Inventory how-to

How to track supplier lead times

Track lead time as the number of days from when you send a purchase order to when stock is receivable in your store.

Short answer: Track lead time as the number of days from when you send a purchase order to when stock is receivable in your store. Record it per supplier, and per SKU if times differ, and update it from actual order history rather than guessing or using what the supplier quotes.

Why lead time accuracy matters

Lead time sets your order-by date. If it is too short, you order late and run out. If it is too long, you order early and carry extra stock. Both cost you money, so the number needs to reflect reality, not the supplier's marketing promise.

What to measure

Measure from the day you send the order to the day the stock is in hand and ready to sell, not the day the supplier ships it. This captures transit time, customs delays, and any slow handling on their end. If a supplier is consistently slow or fast, your tracked number should move with that pattern.

Per supplier vs per SKU

Start with one lead time per supplier. If a supplier makes some items to order and stocks others, split those into separate lead times. The goal is a number you trust enough to set an order-by date from, not a perfectly granular record for every variant.

Keeping it current

Review lead times every few months, or after any order that arrives much earlier or later than expected. Suppliers change factories, shipping routes, and staffing, so a lead time that was accurate a year ago may not be accurate now.

Step by step

  1. List your suppliers and, for each, pull your last 5-10 purchase orders.
  2. For each order, note the date sent and the date stock was receivable in your store.
  3. Calculate the average and the worst-case (longest) lead time for each supplier.
  4. Use the average for routine reordering and lean toward the worst case for critical SKUs.
  5. Add a safety days buffer on top to cover variability, rather than inflating the lead time itself.
  6. Re-check these numbers after any late or early delivery, or at least quarterly.
  7. Keep the record in one place (spreadsheet or your inventory tool) so it does not live only in someone's memory.

Worked example

Riverside Supply Co. shipped three of your last four orders in 12, 14, and 11 days, and one took 20 days due to a customs hold. Your average lead time is about 12-13 days, but you set it at 14 days to account for the one slow order, and add 5 safety days on top. So your order-by trigger becomes daily sales x (14 + 5) days of coverage needed, which gives you a buffer without being as extreme as planning for the 20-day outlier every time.

How SteadyShelf helps

SteadyShelf lets you enter a lead time and safety days per supplier (or per SKU) and uses that to calculate each order-by date and reorder quantity automatically. It does not track shipment status or automatically detect that a supplier is running slow, so you still need to review and update the lead time number yourself based on how orders actually arrive.

$29/month flat, unlimited products and suppliers, 30-day free trial. Run the numbers now with the free reorder point calculator.

SteadyShelf is launching on the Shopify App Store. Join early access to get the install link first.

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FAQ

Should I use the supplier's quoted lead time or my own tracked number?

Use your own tracked number. Quoted lead times are often optimistic and do not account for your specific shipping route, order size, or the supplier's actual handling speed. Your own history is a more honest basis for reorder timing.

What if a supplier's lead time varies a lot between orders?

Lean toward the longer end of the range and increase your safety days rather than using the shortest lead time you have seen. This protects you from stockouts when an order happens to run slow, at the cost of carrying slightly more stock on average.

Let SteadyShelf do this math for every SKU

Order-by dates per supplier, seasonal forecasts and draft POs for your Shopify store. $29/month after a 30-day free trial.

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