This page explains sales forecasting: using a style's own recorded sales from previous seasons to estimate how much of it will sell in the season ahead, rather than picking a reorder quantity from memory or hope. It is for a buyer or planner who must decide how many pieces of a continuity style to order next, before placing that order with a factory.
At work, a buyer such as Northline Apparel carries certain styles, like Order A's own T-shirt, season after season. Each time that style comes up for reorder, Northline's buyer must decide a quantity before the new season starts and before any of the new season's own sales exist yet. Guessing that quantity is a real problem: order too many and the surplus sits in shops until it is marked down; order too few and shops run out mid-season while demand is still there. This lesson gives you the method for turning a style's own sales history into a forecast a buyer can actually order against.
You need: no previous lesson in this course; general familiarity with how a buyer places a Make to Order order is useful background.
By the end of this lesson you can:
Not covered here: spreading a finished forecast across the weeks of a season (lesson 3.2); adjusting a forecast once real sales start coming in (lesson 3.3).
| Term | Meaning |
|---|---|
| Forecast | A company's own estimate of what it expects to sell, used to decide how much to produce before any specific sale exists. |
| Sales history | A style's own recorded sales from previous seasons, used as the starting point for estimating its future sales. |
| Weekly sales rate | The average quantity of a style actually sold per week, calculated from its own recorded sales history. |
| Continuity style | A style a buyer carries season after season, rather than a one-off style sold for a single season only. |
| Known change | A specific, identifiable reason a coming season's sales are expected to differ from the plain sales-history figure, such as more shops or a price change. |
| Forecast error | The difference between what a forecast predicted and what a style actually sold, once the season's real sales are known. |
A forecast is a company's own estimate of what it expects to sell, and for a continuity style the most reliable starting point for that estimate is the style's own sales history: what it actually sold in previous, comparable seasons. A buyer does not forecast a continuity style from a guessed number chosen without reference to real sales; it forecasts from the style's own recorded past, adjusted only where a specific, identifiable known change genuinely applies, such as Northline Apparel opening more shops or running the style in a different retail season.
| What can differ | The shapes you will meet | Why it matters |
|---|---|---|
| Export, Make to Order continuity | Northline Apparel forecasts Order A's own T-shirt from its shops' recorded sales in the previous three comparable seasons, before confirming a new order with Delta Garments. | A Make to Order buyer still forecasts before ordering; the order itself is confirmed once, but the quantity behind it is forecast first. |
| Domestic, Make to Stock | Cedar & Co. forecasts a basic style's monthly sales from its own 12 shops' recorded history to set a standing reorder quantity. | A domestic Make to Stock buyer forecasts continuously, since its own production runs against that standing forecast rather than one confirmed buyer order. |
| A style with a genuine known change | Northline Apparel opens two new shops partway through the previous season, so the T-shirt's own recorded sales history understates what a full season with all shops open will actually sell. | A known change must be identified and adjusted for specifically; it is not a reason to abandon the sales-history base altogether. |
| A style with no comparable history | A brand-new style with no previous season's own sales has no sales history to forecast from, and must instead be estimated from a comparable existing style until its own history exists. | The sales-history method applies fully only once a style has at least one genuine previous season behind it. |
Northline Apparel carries Order A's own T-shirt as a continuity style. Before confirming its next Make to Order order with Delta Garments, Northline's buyer pulls the style's own recorded sales from the previous three comparable seasons rather than guessing a quantity. The three seasons sold 13,200, 13,800 and 14,400 pieces respectively, a steady upward pattern rather than one unusually strong or weak season. Northline's buyer treats this real, recorded pattern as the forecast base, then checks whether any specific known change applies before finalizing the quantity behind the next order.
| Question | Guessing a reorder quantity | Forecasting from sales history |
|---|---|---|
| What does the buyer start from? | A round number chosen from memory or instinct | The style's own recorded sales across three real, comparable seasons |
| What happens if demand is genuinely steady? | The guess may happen to be close, or may not, with no way to tell in advance | The forecast reflects the style's own real, steady pattern directly |
| What happens if Delta Garments asks how the quantity was set? | The buyer has no recorded basis to point to | The buyer can show the three seasons' own sales history behind the number |
Northline Apparel's buyer averages the style's own sales across the three most recent comparable seasons to find its base weekly sales rate before applying any known change.
A common mistake is taking one recent season's own sales, especially an unusually strong one, and treating it as next season's forecast on its own. If Northline Apparel's buyer had forecast Order A's own T-shirt purely from its strongest season at 14,400 pieces, ignoring the two seasons before it, the forecast would sit above the style's own genuine average weekly sales rate, risking an order larger than the style's real, steady pattern supports, with the surplus resolved only through a markdown later in the season.
Before a buyer orders more of a style it already sells, it needs a real estimate of how much that style will sell next, not a guessed number. The most reliable estimate comes from the style's own recorded sales across several previous seasons, averaged to find its real weekly sales rate, and adjusted only for a specific, identifiable change that genuinely applies to the coming season. A forecast built this way can be explained and checked later; a guessed quantity cannot.
Northline Apparel's buyer has calculated Order A's own T-shirt average weekly sales rate at 13,800 pieces across the last three seasons. Two new Northline shops are confirmed to open one month into the coming season.
Should the forecast stay at the plain three-season average of 13,800 pieces, or be adjusted upward for the two new shops? Decide before you open the answer.
Adjusted upward, to about 14,413 pieces. The three-season average of 13,800 pieces is the correct forecast base, but the two new shops are a specific, known change that the sales-history figure alone cannot reflect, since neither new shop existed during the three seasons behind that average.
First, why the base figure understates the coming season. All three seasons behind the 13,800 average were sold through Northline's existing shop count; two more shops trading for part of the coming season adds real, identifiable demand the history does not contain.
Second, why the adjustment is shown as its own step. Two shops at roughly 460 pieces each for eight of twelve months is approximately 613 pieces (460 × 2 × 8 ÷ 12), an adjustment the buyer can explain and check later, not a rounded guess folded invisibly into the base number.
Northline Apparel's buyer should forecast approximately 14,413 pieces: the 13,800-piece history-based average plus the approximately 613-piece adjustment for the two new shops, with both figures kept visible in the worksheet. Lesson 3.2 takes this same forecast and spreads it across the weeks of the coming season.
Framed against the history-based forecast of 13,800 pieces: a guessed quantity that happens to land too high or too low carries a real, calculable cost either way.
A 1,400-piece guessing error above the history-based forecast, on a style whose own recorded sales support 13,800 pieces, converts directly into USD 5,572 of markdown cost once the surplus is cleared at Order A's own fixed 20% markdown rate. A guess that lands 1,400 pieces below the forecast instead loses the same 1,400 pieces of sales that the style's own history shows it can genuinely sell.
The workbook's "Sales history and forecast" sheet lists a style's own sales for its last three seasons, calculates the average weekly sales rate automatically, and provides a separate row for any known-change adjustment, so the base figure and the adjustment stay visible side by side rather than merged into one unexplained number.
Northline Apparel's own row records Order A's own three seasons at 13,200, 13,800 and 14,400 pieces, with the sheet calculating the 13,800-piece average and a separate adjustment row for the two new shops.
1. Why does a buyer forecast a continuity style from its own sales history rather than a guessed quantity?
2. Order A's own T-shirt sold 13,200, 13,800 and 14,400 pieces across its last three seasons. What is its base weekly sales rate before any known-change adjustment?
3. Two new Northline Apparel shops are confirmed to open one month into the coming season. How should this affect the forecast?
| EN | AR | FR | TR | Meaning |
|---|---|---|---|---|
| Forecast | التوقع (توقع المبيعات) | Prévision (prévision des ventes) | Tahmin (satış tahmini) | A company's own estimate of what it expects to sell, used to decide how much to produce before any specific sale exists. |
| Sales history | تاريخ المبيعات | Historique des ventes | Satış geçmişi | A style's own recorded sales from previous seasons, used as the starting point for estimating its future sales. |
| Weekly sales rate | معدل المبيعات الأسبوعي | Taux de vente hebdomadaire | Haftalık satış oranı | The average quantity of a style actually sold per week, calculated from its own recorded sales history. |
| Continuity style | طراز مستمر | Style de continuité | Sürekli stil | A style a buyer carries season after season, rather than a one-off style sold for a single season only. |
| Known change | تغيّر معروف | Changement connu | Bilinen değişiklik | A specific, identifiable reason a coming season's sales are expected to differ from the plain sales-history figure, such as more shops or a price change. |
| Forecast error | خطأ التوقع | Erreur de prévision | Tahmin hatası | The difference between what a forecast predicted and what a style actually sold, once the season's real sales are known. |
You now know how to build a forecast from a style's own sales history. The next lesson takes that same forecast and spreads it across the weeks of a selling season to match how the style actually sells. Back to the course map