Is this calculator specific to Shopify?

The math is ecommerce-specific and works especially well for Shopify stores because it includes the costs Shopify merchants usually need to model: COGS, payment fees, shipping, returns, ad spend, inventory, conversion rate, or repeat purchases depending on the tool.

Should I use gross margin or contribution margin?

Use contribution margin when you are making advertising, discount, or growth decisions. Gross margin is useful, but contribution margin is stricter because it accounts for variable costs like payment fees, fulfillment, shipping, returns, and app costs.

Why does the tool use default values?

Defaults make the calculator useful immediately and show the shape of the result before you enter your own numbers. Replace them with your store's actual numbers before making a final decision.

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Inventory Forecast Calculator

Forecast days until stockout, reorder point, and purchase quantity from sales velocity, growth, lead time, and safety stock.

Inventory forecast calculator

Forecast stockout timing, reorder point, and suggested purchase quantity from daily sales, growth, lead time, and safety stock.

Current stock

Average daily sales

Expected sales growth

Supplier lead time

Safety stock

Forecast window

Days until stockout

30.8 days

Adjusted daily sales

27.6

Reorder point

856

Forecast demand

1,656

Suggested order

806

Reorder now Reorder before inventory falls below 856 units.

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About this tool

What this free tool calculates

Use this weekly for hero SKUs. It shows whether your current stock can survive supplier lead time and expected demand growth.

How to use the result

Adjusted daily sales equals current daily sales plus expected growth. Reorder point equals adjusted daily sales times lead time plus safety stock days.

When the reorder signal turns urgent, use the stockout cost calculator to compare normal replenishment against expedited freight.

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Why the calculator stays input-driven

This free ecommerce tool does not guess demand, scrape competitors, or invent benchmarks. Change the numbers to match your store, then use the result to decide whether a product, campaign, discount, or inventory move is worth doing.

Frequently Asked Questions

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