Grain Cart Sizing Calculator

The cart's whole job is to buffer grain during the window when a truck is off hauling to the elevator and can't be under the combine — the minimum cart capacity is exactly total combine throughput multiplied by that round-trip cycle time. A longer cycle (more distance, elevator wait lines) means more grain accumulates with nowhere to go before the truck gets back, so cycle time drives the required cart size more directly than any other single input.

Total throughput is combine throughput per unit multiplied directly by the number of combines running simultaneously, and minimum cart capacity is total throughput times truck cycle time — so with two identical combines running the same field, both throughput and the resulting cart requirement scale close to linearly with the combine count, not sub-linearly. This is because both combines are dumping grain during the same truck-cycle window, not taking turns.

The minimum cart capacity is calculated assuming the truck cycle time you entered is met exactly every single time, with no slack for a truck running late or a longer elevator wait than usual. The 25% margin gives you buffer against that real-world variability so an occasional slow truck cycle doesn't force the combine to stop and wait for the cart to be emptied.

Since the minimum and recommended cart sizes scale directly with whatever cycle time you enter, plugging in your average cycle time only guarantees the combine keeps running on an average day — a longer-than-usual haul, traffic, or an elevator line will still overflow that capacity. Re-running the calculation with your worst realistic cycle time gives a cart sized to keep the combine going even on a bad day, not just a typical one.