Reorder Point Calculator

Ordering too late causes stockouts. Ordering too early ties up cash. The reorder point is the number that keeps you in between — the exact inventory level at which you should place your next purchase order so stock arrives before you run out. This free interactive calculator gives you that number instantly, based on your actual demand and lead time data.

What Is a Reorder Point?

A reorder point (ROP) is the stock level that triggers a new purchase order. When your on-hand inventory falls to this level, you place an order — and by the time that order arrives (after your supplier's lead time), you still have stock left. Without a defined reorder point, you're either ordering by gut feel or reacting to near-stockouts.

Reorder points matter most for fast-moving SKUs and products with long or variable lead times. A product that sells 5 units per day and takes 14 days to arrive needs a very different reorder point than one that sells 50 units per day and ships in 2 days.

Getting this wrong has real costs. Stockouts lose you the sale and often the customer. Excess inventory means tied-up working capital, higher storage costs, and the risk of dead stock if demand shifts.

The Reorder Point Formula

The standard formula used by inventory planners is:

Reorder Point = (Average Daily Demand × Lead Time) + Safety Stock

Where:

Average Daily Demand — the number of units you sell per day on average (use the last 30–60 days for best accuracy)
Lead Time — the number of days between placing a purchase order and receiving the goods at your warehouse
Safety Stock — a buffer to absorb demand spikes and supplier delays (enter 0 if you have none, but most merchants should carry some)

The result tells you: when your stock drops to this number, it is time to reorder. You can also enter your current stock level to see how many days you have left before you hit your reorder point.

Use the Free Calculator Below

Enter your average daily demand, supplier lead time, and safety stock. Optionally add your current stock level to see days until reorder. The calculator updates instantly as you type.

If you are unsure of your average daily demand, export the last 30 days of sales from Shopify and divide total units sold by 30. For safety stock, use our free safety stock calculator to calculate the right buffer for each SKU.

Step-by-Step Example

Here is a worked example for a Shopify merchant selling a mid-velocity product:

Average daily demand: 20 units/day
Lead time: 10 days
Safety stock: 50 units
Current stock: 350 units

Step 1 — Reorder Point: (20 × 10) + 50 = 250 units

Step 2 — Days until reorder: (350 − 250) ÷ 20 = 5 days

This means: set an alert at 250 units. With 350 units on hand today, you have roughly 5 days before you need to place a new order. When stock hits 250, your supplier has enough lead time to deliver before you run out — including the 50-unit safety buffer.

When to Update Your Reorder Points

Reorder points go stale. Recalculate whenever any of these change:

Demand shifts — a product enters a growth phase, seasonality kicks in, or a promotion drives a lasting uplift. Your 30-day average will catch this if you recalculate regularly.
Lead time changes — a new supplier, a change in shipping route, or supply chain disruption. Even a 2-day increase in lead time can shift your ROP significantly on fast-moving SKUs.
Safety stock changes — if you've recalculated your safety stock levels, your reorder points need updating too since ROP is built on top of safety stock.
New product launches — use conservative estimates for average demand until you have 30+ days of data.

A practical cadence: review reorder points monthly for your top 20% of SKUs by revenue, and quarterly for the rest.

Why Lead Time and Safety Stock Both Matter

Lead time and safety stock are the two biggest levers in your reorder point. Understanding how they interact helps you make better stocking decisions:

Longer lead time → higher ROP. If your supplier takes 21 days instead of 7, you need to hold 3× more demand coverage before reordering. Shortening lead times (closer suppliers, faster shipping) directly reduces working capital requirements.
Higher demand variability → higher safety stock → higher ROP. Products with predictable, steady demand need less safety stock than volatile ones. Use the standard deviation of daily demand to size safety stock properly.
Zero safety stock is a choice, not a default. Some merchants run zero safety stock on slow-moving or low-margin items where holding cost exceeds stockout cost. That is a valid trade-off — but it should be deliberate.

For a deeper dive on sizing safety stock correctly, see our safety stock calculator and formula guide.

Frequently Asked Questions

What is a good reorder point?

There is no universal number — it depends entirely on your demand rate, lead time, and safety stock. The formula above gives you a statistically grounded ROP for your specific situation. Use it per-SKU rather than applying a blanket rule across your catalogue.

What if my lead time varies?

Use your average lead time for the base calculation, and fold lead time variability into your safety stock instead. Our safety stock calculator uses the standard deviation of demand to size the buffer — this implicitly handles some lead time variability as well.

Should I include safety stock in my reorder point?

Yes, almost always. Safety stock without a properly set reorder point is useless — you will dip into it on every replenishment cycle. The reorder point formula already accounts for safety stock by adding it on top of the demand-during-lead-time figure.

How often should I recalculate reorder points?

Monthly for top SKUs, quarterly for everything else. If you have a large catalogue, automate the calculation in your inventory system or use Verve AI to recalculate continuously based on live Shopify data.

Can I use this for multiple SKUs?

The calculator is designed for one SKU at a time — run it for each product separately. For large catalogues, consider our free demand forecasting Excel template which includes a multi-SKU reorder point table.