The weight of steel bars of different diameters can be calculated using the formula for the weight of a steel bar per unit length, multiplied by the required length and the density of steel. The weight of a steel bar per unit length can be calculated using the formula:

Weight per unit length=π×Diameter2/4×Density of steel

Here, the density of steel is typically taken as 7850 kg/m³.

Let’s calculate the weights for the given diameters:

- For 16mm diameter bar: $Weight per unit length=π× /4×7850$
- For 12mm diameter bar: $Weight per unit length=π× ×7850$
- For 20mm diameter bar: $Weight per unit length=π× /4×7850$
- For 25mm diameter bar: $=π× /4×7850$
- For 8mm diameter bar: $Weight per unit length=π× /4×7850$

Using these formulas, we can calculate the weights per unit length for each diameter. If you provide the required length of the bars, I can then calculate the total weights for each diameter.