How Stockie's inventory forecasting works
Available on: Pro and above.
Stockie forecasts how fast each variant sells, then works out when you will run low and how much to order. It does that from your Shopify sales history - no forecast is guessed, and nothing is shared between stores.
Everything starts from one number: sales velocity.
Sales velocity
Sales velocity is average daily sales for a variant:
sales velocity = units sold in the lookback period ÷ days the variant was in stock
The second half is what makes it useful. Days when a variant was out of stock are removed from the divisor, because they are days you could not sell rather than days nobody wanted it. A product that sold 30 units in the 3 days it was available has a velocity of 10 a day, not 1 a day over a 30-day month.
Two consequences worth knowing:
- If a variant was out of stock for the entire lookback period, there are no days to divide by. Rather than showing a misleading zero, Stockie tells you the velocity is unavailable and forecasts nothing for it.
- If the variant is set to Continue selling when out of stock in Shopify, no days are excluded. It was sellable throughout, so the whole period counts.
What you control
Five settings shape every number on the page:
| Setting | What it does |
|---|---|
| Lookback period | How much sales history the velocity is measured over |
| Demand adjustment | Scales the velocity up or down by a percentage |
| Lead time | Days between ordering and stock arriving |
| Safety stock | Days of buffer held above forecast demand |
| Restock to | Days of cover you want after a delivery arrives |
The first two are covered in Configuring demand settings, the last three in Configuring reordering settings.
Where a variant has a min or max level at a location, those levels take the place of the forecast: the reorder point shows your min level and the suggested quantity is worked out from your levels. The row is marked Min/max.
What Stockie calculates
Reorder point - the stock level at which you should order:
reorder point = velocity × (lead time + safety stock)
At 5 units a day, a 14-day lead time and 30 days of safety stock, the reorder point is 220 units. Stockie flags the variant once your available and incoming stock together fall to it. There is no reorder point for a variant with no velocity, or where lead time or safety stock is unset.
Reorder in - how long until you hit that point, at the current velocity.
Stockout in - how long your stock will last, at the current velocity.
All of these count stock already on its way as well as what is on the shelf. A delivery you have ordered pushes the figures out as soon as Shopify shows it as incoming, before it arrives.
Suggested reorder quantity - how much to order:
suggested quantity = (restock to × velocity) + lead time demand - (available + incoming)
Lead time demand is what you expect to sell while waiting for the delivery. It is capped at the stock you hold or have on the way, so a variant with 40 units between them and 70 units of lead time demand contributes 40 - you cannot sell stock you do not have. The result is never negative and always a whole number.
What counts as a sale
Not everything in Shopify moves the forecast:
- Cancelled orders are excluded.
- Unpaid orders are excluded by default - anything Shopify shows as pending, voided or expired. This catches wholesale merchants out, because an invoiced draft order sits as pending until it is paid.
- Returns and refunds reduce the quantity counted against the original order.
When the forecast runs
The numbers on the page are a snapshot from the last forecast run, not a live view. Forecasts run once a day, and you can rebuild on demand with Run forecast.
After you change a setting, the page shows a Your forecast is out of date banner until the forecast runs again.
This is the single most common source of confusion with forecasting - see The forecast is a snapshot.
Where accuracy comes from
Stockie's arithmetic is only as good as what it is given:
- Lead times that match your deliveries. Every reorder point on a supplier's products moves with its lead time, so a figure based on recent deliveries tends to serve better than an ideal one.
- Enough history. A variant with two weeks of sales has a velocity built on two weeks of sales. It is not wrong, but it will move a lot as more history accumulates.
- Time to judge a change. A new setting shows up in the numbers after the next forecast runs, either overnight or when you choose Start new forecast, and it can take a few runs to see whether a new lookback period suits a product.
If a specific number looks wrong, Why do my forecast numbers look wrong? walks through the usual causes in order.