| NCI Size Effect Mode, in cm (X0) | The mode of the size effect curve. |
| NCI Size Effect Variance, in cm (Xb) | The variance of the size effect curve. |
Size Effect is calculated as:

where:
| NCI Size Effect Mode, in cm (X0) | The mode of the size effect curve. |
| NCI Size Effect Variance, in cm (Xb) | The variance of the size effect curve. |
| NCI Size Effect Minimum Diameter | The minimum possible diameter for size effect. Trees with a diameter less than this value will use this value in the size effect calculation instead. |
Size Effect is calculated as:

where:
You can set a minimum diameter for the size effect in the NCI Size Effect Minimum Diameter parameter. Any target tree whose diameter is less than this value will get a size effect based on the minimum diameter instead. This allows you to avoid problems with very small trees that can occur because of the shape of the lognormal function.
| NCI Size Effect "a" | Size effect power function scaling factor "a" parameter. |
| NCI Size Effect "b" | Size effect exponent "b" parameter. |
Size Effect is calculated as:
where:
| NCI Size Effect Mode, in cm (X0) | The mode of the size effect curve. |
| NCI Size Effect Variance, in cm (Xb) | The variance of the size effect curve. |
| NCI Size Effect Shift, in cm (Xp) | The amount of peak shift. |
Size Effect is calculated as:

where:
| Size Effect "a" | The "a" parameter in the compound exponential function. |
| Size Effect "b" | The "b" parameter in the compound exponential function. |
| Size Effect "c" | The "c" parameter in the compound exponential function. |
| Size Effect "d" | The "d" parameter in the compound exponential function. |
Size Effect is calculated as:

where: