Inventory how-to

How to account for growth in your forecast

You account for growth by adjusting your daily sales rate upward before you calculate reorder points and order quantities, rather than just copying the last 28 days forward.

Short answer: You account for growth by adjusting your daily sales rate upward before you calculate reorder points and order quantities, rather than just copying the last 28 days forward. The safest way for a small store is a manual growth factor based on what you actually know is changing, not a guess about the future.

Why a plain sales-history average misses growth

A simple 28-day average tells you what happened recently, not what is about to happen. If you are growing, that average will always lag reality, and you will keep ordering slightly too little, run short, and reorder in a rush. The gap gets worse the faster you grow.

What actually drives growth you should plan for

Separate real, known drivers from hope. Known drivers: a new ad campaign starting, a wholesale account that just signed, a product getting listed somewhere new, last year's same-period growth versus the year before. Hope: "sales will probably keep going up." Only adjust your forecast for things you can point to.

Build a growth factor manually

Take your recent daily sales rate, then multiply it by a factor that reflects the known driver. If a new campaign historically lifts sales 20 percent, use 1.2x. If you have 13+ months of history and the same month last year grew over the year before, use that year-over-year ratio instead of a guess. Apply the factor to the daily sales number you use in your reorder point and order quantity formulas, not to the final order quantity alone, so lead time and safety days scale correctly too.

Recheck often while growth is live

A growth adjustment is a temporary override, not a permanent setting. Check actual sales against your adjusted forecast every week or two. If real sales are beating the adjusted number, raise the factor. If they are falling short, drop it back to the plain average. Growth phases are exactly when stockouts and overstock both get expensive, so short review cycles matter more than usual.

Step by step

  1. List any known upcoming driver of growth: campaign, new wholesale account, new listing, press.
  2. Pull your current daily sales rate from your normal sales window.
  3. Estimate a growth factor from past evidence, for example last year's same-period lift, not a hunch.
  4. Multiply daily sales by that factor to get an adjusted daily sales rate.
  5. Recalculate reorder point and order quantity using the adjusted rate, lead time, and safety days.
  6. Round the resulting order quantity up to the supplier's case pack and minimum.
  7. Review actual sales against the adjustment weekly and revise the factor up or down.

Worked example

Suppose a variant sells 10 units a day on average over the last 28 days, lead time is 14 days, and safety days are 5 days. Plain reorder point = 10 x (14 + 5) = 190 units. You know a campaign is launching that lifted sales 30 percent last time, so you apply a 1.3x growth factor: adjusted daily sales = 13 units. Adjusted reorder point = 13 x (14 + 5) = 247 units. If you are ordering for 30 days of cover with 50 on hand and 0 on order, order quantity = 13 x (14 + 30) - 50 = 572 - 50 = 522 units, then round up to the nearest case pack.

How SteadyShelf helps

SteadyShelf's forecast is built from your 28-day sales window, with seasonality applied once you have about 13 months of history, but it does not let you manually apply a growth multiplier for a known upcoming event. For a planned growth spike, calculate the adjusted daily sales rate yourself and treat the suggested order quantity as a floor, then round up manually before approving the purchase order.

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

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FAQ

Should I just increase my safety days instead of adjusting the growth factor?

No, these fix different problems. Safety days cover supply uncertainty like late shipments, while a growth factor corrects your demand forecast itself. If you only raise safety days, you are holding more buffer stock without actually forecasting the real sales level, which still leaves you short when growth kicks in hard.

What if my growth is uneven across variants, like one color selling faster than others?

Apply the growth factor per variant, not storewide. Check which SKUs are actually showing the lift and only adjust those daily sales rates. Applying one blanket factor across every variant will overorder the slow movers and still underorder the fast ones.

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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