Interactive tool · T-03
Trend Forecast
Fits a linear trend to a series of values, reports how well it fits and projects it forward.
- For
- Anyone tracking a measure over time — sales, output, costs or usage — who wants a first forecast.
- Service area
- Data & Analytical Solutions
- Privacy
- Runs in your browser. Nothing you enter is sent anywhere.
Your data
Separate values with commas, spaces or new lines. Equally spaced periods, for example one value per month.
Results
- Trend per month
- +6.08
- Fit (R²)
- 0.94
- Next month
- 170
- Values analysed
- 8
| Month | Forecast | 95% range |
|---|---|---|
| 9 | 170 | 157.5 – 182.5 |
| 10 | 176.1 | 162.7 – 189.5 |
| 11 | 182.2 | 167.8 – 196.6 |
The series changes by about 6.08 per month on average. An R² of 0.94 indicates a strong linear trend.
Why it matters
Seeing the underlying direction, and how reliable it is, is the first step before any detailed modelling.
How it works
The tool fits a straight line to your values by ordinary least squares, with the periods numbered 1, 2, 3 and so on. The slope is the average change per period.
R² is the share of the variation in your values that the line explains, from 0 to 1. The 95% range is a prediction interval: if the trend holds, each future value should fall inside it about 95% of the time.
Assumptions and limits
- Assumes the trend is linear and continues; it cannot anticipate turning points.
- Does not model seasonality. Monthly data with a strong seasonal pattern needs a seasonal model.
- Needs at least three values; the range narrows as more data is added.
- Periods must be equally spaced, with no gaps.