Grain Bin Aeration Calculator

Fan horsepower is Required CFM times Static Pressure divided by a fixed constant, and Target Airflow Rate feeds into both halves of that product -- it directly scales CFM, and it also drives Static Pressure sharply higher (not proportionally, but with an accelerating curve) because forcing air through packed grain faster takes disproportionately more pressure. That double effect is why Target Airflow Rate moves Fan HP more than Bin Diameter, Grain Depth, or Fan Efficiency across the calculator's declared ranges.

CFM per Sq Ft Floor is Required Fan CFM divided by the bin's floor area, and both of those scale with the square of Bin Diameter in exactly the same proportion -- so the diameter cancels out algebraically. What's left is just Grain Depth times Target Airflow Rate, which is why a wider bin needs more total CFM overall but the same airflow rate per square foot of floor.

A round bin's floor area scales with the square of its diameter, while grain depth only scales the stored volume linearly -- so across the calculator's declared ranges, widening the bin has a much larger effect on Bin Capacity (in bushels) than deepening the grain does. This mirrors real bin economics: going a size class wider adds far more storage than filling an existing bin a few feet deeper.

Air resistance through a packed grain bed doesn't scale linearly with airflow speed -- pushing air through faster takes disproportionately more pressure, similar to how it takes much more force to push water through a hose quickly than slowly. This calculator models that accelerating relationship, which is why doubling Target Airflow Rate more than doubles the resulting Static Pressure.

It assumes a fixed 200 hours of fan operation per year at a flat $0.12 per kWh rate, multiplied by the calculated Fan HP -- both of those assumptions are placeholders, not figures specific to your operation. Actual aeration fan run time varies widely by climate, grain condition, and whether you're cooling versus actively drying, and electricity rates vary by region, so treat this dollar figure as a loose approximation, not a bill projection.