Combine harvester productivity for a 35 ft header at 5 mph and 80 percent efficiency is 16.97 acres per hour. In corn yielding 200 bushels per acre, that is 3,394 bushels per hour, so a 1,200 acre harvest takes about 71 hours of cutting time, or about 7 working days at 10 harvest hours per day.
How Combine Harvester Productivity Works
Acres per hour for a combine follows the same formula as every other field machine. Acres per hour equals header width in ft times speed in mph times efficiency divided by 8.25. Header width is the working width of the header, which is the width that actually cuts crop on each pass. Speed is the average ground speed held while cutting, not the top speed on the road or on a headland turn. Efficiency is the share of time spent cutting new ground at full width, after allowing for turns, unloading, adjustments and stops.
Use the harvesting acres per hour calculator to try your own numbers. It also works in hectares and tonnes. For the full method, read the how to calculate acres per hour guide.
Header width has the largest effect on the rate, because doubling the width doubles the acres per hour if speed and efficiency stay the same. Speed matters just as much in the arithmetic, but in practice speed is often limited by crop condition and by threshing capacity, so a wider header is usually the safer way to raise output. Efficiency is the number most plans get wrong. A large rectangular field with good logistics can run at 80 to 85 percent, while a small or awkward field can fall to 65 percent or lower, and that difference changes the harvest plan by days.
Acres Per Hour by Header Width
The table below uses the formula with realistic speeds and efficiencies for each header size. Larger headers run a little faster because they are normally paired with larger combines, but the speeds shown are still ordinary field speeds.
| Header | Speed | Efficiency | Acres per hour |
|---|---|---|---|
| 20 ft | 4.5 mph | 75 percent | 8.18 |
| 25 ft | 4.5 mph | 75 percent | 10.23 |
| 30 ft | 4.5 mph | 75 percent | 12.27 |
| 35 ft | 5 mph | 80 percent | 16.97 |
| 40 ft | 5 mph | 80 percent | 19.39 |
| 45 ft | 5.5 mph | 80 percent | 24.00 |
Read the table as a planning range for combine harvester productivity, not as a promise. A 30 ft header at 4.5 mph and 75 percent gives 12.27 acres per hour, so a 600 acre field takes about 49 hours at that rate. At 65 percent efficiency it gives only 10.64 acres per hour, and the same 600 acres then take about 56 hours. The acres per hour chart by equipment puts these combine figures beside mowers, planters, sprayers and tillage tools.
Bushels Per Hour and Grain Handling
Bushels per hour equals acres per hour times yield in bushels per acre. This is the number that grain carts and trucks must keep up with, and it is often the real limit on harvest speed. A 35 ft header at 5 mph and 80 percent covers 16.97 acres per hour. In corn yielding 200 bushels per acre, that is 16.97 times 200, which equals 3,394 bushels per hour. In corn yielding 150 bushels per acre, the same combine covers 2,546 bushels per hour, because 16.97 times 150 equals 2,546. The acres per hour stays the same in both cases, but the grain flow falls by about a quarter, so the carts and trucks have an easier day in the lower yielding crop.
Work out combine harvester productivity in bushels per hour before harvest starts, then check it against cart capacity, truck cycle time and bin space. If the combine can cut faster than the grain can be moved, the combine will wait, and waiting time lowers the real efficiency for the whole day.
Unloading on the go with a grain cart keeps the combine moving and protects efficiency. Stopping at the field edge to unload costs minutes on every load, and those minutes add up across a long day. The cart also needs to be large enough and fast enough to clear the combine tank before it fills again. If the cart is late, the combine stops, and no header width can recover that lost time. Plan the cart and truck cycle as carefully as the combine rate, and keep the route from field to bin or truck as short as practical.
What Really Limits Harvest Speed
Threshing and separating capacity is often the first limit in high yielding crops. The header can gather crop faster than the threshing system can process it, and the first sign is rising grain loss behind the combine. When losses rise, slow down. A slower pass that keeps losses low is worth more than a fast pass that leaves grain on the ground. Lodged, tough or weedy crops force slower speeds, because the header and the threshing system both work harder in tangled material.
Unloading and field logistics are the second limit on combine harvester productivity. Distance to trucks or bins decides whether carts keep pace, and a long haul with too few trucks will hold the combine back even when the crop is standing well. Short passes mean more turns and lower efficiency. Weather and daylight set the outer limit, because morning dew, evening damp and rain breaks all cut into the hours available. Read the daily versus hourly productivity guide before setting a daily target.
Choosing a Header Width
A wider header raises combine harvester productivity in direct proportion, but it also needs a combine with enough threshing capacity to feed it, enough power to hold speed in heavy crop, and a trailer or road route that can move it between fields. A header that is too wide for the combine will force slower speeds, and the gain from the extra width can disappear into extra losses. A header that is too narrow wastes capacity that is already paid for, and the harvest takes more days than it should.
Match the header to the fields as well as to the combine. Wide headers suit large rectangular fields with long passes and few obstacles. Narrower headers suit small or irregular fields, where a wide header would spend more time turning than cutting. Gate widths, road widths and field entrances also matter. Measure them before harvest, not after the header arrives at a gate it cannot pass. The tractor and implement matching guide covers the same matching idea for tractors and implements, and the same thinking applies to a combine and its header.
Planning the Harvest Window
To plan combine harvester productivity, start with acres, divide by acres per hour to get cutting hours, then divide by harvest hours per day to get working days, then add days for weather. A 1,200 acre harvest with the 35 ft example takes 1,200 divided by 16.97, which equals 70.7 hours, about 7 working days at 10 harvest hours per day before weather. The same area with a 30 ft header at 12.27 acres per hour takes 97.8 hours, about 10 working days.
The table below shows working days at 10 harvest hours per day for three field sizes and two combine rates.
| Field size | Days at 16.97 acres per hour | Days at 12.27 acres per hour |
|---|---|---|
| 400 acres | 2.4 days | 3.3 days |
| 800 acres | 4.7 days | 6.5 days |
| 1200 acres | 7.1 days | 9.8 days |
Most areas lose some days to rain, so it is wise to plan for more calendar days than working days. Build in a buffer before the weather window closes, and cut the fields that are most at risk first. If the plan needs every day to be a full cutting day with no rain and no breakdowns, the plan is too tight. A realistic plan uses an efficiency figure that matches the fields, a daily hours figure that allows for dew and unloading, and a buffer of at least a few days for weather.
How to Raise the Real Rate Without Raising Losses
The safest gains in combine harvester productivity come from efficiency, not from speed. Plan long passes along the longest side of the field to cut the number of turns. Keep the grain cart close and unload on the go where it is safe to do so. Service the combine before the season so small failures do not stop work in the middle of a good day. Guidance cuts overlap and keeps passes straight. Read the understanding field efficiency guide for the full bands, from 55 to 65 percent on small fields up to 85 to 90 percent in ideal conditions. A gain in speed that raises losses costs grain on every acre, so it is a poor trade.
Common Mistakes in Combine Planning
The most common mistake in combine harvester productivity planning is to use the theoretical rate as the plan. It assumes the combine never stops, never turns and never unloads, and no real harvest works that way. Use the effective rate, which is the theoretical rate times efficiency, with an efficiency that matches the fields. The second mistake is to plan grain handling for acres per hour and forget bushels per hour. A high yielding crop moves far more grain per hour at the same acres per hour. The third mistake is to forget the weather buffer, and the fourth is to judge the combine only by header width. Threshing capacity, unloading, field shape and logistics all shape the real rate. Keep a simple log of acres, hours and yield for each field, so next season starts from real numbers instead of a guess.
Frequently Asked Questions
Q: How many acres per hour can a combine harvest?
A: It depends on header width, speed and efficiency. A 30 ft header at 4.5 mph and 75 percent covers 12.27 acres per hour, while a 40 ft header at 5 mph and 80 percent covers 19.39 acres per hour.
Q: How do I work out bushels per hour for a combine?
A: Multiply acres per hour by yield in bushels per acre. A combine covering 16.97 acres per hour in corn yielding 200 bushels per acre moves 3,394 bushels per hour.
Q: How long does it take to harvest 1,200 acres?
A: At 16.97 acres per hour it takes 70.7 hours, about 7 working days at 10 harvest hours per day before weather. At 12.27 acres per hour it takes 97.8 hours, about 10 working days.
Q: What limits combine speed most in high yielding crops?
A: Threshing and separating capacity often limits speed before the header does. If grain losses rise, slow down, because a slower pass that keeps losses low is worth more than a fast pass.
Q: Does a wider header always mean a faster harvest?
A: No. A wider header raises acres per hour only if the combine has enough threshing capacity and the grain handling can keep up. In small fields, a very wide header can lose its advantage to extra turning time.
Q: How much grain handling capacity do I need?
A: Plan it from bushels per hour, not from acres per hour. Work out acres per hour times yield, then check that carts, trucks and bin space can clear that flow without making the combine wait.
Combine harvester productivity is a chain, and the weakest link sets the pace. Work out the acres per hour and the bushels per hour, plan the carts and trucks for that flow, and leave room in the calendar for weather.
