stock remaining when the order arrives.
Example: 300 lead time demand + 150 safety stock = 450-unit reorder point
04
Days until reorder
Days Until Reorder = max(0, (Current Stock − Reorder Point) ÷ Avg Daily Sales)
How many days at the current average sell rate until you hit the reorder point. Zero means you should be ordering now.
Example: (600 current − 450 ROP) ÷ 10 avg/day = 15 days
Worked example
10 avg / 15 max daily units, 30-day lead time, 600 in stock
Watch a reorder point build from average sales and demand variability.
Scenario
A seller averages $10.00 units per day and has seen a daily peak of $15.00 units. Their supplier takes $30.00 days to deliver and they currently hold $600.00 units. When should they reorder?
1
Step 1 · Lead time demand
$10.00 avg units/day × $30.00 day lead time = 300 units expected to sell while waiting for the order.
Lead time demand: 300 units
2
Step 2 · Safety stock
Demand variability buffer: ($15.00 max − $10.00 avg) × $30.00 days = 150 units.
Safety stock: 150 units
3
Step 3 · Reorder point
300 lead time demand + 150 safety stock = 450 units. Order immediately when stock hits this level.
Reorder point: 450 units
4
Step 4 · Days until reorder
($600.00 current − 450 ROP) ÷ $10.00 avg/day = 15 days.
15 days to act
The takeaway
With 600 units on hand and a reorder point of 450, this seller has 15 days before they need to place the next order. When the new stock arrives, they will still have 150 units (the safety stock buffer) on hand — enough to cover above-average demand during any late-delivery scenario.
Industry benchmarks
Lead times and safety stock by sourcing region
Use these benchmarks to calibrate your lead time input and safety stock sizing. Lead times vary significantly by supplier location and shipping mode.
| Metric | Poor | Average | Good | Excellent |
|---|---|---|---|---|
Lead time — China by sea (FBA) Flexport Ocean Freight Index 2025 | > 60 days | 45–60 days | 30–45 days | < 30 days |
Lead time — India / South Asia Freightos Global Freight Index 2025 | > 50 days | 35–50 days | 25–35 days | < 25 days |
Lead time — Domestic / 3PL ShipBob eCommerce Fulfillment Report 2024 | > 14 days | 7–14 days | 3–7 days | < 3 days |
Safety stock coverage (days) APICS Supply Chain Management Reference 2024 | < 7 days | 7–14 days | 14–30 days | 30+ days (if margin permits) |
Demand variability (max/avg ratio) Gartner Supply Chain Survey 2024 | > 2.5× | 1.5–2.5× | 1.2–1.5× | < 1.2× (stable demand) |
Why this calculator
Calcrux vs spreadsheets vs Linnworks
Most sellers rely on ad hoc spreadsheets or expensive ERP tools that charge 200–500/month for inventory planning features. This calculator gives you the core reorder point formula free — including the safety stock buffer that most free tools omit.
| Feature | Calcrux | Manual spreadsheet | Linnworks (paid) |
|---|---|---|---|
| Reorder point formula (ROP) | Manual | ||
| Safety stock from max demand | Manual | ||
| Days until reorder | Manual | ||
| Stock on arrival estimate | Manual | Partial | |
| Below-ROP immediate alert | |||
| Long lead time warning | |||
| Works for any channel / marketplace | Ecommerce focused | ||
| Free to use, no subscription | |||
| No data connection required | |||
| Negative safety stock guard | Usually |
Common mistakes
Where reorder point calculations go wrong
Using only average sales without a peak demand buffer
Why it matters
If you set ROP purely on average demand during lead time (no safety stock), any week that runs above average during the lead time will cause a stockout. One unusually good week is enough.
Fix
Always add safety stock based on your max daily sales. The safety stock formula — (max − avg) × lead time — specifically covers the worst-case demand you have actually seen.
Using the wrong lead time — transit only, not total
Why it matters
Total lead time includes: supplier processing, international transit, customs clearance, and inbound to your warehouse or FBA. Using just transit time (the shipping leg) understates lead time by 1–3 weeks.
Fix
Measure total lead time from the moment you place the order to the moment units are available to sell. Track this over several orders and use the average, not the fastest.
Setting one ROP for the whole year regardless of season
Why it matters
A 10-unit/day average hides a 20-unit/day Q4 peak. The same ROP that protects you in January will cause a stockout in October when sales spike and lead time stays the same.
Fix
Recalculate your ROP for each season or quarter, or set your max daily sales to your seasonal peak. Many sellers maintain a separate "Q4 ROP" that they activate in September.
Ignoring supplier lead time variability
Why it matters
If your supplier sometimes takes 40 days instead of the stated 30, your ROP based on 30-day lead time is too low. A late shipment with a too-low ROP almost always causes a stockout.
Fix
Add lead time variability to your safety stock by measuring actual lead times over several orders. If your lead time swings 30–45 days, use 40 days as your planning figure.
Not monitoring days-until-reorder continuously
Why it matters
A reorder point is only useful if you know when you are approaching it. Checking stock once a month means you may already be below ROP before you notice.
Fix
Set up a weekly (or daily for fast movers) review of current stock vs ROP. Use the days-until-reorder output as a countdown — when it drops below 7 days, order immediately.
Using the same ROP for every SKU
Why it matters
A high-velocity SKU selling 50 units a day needs a very different ROP from a slow mover at 2 units a day, even with the same lead time. Blending them into one number loses all the signal.
Fix
Calculate ROP per SKU, especially for your top 20% of revenue drivers. Group slow movers into buckets by lead time and variability profile if you have too many SKUs to do each individually.
Tips
Getting the most from your reorder point
Pair ROP with order quantity
The reorder point tells you WHEN to order. Use the inventory forecast calculator to determine HOW MUCH to order — typically enough to cover your next planning cycle plus safety stock.
Update max daily sales quarterly
Your peak demand changes with growth, season, and promotions. A max daily sales figure from 12 months ago may dramatically understate or overstate your safety stock needs today.
Add FBA inbound processing time
For FBA, lead time is not just transit — add 3–7 days for FBA receiving and processing. A 30-day transit time plus 7 days FBA processing = 37-day effective lead time for your ROP.
Track actual vs predicted stockouts
If you stockout regularly despite following the ROP, your max daily sales or lead time inputs are understated. Track actual vs predicted and adjust quarterly.
Use ROP as last-resort floor
Think of the ROP as the emergency wire, not the planned trigger. Most sellers reorder well above the ROP to avoid cutting it close. The ROP is the latest you should order, not the ideal time.
Review slow movers for overstock
If a product has a very low daily sales rate, its ROP may be close to zero. This is fine — just pair it with a minimum order review so you do not carry holding costs on dead stock unnecessarily.
Use cases
When sellers use the reorder point calculator
The Reorder Point Calculator works across every stage of the workflow.
Ecommerce Operations Manager
An ecommerce ops manager sets the ROP for each SKU in their order management system. When stock hits the trigger, the system sends a purchase order automatically.
Amazon FBA Seller
An Amazon FBA seller monitors days-until-reorder weekly. When it drops to 14 days, they ship the next inbound from their 3PL to avoid the FBA processing delay.
Ecommerce Merchandising Manager
A home goods seller recalculates ROP every September to reflect Q4 peak demand, then resets to the baseline ROP in January once the season ends.
Ecommerce Product Manager
For a new product, a seller uses the first 3 weeks of sales to estimate average and max daily units, then sets a conservative ROP with high safety stock while demand patterns stabilize.
Procurement / Sourcing Manager
A buyer compares two suppliers: one at 15-day lead time (lower ROP, less capital tied up) vs one at 45 days (higher ROP). The ROP calculator quantifies the inventory investment difference.
Ecommerce CFO / Finance Lead
A CFO uses the ROP formula to estimate the minimum inventory capital requirement across the catalog — sum of all SKUs' reorder-point units × cost per unit gives the floor inventory investment.
Glossary
Reorder point vocabulary
Every important term you'll encounter in this calculator and the broader topic.
- Reorder point (ROP)
- The inventory level at which you must place a new order to avoid running out during the supplier lead time. ROP = lead time demand + safety stock.
- Lead time demand
- The units you expect to sell at the average daily rate during the supplier lead time. The minimum stock you must have when placing an order.
- Safety stock
- A buffer above the average lead time demand that absorbs demand spikes during the lead time. Calculated as (max daily sales − avg daily sales) × lead time days.
- Lead time
- Total days from placing a purchase order to units being available to sell — including supplier processing, transit, customs, and inbound receiving.
- Max daily sales
- Your highest actual daily sales in the past 90 days. Used to size the safety stock buffer.
- Stock on arrival
- Units remaining when the new order lands, assuming average daily sales throughout the lead time. Should equal your safety stock in normal conditions.
- Days until reorder
- How many days at the current average sell rate before stock hits the reorder point. When this reaches zero, order immediately.
- Stockout
- Running out of inventory before the next order arrives. On Amazon FBA, stockouts suppress search ranking and lose the Buy Box — often for days after restocking.
- Demand variability
- The swing between your average and peak daily sales. Higher variability requires more safety stock to protect against lead time stockouts.
Help & answers
Frequently asked questions
Everything you need to know about how the Reorder Point Calculator works.
01What is a reorder point?
The reorder point (ROP) is the inventory level at which you must place a new purchase order to avoid running out of stock before the next shipment arrives. It equals lead time demand (units sold during the lead time at average rate) plus safety stock (a buffer for demand spikes).
02How do you calculate the reorder point?
Reorder Point = (Average Daily Sales × Lead Time Days) + Safety Stock. Safety Stock = (Maximum Daily Sales − Average Daily Sales) × Lead Time Days. For example, if you sell 10 units/day on average (15 max) with a 30-day lead time: ROP = (10 × 30) + (15 − 10) × 30 = 300 + 150 = 450 units.
03What is safety stock in the reorder point formula?
Safety stock is the buffer inventory above average lead time demand that protects against demand spikes during the lead time. It is calculated as (max daily sales − average daily sales) × lead time days. Without safety stock, any week that runs above average during the lead time can cause a stockout.
04How do I find my maximum daily sales for the formula?
Look at your last 90 days of sales and find the single highest day. That is your max daily sales. For seasonal products, use the peak from the relevant season rather than an off-season low.
05What is the difference between reorder point and safety stock?
Safety stock is the buffer component — the extra units above average demand you keep to handle spikes. The reorder point includes both the safety stock AND the average demand during the lead time. ROP is the trigger level; safety stock is the built-in cushion within that trigger.
06What does "days until reorder" mean?
Days until reorder tells you how long — at your current average daily sales rate — before your stock hits the reorder point. It is calculated as (current stock − ROP) ÷ average daily sales. When it reaches zero or less, you should be placing an order.
07What is stock on arrival?
Stock on arrival is the number of units you expect to have remaining when the new order arrives, assuming average daily sales throughout the lead time. It should equal your safety stock — this is the buffer that separates you from a stockout even at average demand.
08How do I account for variable lead times in my ROP?
Use your maximum expected lead time (not the average) as your lead time input, or add extra safety days. If your supplier sometimes takes 45 days instead of the stated 30, use 40–45 days as your planning lead time to build a lead time buffer into the ROP.
09Does the reorder point calculator work for Amazon FBA?
Yes. For FBA, your lead time should include supplier processing + transit + FBA receiving (typically 3–7 additional days). If your supplier takes 30 days to ship and FBA takes 7 days to receive, use 37 days as your lead time.
10Should I use the same reorder point year-round?
No. Your ROP should reflect current demand. For seasonal products, recalculate it each quarter — especially before a peak season when your average and max daily sales rates are significantly higher than the off-season baseline.
11What if I am already below my reorder point?
Order immediately. Do not wait for a planned review cycle. A day below the ROP at average demand reduces your safety buffer — and if demand spikes while you are waiting, you risk a stockout.
12How is the reorder point different from the minimum stock level?
The reorder point is the trigger to place an order. The minimum stock level (or safety stock) is the buffer you aim to have remaining when the order arrives. The ROP includes both the transit demand and the safety buffer — it is always higher than the safety stock alone.
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Category
Ecommerce Seller Operations
Subcategory
inventory operations
Availability
Global · 9 markets
Price
Free forever
Topics
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