Reorder Point Calculator (Free): Formula + When to Reorder
Enter your average daily sales, lead time, and safety stock below. The calculator returns the exact inventory level at which you should place your next purchase order — the moment stock drops to this number, reorder.
Quick Answer
Your reorder point = (average daily sales × lead time in days) + safety stock. When on-hand inventory falls to that number, place your next order. It is the trigger level that covers demand during the wait for replenishment, plus a buffer for the unexpected.
Example: if you sell 20 units/day, your supplier lead time is 30 days, and you hold 150 units of safety stock, your reorder point is (20 × 30) + 150 = 750 units. Use the calculator below to run your own numbers.
Reorder Point Calculator
Type your numbers — the result updates instantly. Nothing is stored or sent anywhere.
Reorder when on-hand stock drops to this level. Lead-time demand here is 600 units; the rest is your safety buffer.
The reorder point formula
A reorder point (ROP) is the inventory level that triggers a new purchase order. The simple, industry-standard formula is:
Reorder Point = (Average Daily Sales × Lead Time) + Safety Stock
Each piece answers a specific question:
- Average daily sales — how fast you sell the SKU. Use a recent, representative window (often 30–90 days). Spiky products need a longer window or seasonality adjustment.
- Lead time — the full days from placing the order to the unit being sellable. For Amazon FBA that means manufacturing + freight + customs + Amazon receiving and check-in, not just the supplier's quoted production time.
- Safety stock — the buffer that absorbs demand spikes and lead-time delays. If you set safety stock to 0, your reorder point equals raw lead-time demand and you will stock out roughly half the time a delay or spike occurs. (Need to size this? Use our free safety stock calculator.)
The first term — average daily sales × lead time — is your lead-time demand: the units you'll sell while waiting for the new order to arrive. Add safety stock on top and you have the level at which you must reorder to avoid running dry before replenishment lands.
Worked example
A 20-units/day Amazon FBA SKU
Say you sell a kitchen product at a steady 20 units per day. Your supplier produces in 14 days, ocean freight + customs is another 12 days, and Amazon takes about 4 days to receive and make units sellable — a 30-day total lead time. You hold 150 units of safety stock.
| Average daily sales | 20 units/day |
| Lead time (production + freight + receiving) | 30 days |
| Lead-time demand (20 × 30) | 600 units |
| Safety stock | 150 units |
| Reorder point | 750 units |
The moment this SKU's on-hand inventory drops to 750 units, you place the next purchase order. The 600 units of lead-time demand carry you through the 30-day wait; the 150-unit buffer covers a freight delay or a demand bump without a stockout.
When the simple formula breaks
The formula above is correct — and it's enough for a single SKU on a single channel with steady demand and a reliable supplier. It quietly fails in three common situations every growing seller hits:
Multi-channel demand
If the same SKU sells on Amazon FBA, Shopify, and Walmart out of one pool of inventory, "average daily sales" has to be the combined velocity across every channel — and each channel can spike independently. Plug in only your Amazon number and your reorder point is too low; you'll stock out on the channels you forgot to count.
Variable lead time
The formula assumes one fixed lead time. Real supply chains vary: a 30-day lead time that occasionally stretches to 45 means your reorder point should be built around a realistic maximum, not the average. This is exactly the variability that proper safety stock is meant to absorb — and why a flat buffer guessed by feel is so often wrong.
Seasonality and trend
Using a trailing 30-day average for a Q4 product means you reorder against summer velocity right as demand triples. A static reorder point can't see the curve coming. Seasonal SKUs need their average daily sales projected forward, not pulled flat from the recent past.
How SKU Compass automates this per-SKU, per-channel
A calculator is great for one SKU on a slow afternoon. It does not scale to 500 SKUs across three channels that each move every day. SKU Compass runs this exact math automatically for every SKU, and fixes the three failure points above:
- Combined channel velocity. It pulls real sales from Amazon FBA, Shopify, and Walmart and computes average daily sales across all of them — not one channel in isolation.
- Lead-time-aware reorder points. Per-SKU lead times (including Amazon receiving time and AWD-to-FBA replenishment) feed the reorder math, so the trigger reflects your real supply chain, not a quoted production number.
- Dynamic safety stock and seasonality. Buffers are sized from actual demand and lead-time variability per SKU, and velocity tracks the trend — so reorder points rise ahead of a seasonal ramp instead of lagging it.
The result is a live reorder point for every SKU that you don't have to recompute by hand. For the concept and definition behind the trigger, see what is a reorder point.
Honest caveat: we built SKU Compass
We make inventory-forecasting software, so we're not a neutral party — take the pitch above with that in mind. The formula and the calculator on this page are the genuine, standard reorder-point math; they work whether or not you ever pay us a cent, and we'd rather you use them than guess.
The honest line: if you run a handful of SKUs on one channel with steady demand, this calculator (or a spreadsheet) is all you need — don't buy software for that. SKU Compass earns its keep once you're juggling many SKUs across multiple channels with variable lead times and seasonality, where doing this by hand stops being realistic.
Frequently asked questions
What is the reorder point formula?
The reorder point formula is (average daily sales × lead time in days) + safety stock. The first term is lead-time demand — the units you'll sell while waiting for replenishment — and safety stock is the buffer that protects against demand spikes and lead-time delays. When on-hand inventory drops to the resulting number, you place your next order.
How do I calculate a reorder point?
Multiply your average daily sales by your total lead time in days to get lead-time demand, then add your safety stock. For example, 20 units/day × 30 days = 600, plus 150 units of safety stock = a reorder point of 750 units. Use the free calculator above to run your own figures instantly.
What is the difference between reorder point and safety stock?
Safety stock is a buffer of extra units that protects against the unexpected; the reorder point is the inventory level that triggers a new order, and it includes safety stock plus the demand you expect during lead time. Safety stock is one input to the reorder point, not a synonym for it. You can size safety stock with our safety stock calculator.
Should I include safety stock in my reorder point?
Yes, for almost every real-world SKU. If you set safety stock to zero, your reorder point only covers expected demand during a perfectly on-time lead time — meaning any delay or demand spike causes a stockout. Safety stock is what makes the reorder point resilient to variability. The exception is a made-to-order or zero-buffer model where stockouts are acceptable.
What lead time should I use for Amazon FBA?
Use the full time from placing the purchase order to units being sellable on Amazon — manufacturing + freight + customs + Amazon's receiving and check-in time — not just the supplier's quoted production time. FBA receiving can add days or weeks, and leaving it out makes your reorder point too low. If you use Amazon AWD, also account for AWD-to-FBA replenishment time.
How is reorder point different from reorder quantity?
The reorder point tells you when to order (the trigger level); the reorder quantity tells you how much to order. They're separate calculations — reorder quantity is usually driven by economic order quantity (EOQ) or a restock-to-target policy that balances ordering cost against holding cost. This calculator gives you the trigger, not the order size.
Does the reorder point change over time?
It should. Average daily sales, lead times, and demand variability all move, so a reorder point set once and never revisited goes stale — especially for seasonal products, where a trailing average reorders against the wrong velocity. Recalculate regularly, or use software that recomputes it per SKU as your data updates rather than leaving a static number in a spreadsheet.
Can I use one reorder point if I sell on multiple channels?
Only if you base average daily sales on combined velocity across every channel that draws from the same inventory pool. The single-SKU formula doesn't care how many channels you sell on — but if you plug in just your Amazon number while also selling on Shopify and Walmart, the reorder point is too low and you'll stock out. This multi-channel demand aggregation is the main thing automated tools like SKU Compass handle that a single-input calculator can't.