Combine Capacity Calculator

It's a pure unit-conversion factor, not an empirical adjustment: one acre is 43,560 square feet and one mph covers 5,280 feet per hour, so acres/hr = (speed × 5,280 × width) / 43,560, and that fraction simplifies exactly to speed × width / 8.25. This is the standard effective field capacity (EFC) formula published in ASABE D497, Agricultural Machinery Management Data, and it applies to any field operation measured in mph and feet, not just combines.

Tank fill time depends on bushels harvested per hour, not acres per hour — the calculator multiplies your acres/hour by yield to get bushels/hour, so a heavier crop fills the same grain tank faster even though you're covering ground at exactly the same rate. This is why tank fill time can vary a lot field to field even when your header, speed, and efficiency settings never change.

Field efficiency represents the fraction of time you're actually cutting grain versus turning at row ends, unloading, or dealing with downtime, and the calculator applies it directly as a multiplier on your theoretical acres/hour — combines typically run 60-75%, not 100%. Entering an optimistic number like 95% will overstate every downstream figure (bushels/hour, daily acres, daily bushels), so it's worth basing this on your actual field shape and how often you stop to unload or clear plugs.

Unloads per day is your tank fill time converted into a daily count — it tells you how many times the combine needs to transfer grain, either to a cart on the go or by stopping to unload into a truck. If that number comes back high relative to your available cart capacity or truck turnaround time, the combine is likely to sit idle waiting on logistics even though its raw harvest capacity looks fine on paper.