How to Set Up Inventory Reorder Points for Your Shopify Store (Using Actual Sales Data)
Most Shopify merchants set reorder points once and never revisit them. They pick a number that felt right at the time, and then their business changes around it while the number stays fixed. Sales velocity increases, a supplier changes their lead time, a seasonal spike hits, and the reorder point that worked in February is dangerously wrong in November.
This guide walks through how to calculate reorder points properly, using your actual sales data instead of rough estimates, and how to keep those numbers current as your store grows.
What a Reorder Point Actually Is
A reorder point is the stock level at which you need to place a new order to avoid stocking out before the new inventory arrives. It is not your minimum stock level. It is the trigger that gives you enough lead time to reorder and receive new stock before you run out.
The reason most manually set reorder points fail is that they are calculated from an average, not from current reality. Your store from six months ago is not the same as your store today, and a reorder point calculated on six-month-old averages is unreliable.
The Basic Reorder Point Formula
The standard formula is:
Reorder Point = (Average Daily Sales x Lead Time in Days) + Safety Stock
Let's work through each part.
Average Daily Sales: Take the total units sold for a SKU over the last 30 days and divide by 30. This gives you your current average daily demand. The key word is "current." Using 90-day or 180-day averages smooths out recent trends that matter. If your product just started selling faster, a 90-day average will understate your real demand.
Lead Time: This is the number of days between when you place a purchase order and when the inventory is available in your fulfillment location. It includes the time your supplier takes to process and ship the order, plus transit time, plus any receiving and processing time on your end. If you are not tracking this number explicitly, you are guessing.
Safety Stock: This is a buffer to absorb variability in both demand and lead time. The simple approach is to calculate safety stock as a multiple of your daily demand. A common formula is:
Safety Stock = (Maximum Daily Sales - Average Daily Sales) x Lead Time
This accounts for the scenario where demand runs higher than average during your lead time window. If your product averages 10 units a day but has sold as many as 18 units in a day, your safety stock needs to cover that gap over your lead time period.
A Worked Example
Suppose you sell a product with the following stats:
- Average daily sales: 12 units
- Maximum daily sales (over the last 30 days): 22 units
- Supplier lead time: 14 days
Safety stock = (22 - 12) x 14 = 140 units
Reorder point = (12 x 14) + 140 = 168 + 140 = 308 units
When your stock level hits 308 units, you need to place a purchase order. If you have 400 units in stock, you have about a week of buffer before you hit the reorder trigger.
That calculation is straightforward for one product. The challenge is doing it accurately for 200-2,000 products, keeping the inputs current, and recalculating whenever sales velocity changes significantly.
Why Manual Reorder Points Break Down at Scale
The formula above assumes your inputs are accurate and current. In practice, maintaining those inputs manually creates three problems.
Sales velocity changes constantly. A product going viral on TikTok can triple its daily sales in 48 hours. A competitor running out of stock shifts demand to your listing. Seasonal demand approaches. Any of these can make your manually calculated reorder point dangerously stale within days.
Lead times are not as stable as you think. Suppliers change their processing times. Shipping lanes get congested. You switch to a new supplier with different turnaround times. If your lead time input is outdated, your reorder point is wrong in a direction you cannot see.
Spreadsheets do not alert you. Even if you calculate reorder points correctly and keep them current, you still have to check your spreadsheet against your current stock levels to know when to order. That means the system only works as often as you manually run the check. If you miss a week, and your sales velocity spiked during that week, you can stock out before you realize you crossed the trigger.
How to Make This Process Automatic
The right approach is to use a tool that calculates reorder points dynamically, based on current sales velocity data, updates them when velocity changes, and alerts you when you cross the trigger for any SKU.
This is what ML-based inventory forecasting tools do. Instead of applying a static formula to static inputs, they analyze your rolling sales history, detect velocity trends, account for seasonal patterns, and generate reorder recommendations that reflect what your store is actually doing right now.
Restockly connects to your Shopify or WooCommerce store and does this automatically. After connecting via OAuth (which takes about 60 seconds), it analyzes your full sales history and generates a prioritized restock list showing exactly which SKUs to order, how many units to order, and by what date. Each recommendation includes a plain-English explanation of the reasoning, so you can verify it makes sense rather than trusting a black box.
The Stockout Risk Dashboard shows every SKU's days-of-stock-remaining, sorted by urgency. Red means stockout is imminent. Yellow means order soon. Green means healthy. You can see the status of your entire catalog in one view without running a report or touching a spreadsheet.
For seasonal inventory, Restockly's Pro plan includes year-over-year seasonal pattern detection. Instead of trying to remember that you needed 3x your normal stock of a particular product last October, the system detects that pattern in your data and builds it into the recommendation automatically.
Keeping Your Reorder Points Accurate Over Time
Whether you use a tool or manage this manually, the most common mistake is setting reorder points once and treating them as permanent. Reorder points should be recalculated at least monthly, and more often if your sales velocity is volatile.
The inputs that need regular review:
Sales velocity: Pull the last 30 days of sales data, not 90 days. Recent data is more predictive than older data for products with growing or declining trends.
Lead times: Keep a running log of actual order lead times by supplier. If your supplier's average lead time has crept from 10 days to 16 days over the last six months, your safety stock calculation using 10 days is consistently underestimating risk.
Seasonality adjustments: If you are approaching a high-demand period, your reorder point formula should use demand forecasts for that period, not your current average. A product that sells 10 units a day in September might sell 35 units a day in December. The reorder point you need in October to be ready for December is much higher than your current average would suggest.
Minimum order quantities: Some suppliers have MOQs that affect your ordering economics. If your calculated reorder quantity is 80 units but your supplier requires a minimum of 200, you need to build that into your planning.
Getting Started
If you are managing inventory manually right now, the first step is applying the reorder point formula to your top 20 SKUs by revenue. Get those right before trying to systematize everything.
If you want to automate the whole process, Restockly's free Starter plan covers up to 50 SKUs with full dashboard access and AI recommendations for your top 10 products. You can have your first automated restock recommendations in under a minute after connecting your store. The Pro plan at $29/month extends AI recommendations to every SKU in your catalog with hourly data sync, seasonal detection, and dead stock alerts.
The math on preventing stockouts is simple. If your average order value is $75 and you sell 20 units a day of your top product, a single 3-day stockout costs you $4,500 in revenue. Preventing that one stockout pays for more than a year of the Pro plan.
FAQ
What is a reorder point in inventory management? A reorder point is the stock level that triggers a new purchase order. It is calculated to ensure the new inventory arrives before you run out, accounting for your average daily sales and supplier lead time.
How do I calculate reorder points for my Shopify store? Use this formula: Reorder Point = (Average Daily Sales x Lead Time in Days) + Safety Stock. Safety stock is calculated as (Maximum Daily Sales - Average Daily Sales) x Lead Time. You need accurate, current data for both inputs.
How often should I update reorder points? At minimum monthly, and more frequently if your sales velocity is changing. Products with accelerating or decelerating sales trends need reorder points recalculated as soon as the trend is detectable, not after it has already caused a stockout or overstock situation.
Can I automate reorder point calculations in Shopify? Shopify does not calculate reorder points natively. You need a third-party inventory tool. Restockly automates this with ML-based forecasting that recalculates recommendations based on current sales data, lead times, and seasonal patterns.
What is safety stock and how much should I keep? Safety stock is a buffer to absorb demand spikes and lead time variability. A practical calculation is (Maximum Daily Sales - Average Daily Sales) x Lead Time. The right level depends on your supplier reliability and how much demand variability your products see.