Lookback period
Lookback period defines how far back Stockie looks at historical sales data to calculate average daily demand.
It directly affects your:
- Daily sales rate
- Safety stock (units)
- Target cover (units)
- Lead time demand
- Suggested reorder quantities
Everything in forecasting starts with average daily sales — and lookback period determines how that number is calculated.
How lookback period works
Stockie calculates:
Average daily sales = total units sold during lookback ÷ number of in-stock days during lookback
Important:
Stockie excludes stockout days from the calculation.
This means days where inventory was zero (and sales were suppressed) do not dilute your true demand.
Example
If you select a 90-day lookback period and:
- You sold 450 units
- You were out of stock for 10 of those days
Then:
In-stock days = 80
Average daily sales = 450 ÷ 80 = 5.63 units per day
If stockout days were included, your daily sales would appear lower than reality.
Excluding stockout days helps ensure forecasts reflect actual demand — not lost sales.
Why stockout exclusion matters
Including stockout days can understate demand because:
- Customers cannot purchase what is unavailable
- Zero sales during stockouts do not mean zero demand
By excluding those days, Stockie estimates how the product sells when inventory is available.
This leads to:
- More accurate safety stock calculations
- More realistic reorder timing
- Reduced risk of repeating stockouts
How different lookback periods affect forecasts
Shorter lookback (e.g. 30 days):
- Responds quickly to recent changes
- Reacts faster to growth or decline
- More sensitive to short-term spikes
Longer lookback (e.g. 180 days):
- Smooths short-term volatility
- Reflects longer-term patterns
- Slower to react to rapid changes
There is no universally “correct” setting — it depends on your product and sales behaviour.
When to use a shorter lookback
Consider a shorter lookback if:
- The product was recently launched
- Demand is growing quickly
- You are testing new pricing or marketing
- Sales patterns changed recently
A shorter period keeps forecasts aligned with current performance.
When to use a longer lookback
Consider a longer lookback if:
- Sales are stable
- You want to smooth fluctuations
- The product has predictable long-term demand
A longer period reduces noise from temporary spikes or dips.