Source: https://oguzerol.com/en/sales-forecasting/ [ View full size](https://oguzerol.com/gorseller/senaryo/sales-forecasting-senaryo-en.webp) # Sales Forecasting | See What's Coming [Oğuz Erol](https://oguzerol.com/en/about-me/) | 4 min read | Published: 29 July 2026 | Updated: 13 October 2026 ## Quick summary A 3-6 month sales forecast built from your historical data, revealing seasonal patterns for stock and budget decisions. Seasonality separated from trend. Most SMBs forecast sales by gut feeling: “this month was good last year, so it’ll be good this year too.” Sometimes it holds up, sometimes it doesn’t. But the sales history you already have tells you more than you’d think — seasonality, growth trends, and recurring fluctuations are already written into it. In a sales forecasting engagement, I take your historical data, extract these patterns, and build a forecast band for the next 3-6 months. Not a single number — a likely range — because no forecast is ever certain, but it’s a far better basis for decisions than none at all. ## What Data Is Needed? Ideally, at least 18-24 months of monthly or weekly sales data. That’s the minimum needed to see a seasonal pattern repeat at least once. We can work with shorter data too, but the confidence interval comes out wider — I say that upfront. The data source can be your accounting software, your e-commerce platform’s sales report, or your POS system. The format doesn’t matter; as long as it’s a consistent date-amount series, we can process it. ## Separating Seasonal Patterns From the Growth Trend How much of your sales fluctuation comes from seasonality (summer months, pre-holiday spikes, year-end) and how much comes from actual growth or decline — mixing these two up leads to misleading conclusions. “This month dropped” might actually be growth once you compare it to the same month last year. The analysis separates these two components: the underlying trend line and the seasonal coefficients. That way you can see which month is genuinely weak and which is simply quiet because of seasonality. ## How the Forecast Turns Into Stock and Budget Decisions Once you have the forecast band, we tie it to inventory order timing, cash flow planning, and ad budget allocation. For example, knowing six weeks in advance that a busy month is coming makes your supply and stock decisions much easier. The forecast isn’t a one-time report — it’s a working document that needs updating as new data comes in. On first delivery, I also show you how to update it yourself. **How do we start?** First, we talk about what you want and what’s realistic. If it looks like a good fit, I send you the scope and price in writing, then we begin. You can reach me through the [contact page](https://oguzerol.com/en/contact/). ## Frequently Asked Questions ### My business is new and I don’t have much historical data — can you still forecast? To a limited extent. With less than a year of data, seasonality doesn’t come out reliably, and in that case we can produce a rougher forecast based on comparable industry patterns and general trends. But it really shows its strength once you have at least one full season of data. ### How accurate is the forecast? No forecast is ever 100% accurate, which is why I give you a range instead of a single number — something like “€150,000-180,000.” An unexpected event (a crisis, a currency shock, something going viral) can push actuals outside the forecast; that’s normal and not a flaw in the model. ### Does this help with my Google Ads budget planning? Directly, yes. Knowing your busy season in advance lets you shift budget into that period and save during quieter stretches. With 20 years of advertising experience, I can also offer to turn this forecast directly into a campaign calendar. ### How often should I update the forecast? Every 3 months is enough for most businesses. If you’re in a fast-growing or highly volatile sector, monthly updates work better. On first delivery, I leave you with a simple method you can use to update it yourself. [Back to top ↑](https://oguzerol.com/en/sales-forecasting/#icerik) ## You may also find these useful [Excel Sales Report Preparation and AutomationI combine store and online sales and returns files into an Excel report with defined totals, traceable sources and checks for missing or duplicate rows.](https://oguzerol.com/en/excel-sales-report/)[Basket and Cross-Sell Analysis | What Sells Together?Which products sell together? Your own sales data reveals cross-sell opportunities and bundle ideas you can act on right away. Bundle ideas come out of it.](https://oguzerol.com/en/basket-and-cross-sell-analysis/)[AI Data Analysis | Make Your Data TalkYour data doesn't fit a ready-made report? We define your question together, and I turn the data into a clear answer. We start with a sample.](https://oguzerol.com/en/ai-data-analysis/) [Browse all articles →](https://oguzerol.com/en/articles/)