Rotary cutter cost per acre falls when the cutter gets wider or the ground speed rises, because both levers raise acres per hour and cut the time charged to each acre. A 15 ft cutter costs about $16 per acre on average ground at the page example rate, against about $47 for a 5 ft cutter.
How Rotary Cutter Cost Per Acre Is Worked Out
Cost per acre equals hourly rate divided by acres per hour. That is the method the Bush Hogging Cost Calculator uses. Acres per hour equals cutter width in feet times speed in miles per hour times efficiency divided by 8.25. The figure 8.25 equals 43,560 divided by 5,280.
Efficiency is the part of a pass that cuts fresh ground at full width, once turns, overlap and stops are taken out. Small or irregular fields use 55 to 65 percent, average fields use 70 to 75 percent, large rectangular fields use 80 to 85 percent, and ideal fields with GPS guidance use 85 to 90 percent. The price table below uses Open at 80 percent, Average at 75 percent and Rough at 65 percent.
Work the page example once: a 20 acre pasture, a 6 ft cutter at 4 mph in average conditions at 75 percent, at an example rate of $85 per hour. First, 6 times 4 times 0.75 equals 18, and 18 divided by 8.25 equals 2.181818, shown as 2.18 acres per hour. Second, 20 divided by 2.181818 equals 9.166667 hours, shown as 9.2 hours. Third, the page price uses 9.17 hours times $85, which equals $779, and $779 divided by 20 equals about $39 per acre, both as example figures at the page example rate. The $85 rate is an example rate only, explicitly not a market rate.
The Width Lever: A Wider Cutter Covers More Ground in the Same Hour
Width moves acres per hour in direct proportion. Double the width at the same speed and efficiency and acres per hour doubles. Triple the width and acres per hour triples. The price moves the other way by the same proportion. Double acres per hour and the per acre price halves. Triple acres per hour and the per acre price falls to one third.
A 15 ft cutter is three times as wide as a 5 ft cutter, so it cuts three times as many acres per hour at the same speed and efficiency. At 4 mph and 75 percent efficiency, the 5 ft cutter cuts 1.8182 acres per hour and the 15 ft cutter cuts 5.4545 acres per hour. At the page example rate on average ground, the 5 ft cutter costs $47 per acre and the 15 ft cutter costs $16 per acre, both as example figures at the page example rate. A wide cutter needs a tractor that can carry it, so check the matching guide on bush hog width and tractor power matching before you plan a job around a 15 ft cutter.
The price table below shows that pattern across all five cutter sizes and all three terrain bands, all at 4 mph and the page example rate of $85 per hour. Every cell is an example figure at the page example rate, explicitly not a market price. For the general method see the live guide on bush hogging cost per acre.
| Cutter | Open at 80 percent | Average at 75 percent | Rough at 65 percent |
|---|---|---|---|
| 5 ft | $44 per acre | $47 per acre | $54 per acre |
| 6 ft | $37 per acre | $39 per acre | $45 per acre |
| 7 ft | $31 per acre | $33 per acre | $39 per acre |
| 10 ft | $22 per acre | $23 per acre | $27 per acre |
| 15 ft | $15 per acre | $16 per acre | $18 per acre |
Read the table down a column first. On average ground, the price falls from $47 to $39 to $33 to $23 to $16 as the cutter grows from 5 ft to 15 ft, all as example figures at the page example rate. On a 20 acre field, the $31 per acre gap between a 5 ft cutter and a 15 ft cutter is the gap between about $935 and about $312 in total at the page example rate, worked from unrounded rates. Across a row, a 6 ft cutter costs $37 per acre on open ground, $39 on average ground and $45 on rough ground, all as example figures at the page example rate.
The Speed Lever: Halving Speed Doubles Minutes Per Acre
Speed moves acres per hour in direct proportion too. Double the speed and acres per hour doubles. Halve the speed and acres per hour halves. Halve the speed and the per acre price doubles at the same hourly rate, because the same rate is now spread over half as many acres in the hour.
Minutes per acre equals 60 divided by acres per hour. A 6 ft cutter at 4 mph in average pasture cuts 2.1818 acres per hour, so 60 divided by 2.1818 equals about 28 minutes per acre. Halve the speed to 2 mph and acres per hour halves to 1.0909, so 60 divided by 1.0909 equals about 55 minutes per acre. At the page example rate on average ground, the 6 ft cutter costs about $39 per acre at 4 mph and about $78 per acre at 2 mph, both as example figures at the page example rate, worked from unrounded rates.
The table below shows the speed doubling rule across all five cutter sizes on average ground, at the page example rate of $85 per hour. Minutes are about figures, and prices are example figures at the page example rate, worked from unrounded rates.
| Cutter | Minutes per acre at 4 mph | Minutes per acre at 2 mph | Price per acre at 4 mph | Price per acre at 2 mph |
|---|---|---|---|---|
| 5 ft | About 33 | About 66 | $47 | $94 |
| 6 ft | About 28 | About 55 | $39 | $78 |
| 7 ft | About 24 | About 47 | $33 | $67 |
| 10 ft | About 16 | About 33 | $23 | $47 |
| 15 ft | About 11 | About 22 | $16 | $31 |
Every price at 2 mph is twice the price at 4 mph for the same cutter, within a dollar of rounding, because acres per hour halved and nothing else changed. A 10 ft cutter at 2 mph costs about $47 per acre at the page example rate, which is the same as a 5 ft cutter at 4 mph on the same ground. Speed and width trade against each other acre for acre.
Hours for a whole job double in the same way. The page example of 20 acres with a 6 ft cutter takes 9.2 hours at 4 mph in average pasture, and about 18.33 hours at 2 mph. A 15 ft cutter takes 3.67 hours at 4 mph and about 7.33 hours at 2 mph, both worked from unrounded rates. For the rate behind these prices, see the live guide on bush hog rotary cutter productivity, and for the 6 ft rate see the guide on how many acres a 6 foot bush hog cuts per hour. Thick brush may need 2 mph or less, and the live guide on how fast to bush hog thick brush covers safe speed in thick brush as a safety question, not as a price question.
When Both Levers Move Together: Wide on Rough Ground Still Beats Narrow on Open Ground
A 15 ft cutter on rough ground at 65 percent efficiency costs $18 per acre at the page example rate, while a 5 ft cutter on open ground at 80 percent efficiency costs $44 per acre at the page example rate. The wide cutter works the harder ground and still costs less than half as much per acre. It is three times as wide, so its acres per hour figure is three times as high before efficiency is applied. Rough ground pulls efficiency from 80 percent down to 65 percent, a drop of less than one fifth, so it cannot undo a threefold width advantage. Speed can undo a width advantage, because speed also moves in whole multiples: a 15 ft cutter at 2 mph on average ground costs about $31 per acre at the page example rate, while a 5 ft cutter at 4 mph costs about $47 per acre. For the widest cutter rate, see the guide on 15 foot bush hog acres per hour.
How to Use the Two Levers on Your Own Job
Start with the calculator, not with a per acre figure from another page. Enter the acreage, the rotary cutter width and a realistic speed, the terrain and growth, and your hourly rate, then press Calculate and read total hours, job price and bush hogging cost per acre. The calculator page is the cost calculator, and it is the tool every figure in this post comes from. Enter your own rate, because the $85 rate used here is an example rate only, explicitly not a market rate.
Frequently Asked Questions
Q: What is rotary cutter cost per acre?
A: Rotary cutter cost per acre is the hourly rate divided by acres per hour, where acres per hour equals cutter width in feet times speed in miles per hour times efficiency divided by 8.25.
Q: Why does a 15 ft cutter cost less than half a 5 ft cutter per acre?
A: Width moves acres per hour in direct proportion. A 15 ft cutter is three times as wide as a 5 ft cutter, so it cuts three times as many acres per hour. At the page example rate on average ground, it costs $16 per acre against $47, both as example figures at the page example rate.
Q: What happens to rotary cutter cost per acre if I halve my speed?
A: Halving speed halves acres per hour and doubles the per acre price at the same hourly rate. A 6 ft cutter in average pasture goes from about 28 minutes per acre at 4 mph to about 55 minutes per acre at 2 mph, and its price at the page example rate goes from about $39 to about $78 per acre, both as example figures at the page example rate.
Q: Can a wide cutter on rough ground really cost less per acre than a narrow cutter on open ground?
A: Yes. A 15 ft cutter on rough ground costs $18 per acre at the page example rate, while a 5 ft cutter on open ground costs $44 per acre at the page example rate. The threefold width advantage is larger than the efficiency drop from 80 percent to 65 percent.
Q: Does a higher speed always lower rotary cutter cost per acre?
A: A higher speed lowers the per acre price in the formula, but only if you can hold that speed while the cut stays clean and safe. Thick brush may need 2 mph or less.
Q: How do I work out rotary cutter cost per acre for my own cutter and rate?
A: Enter your acreage, cutter width and realistic speed, terrain and growth, and your own hourly rate in the Bush Hogging Cost Calculator, then read total hours, job price and bush hogging cost per acre. The $85 rate in this post is an example rate only.
Read the Price From the Levers That Moved It
Rotary cutter cost per acre moves with width and speed in direct proportion. A wider cutter spreads the hourly rate over more acres, a faster speed does the same, and a slower speed or rougher ground pulls the price back up. The 15 ft cutter at $16 per acre on average ground, the 6 ft cutter doubling from about $39 to about $78 when speed halves, and the 15 ft cutter on rough ground at $18 still beating the 5 ft cutter on open ground at $44, all as example figures at the page example rate, are three views of the same formula.
