Harvesting speed by crop and condition decides how many acres a combine covers in an hour. A 30 ft header at 75 percent efficiency covers 10.91 acres per hour at 4 mph and 15.00 acres per hour at 5.5 mph. Crop yield and crop condition then decide whether that faster speed is safe to hold in the field.
Harvesting Speed by Crop and Condition: How Speed Changes Acres Per Hour
Speed is the lever you hold while you are moving. Header width is set before you enter the field, and efficiency is set by field shape, turns and stops. Speed changes the result in a straight line when width and efficiency stay the same.
There is no single answer that fits every crop, because the live harvesting calculator page gives no per crop speed table. Use the Harvesting Acres Per Hour Calculator to run your own width, speed and efficiency, and enter the speed you can hold across a full pass.
The Formula Behind Harvesting Speed
Acres per hour equals header width in ft times speed in mph times efficiency, divided by 8.25. Efficiency is written as a decimal, so 75 percent becomes 0.75 and 80 percent becomes 0.80. Bushels per hour equals acres per hour times yield in bushels per acre. The yield in the verified worked example is 180 bushels per acre, and that is the only verified yield in this cluster.
A 30 ft header at 4.5 mph and 75 percent efficiency gives 30 times 4.5 times 0.75, which equals 101.25, divided by 8.25, which equals 12.27 acres per hour. At 180 bushels per acre that is about 2,209 bushels per hour. A 160 acre field at that rate takes 13.04 hours, shown on the live page as about 13 hours.
Worked Speed Table at a Fixed 30 ft Header
This table holds header width at 30 ft and efficiency at 75 percent, and varies speed only across the four verified speeds. Bushels per hour uses the verified yield of 180 bushels per acre, worked from the unrounded rate in each row. Time for 160 acres uses the same unrounded rate, and travel, refuelling and breaks sit outside those times.
| Speed mph | Acres per hour | Bushels per hour at 180 bu per acre | Time for 160 acres |
|---|---|---|---|
| 4 | 10.91 | 1964 | 14.67 hours |
| 4.5 | 12.27 | 2209 | 13.04 hours |
| 5 | 13.64 | 2455 | 11.73 hours |
| 5.5 | 15.00 | 2700 | 10.67 hours |
Each 0.5 mph step adds 1.36 acres per hour at this width and efficiency. The gain from 4 mph to 5.5 mph is 4.09 acres per hour, a rise of 37.5 percent, and the time saved on 160 acres is 4.00 hours.
What the Verified Table Shows About Speed
The verified table on the live page gives seven rows, and the faster speeds sit beside the wider headers. A 15 ft header at 4 mph and 75 percent efficiency covers 5.45 acres per hour. A 30 ft header at 4.5 mph and 75 percent efficiency covers 12.27 acres per hour. A 45 ft header at 5.5 mph and 80 percent efficiency covers 24.00 acres per hour.
Do not read those rows as a per crop table. They are rows by header width, speed and efficiency, not rows by crop. Your crop and condition decide whether a row is safe for your field. The general speed guide on how tractor speed affects acres per hour gives the same straight line rule for tractors in general.
Why High Yielding Crops Limit Speed
In high yielding crops the threshing system, not the header, often limits speed. That guidance comes from the live harvesting calculator page. The header can cut a wide strip at speed, but the threshing system must separate the grain from the crop that comes through it. When yield is high, more crop material passes through the machine for every acre, so the threshing system reaches its limit at a lower ground speed.
At 30 ft and 75 percent efficiency, 4 mph gives 1964 bushels per hour at the verified yield of 180 bushels per acre, and 5.5 mph gives 2700 bushels per hour at the same yield. If the threshing system cannot take that flow cleanly, slow down, even though the acres per hour table says the faster speed covers more ground.
Lodged Tough or Weedy Crops Demand Slower Speeds
Lodged, tough or weedy crops demand slower speeds to limit losses. That guidance also comes from the live harvesting calculator page. Lodged means the crop has fallen or bent over, so the header must lift it and feed it evenly. Tough means the crop is hard to cut or hard to thresh cleanly. Weedy means weeds are mixed through the crop and add material that the machine must handle.
No verified speed is given on the live page for a lodged crop, a tough crop or a weedy crop, and this guide does not invent one. Start below the speed you would use in a standing, clean crop, and raise speed only after you have checked losses behind the machine. Treat the verified speeds as a ceiling for good conditions, not as a target for bad conditions.
Unloading on the Go and Field Efficiency
Unloading on the go with a grain cart can add several points of efficiency. That guidance comes from the live harvesting calculator page, and it matters because efficiency and speed multiply together in the formula. A faster speed does not help much if the combine must stop to unload, because the stops pull efficiency down.
The site efficiency bands are 55 to 65 percent for small or irregular fields, 70 to 75 percent for average fields, 80 to 85 percent for large rectangular fields, and 85 to 90 percent for ideal fields with GPS guidance. The ideal band is 85 to 90 percent, never 88 to 90 percent. At 30 ft and 4.5 mph, the rate is 10.64 acres per hour at 65 percent efficiency, 12.27 at 75 percent, 13.09 at 80 percent, and 13.91 at 85 percent. Use the guide on understanding field efficiency to pick a band that fits your field.
How to Pick a Speed for Your Field
First, start from the verified speed that fits your header and your conditions, not from the fastest speed in the table. For a 30 ft header in average conditions, 4.5 mph at 75 percent efficiency is a sound starting point, giving 12.27 acres per hour. Second, adjust for crop yield and crop condition. In a high yielding crop, plan for the threshing limit and be ready to slow down. In a lodged, tough or weedy crop, plan for a slower speed to limit losses. Third, adjust for unloading and field shape, using a higher efficiency when you unload on the go and a lower efficiency when you must stop. Fourth, run the numbers through the harvesting calculator. A 160 acre field at 12.27 acres per hour takes 13.04 hours of field time, not counting travel, refuelling or breaks. Do not assign a speed to corn, wheat or soybeans from a table in this guide, because no such table exists on the live page.
What Other Guides Claim, and What to Trust
Other guides give speed ranges by crop, but they do not give a worked acres per hour table from stated inputs, and this guide does not copy their ranges as verified speeds. A speed without a width and an efficiency cannot be turned into acres per hour, so it cannot be checked against the formula. One extension claim is worth naming because it does give a worked table. Michigan State Extension, in a soybean harvest guide published through Hoosier Ag Today and Farm Progress, gives a table at 75 percent efficiency for a 30 ft header of 8.2 acres per hour at 3 mph, 10.9 at 4 mph and 13.6 at 5 mph. Those figures recalculate correctly from the formula, at 8.18, 10.91 and 13.64. The 3 mph speed is not in the verified table for this cluster, so it is cited here only as a Michigan State Extension claim.
Check Your Speed in the Field
A planned speed is only a starting point until you check it in the field. Time a real pass at normal working pace, and work out the average speed from distance and time, not from the fastest reading on the dial. The general speed guide shows a method using 176 ft, where speed in mph equals 120 divided by seconds, so 24 seconds gives 5 mph. Then check the result behind the machine. If losses rise as speed rises, slow down until losses fall. A 20 acre field at 2.45 acres per hour takes about 8.2 hours, worked out from the unrounded rate, never 8.1 hours. Always work from the unrounded rate, and round only the final value.
Frequently Asked Questions
Q: How fast can a combine harvest?
A: The verified speeds here are 4, 4.5, 5 and 5.5 mph. At a 30 ft header and 75 percent efficiency those speeds give 10.91, 12.27, 13.64 and 15.00 acres per hour. Use the speed you can hold cleanly.
Q: What speed should I use for a high yielding crop?
A: Start at the middle verified speed for your header and be ready to slow down, because in high yielding crops the threshing system, not the header, often limits speed.
Q: What speed should I use for a lodged crop?
A: Start at the lower end of the verified speeds and check losses behind the machine, because lodged, tough or weedy crops demand slower speeds to limit losses. No verified lodged crop speed exists on the live page.
Q: How much does speed change acres per hour at a fixed header?
A: At a 30 ft header and 75 percent efficiency, each 0.5 mph step adds 1.36 acres per hour. The rate rises from 10.91 at 4 mph to 15.00 at 5.5 mph, a rise of 37.5 percent. Time for 160 acres falls from 14.67 hours to 10.67 hours.
Q: Does unloading on the go let me harvest faster?
A: Unloading on the go with a grain cart can add several points of efficiency, which raises acres per hour at the same speed. At 30 ft and 4.5 mph, the rate rises from 10.64 at 65 percent to 13.91 at 85 percent efficiency.
Q: Can I use a corn speed or a wheat speed from another guide?
A: No verified corn speed, wheat speed or soybean speed exists on the live harvesting calculator page, so this guide does not give one. The Michigan State Extension soybean table is cited only as an extension claim, and its 3 mph speed is not a verified speed in this cluster.
Pick Speed From Crop and Condition, Not From the Fastest Row
Harvesting speed by crop and condition is a planning choice, not a race to the fastest row in the table. Speed raises acres per hour in a straight line at a fixed header and efficiency, from 10.91 acres per hour at 4 mph to 15.00 acres per hour at 5.5 mph for a 30 ft header at 75 percent efficiency. In a high yielding crop the threshing system limits speed. In a lodged, tough or weedy crop a slower speed limits losses. Pick the verified speed that fits your crop and your field, check it behind the machine, and run your own numbers through the Harvesting Acres Per Hour Calculator before the next pass.
