Inventory Forecast Tool
Upload a sales history CSV and get a simple seasonal forecast and suggested reorder quantity per SKU, right in your browser.
How the forecast is built
Upload a file with one row per date, SKU and units sold (daily or monthly rows both work; the tool groups everything into months). For each SKU it takes a weighted average of the last three months, then adjusts it up or down if that same calendar month has history from a prior year.
Example: CANDLE-LAV from the sample file
- Last 3 months (weighted 1:2:3)
- Jun 158, Jul 152, Aug 160 → 157 units
- Same month last year (September 2025)
- 140 units vs. an overall average of 174 → index 0.80
Forecast for September 2026 = 157 × 0.80 ≈ 126 units. At a 30-day lead time plus 7 safety days, the suggested reorder quantity is 156 units.
This is a simple moving-average model with a light seasonal adjustment, not a statistical demand plan. It's a fast starting point for a purchase order, not a replacement for judgment: sanity-check any big swing by eye, especially for a SKU with under a year of history.
Your file
| Column | What it needs |
|---|---|
| Date | Any recognizable date. Daily or monthly rows both work. |
| SKU | Product name, SKU or variant title. Same spelling groups into the same series. |
| Units Sold | A plain number. Currency symbols and commas are stripped automatically. |
Export this from Shopify's Analytics → Reports → Sales by product (grouped by month), or WooCommerce's Analytics → Products report, and adjust the column headers to match if needed.
Questions people ask
How much sales history do I need?
At least 3 months for a basic moving-average forecast. At least 13 months (so the same calendar month appears twice) lets the tool apply a seasonal adjustment.
Does this replace a real demand planning tool?
No. It's a lightweight, honest starting point for smaller catalogs. If you're managing thousands of SKUs or complex promotions, a dedicated forecasting or inventory planning app will do better.
What if a SKU has no data for the month I'm forecasting?
The tool skips the seasonal adjustment for that SKU and forecasts from the recent moving average alone, flagged in the Note column.
Can I change the lead time and safety days?
Yes, both are editable options above the upload. They control the suggested reorder quantity, not the forecast itself.
Related tools
Want this builtinto your store?
I'm Emmanuel, a Shopify and WooCommerce developer. If this tool pointed at something you'd rather have fixed for you (a faster store, cleaner product data, a migration, a custom feature), send me a note.
Emmanuel Asika
Shopify & WooCommerce developer, Dublin
I build and fix online stores: new builds, migrations, speed, SEO and the custom bits apps can't do.
Last reviewed 30 September 2026.