Seasonal Adjustment Calculator — Formula
## How to Seasonally Adjust Data
### Formula
**Adjusted Value = Observed Value / Seasonal Index**
Seasonal adjustment removes predictable seasonal patterns from data, revealing the underlying trend. A seasonal index above 1 means the season inflates the value; below 1 means it deflates it. Dividing by the index normalizes the value as if there were no seasonal effect.
### Formula
**Adjusted Value = Observed Value / Seasonal Index**
Seasonal adjustment removes predictable seasonal patterns from data, revealing the underlying trend. A seasonal index above 1 means the season inflates the value; below 1 means it deflates it. Dividing by the index normalizes the value as if there were no seasonal effect.
Exemplo Resolvido
December sales are $150 with a seasonal index of 1.25 (holiday boost).
- Adjusted = 150 / 1.25 = 120
- Seasonal effect = 150 - 120 = 30
- The seasonal boost accounts for $30 (25%) of the observed value
- The underlying (de-seasonalized) value is $120