How fast to bush hog thick brush safely? Slow down to a speed you can hold while the blades keep cutting cleanly in one pass. A 6 foot cutter at 3 miles per hour and 75 percent efficiency cuts 1.64 acres per hour, and at 2 miles per hour it cuts 1.09 acres per hour.
Table of Contents
Why Thick Brush Needs a Slower Speed
Thick tall woody growth needs slower speeds. That is a verified fact on the bush hog calculator page, and it is the first rule for thick brush. The blades have more material to chop on each pass, so the cutter needs more time on each stem. If you drive too fast, the blades leave uncut stems, the cut looks ragged, and you may need a second pass. A second pass doubles the time for that ground, so a slow first pass that cuts cleanly can be faster overall than a fast first pass that needs to be repeated.
Thick brush also hides hazards. Rocks, stumps, and ditches force detours and lower efficiency, so walk the field first and mark what you find. A rock hidden in tall growth can damage the cutter and throw debris, and a stump can stop a pass in its tracks. Slopes call for slower safer passes, so do not plan a slope at the same speed as flat open ground. The slower speed gives you time to see the ground, steer round a hazard, and stop safely.
The Formula at Low Speeds
Acres per hour equals width in feet times speed in miles per hour times efficiency, divided by 8.25. Efficiency is written as a decimal in the formula, so 75 percent is 0.75 and 65 percent is 0.65. The constant 8.25 comes from 43560 divided by 5280. That is the number of square feet in an acre divided by the number of feet in a mile.
The guide on how to calculate acres per hour gives the same formula in full, and the Acres Per Hour Calculator on the homepage uses the same formula. The Bush Hog Acres Per Hour Calculator uses the same formula with cutter width as the width input.
To get time per acre from a rate, divide 60 by acres per hour. That gives minutes per acre. For example, a rate of 1.64 acres per hour gives 60 divided by 1.64, which equals 36.7 minutes per acre. To get total time, divide acres by acres per hour. That gives hours. Keep the rate, the minutes per acre, and the total time together when you write the plan down. Times in this guide use the unrounded rate, and only the final value is rounded.
How Fast to Bush Hog Thick Brush: Rates for a 6 Foot Cutter
The table below gives rates for a 6 foot cutter at low speeds, at 65 percent efficiency and at 75 percent efficiency. Use 65 percent efficiency for thick brush as a planning start, because detours and stops are common in thick growth. Every cell was recalculated from the formula in this task.
| Speed in miles per hour | Rate at 65 percent efficiency | Rate at 75 percent efficiency | Minutes per acre at 75 percent efficiency |
|---|---|---|---|
| 2 | 0.95 acres per hour | 1.09 acres per hour | 55.0 |
| 2.5 | 1.18 acres per hour | 1.36 acres per hour | 44.0 |
| 3 | 1.42 acres per hour | 1.64 acres per hour | 36.7 |
| 3.5 | 1.65 acres per hour | 1.91 acres per hour | 31.4 |
| 4 | 1.89 acres per hour | 2.18 acres per hour | 27.5 |
Check one cell by hand. At 2.5 miles per hour and 65 percent efficiency, 6 times 2.5 equals 15, 15 times 0.65 equals 9.75, and 9.75 divided by 8.25 equals 1.18 acres per hour after rounding. At 3 miles per hour and 75 percent efficiency, 6 times 3 equals 18, 18 times 0.75 equals 13.5, and 13.5 divided by 8.25 equals 1.64 acres per hour after rounding.
Read the minutes per acre column when you plan a day. At 2 miles per hour and 75 percent efficiency, each acre takes 55.0 minutes, so 5 acres takes about 4 hours and 35 minutes of cutting time. At 3 miles per hour and 75 percent efficiency, each acre takes 36.7 minutes, so 5 acres takes about 3 hours and 3 minutes. At 4 miles per hour and 75 percent efficiency, each acre takes 27.5 minutes, so 5 acres takes about 2 hours and 17 minutes. The faster speed saves time only if it cuts cleanly in one pass.
Rates for a 10 Foot Cutter in Thick Brush
The table below gives rates for a 10 foot cutter at the same low speeds, at 65 percent efficiency and at 75 percent efficiency. A wider cutter covers more ground at the same speed, but it also has more width to drive through thick growth, so do not assume it can hold the same speed as a 6 foot cutter on the same ground. Every cell was recalculated from the formula in this task.
| Speed in miles per hour | Rate at 65 percent efficiency | Rate at 75 percent efficiency | Minutes per acre at 75 percent efficiency |
|---|---|---|---|
| 2 | 1.58 acres per hour | 1.82 acres per hour | 33.0 |
| 2.5 | 1.97 acres per hour | 2.27 acres per hour | 26.4 |
| 3 | 2.36 acres per hour | 2.73 acres per hour | 22.0 |
| 3.5 | 2.76 acres per hour | 3.18 acres per hour | 18.9 |
| 4 | 3.15 acres per hour | 3.64 acres per hour | 16.5 |
Check one cell by hand. At 2.5 miles per hour and 65 percent efficiency, 10 times 2.5 equals 25, 25 times 0.65 equals 16.25, and 16.25 divided by 8.25 equals 1.97 acres per hour after rounding. At 3.5 miles per hour and 75 percent efficiency, 10 times 3.5 equals 35, 35 times 0.75 equals 26.25, and 26.25 divided by 8.25 equals 3.18 acres per hour after rounding.
How to Test a Speed on a Short First Pass
Do not choose a speed from a table and hold it for the whole field. Test it on a short first pass, then adjust. Start at a slow speed, cut a short straight pass through the thickest growth you can see, stop, and look at the cut. If the cut is clean and the blades kept their speed, you can try a slightly faster speed on the next pass. If the cut leaves uncut stems, if the blades slow down, or if the tractor struggles, stay at the slow speed or slow down further.
Walk the field first, before the test pass. Mark stumps, rocks, holes, and wire hidden in tall grass, and check that the cutter can pass through gates and turn inside the field. Plan long straight passes with a small overlap, and plan the turning room at the ends of the field. If the field is steep, plan slower safer passes on the slope, and do not try to hold the same speed as on flat ground. If the ground is wet, wait for firmer ground if you can, because wet ground forces slower speed and can rut easily.
Signs You Are Going Too Fast in Thick Brush
The first sign is the cut itself. Uncut stems, torn stems, and patches of standing growth after a pass mean the blades did not have time to chop the material. The second sign is the sound and feel of the tractor and cutter. If the blades slow down, if the tractor labours, or if the cutter bounces over hidden ground, the speed is too high for that growth. Slow down until the blades hold their speed and the cut is clean.
The third sign is debris. Thick brush throws debris, so keep people and animals well clear, and never let anyone walk beside the cutter while it is running. If debris is flying further than you expected, or if you hit a rock or stump you did not see, stop, inspect the cutter, and walk that ground before you go on. The fourth sign is the plan itself. If you are falling behind the time you planned from a slow rate, do not speed up to catch up. Recalculate the time from the speed you can actually hold, and split the field across two days if you need to.
Planning Time at a Slow Speed
Plan the time from the slow rate, not from the average pasture rate. At 3 miles per hour and 65 percent efficiency, a 6 foot cutter gives 1.42 acres per hour, so 10 acres takes 10 divided by 1.42, which equals 7.05 hours, or about 7 hours and 3 minutes. At the same speed and efficiency, a 10 foot cutter gives 2.36 acres per hour, so 10 acres takes 10 divided by 2.36, which equals 4.23 hours, or about 4 hours and 14 minutes. Those are cutting times only. They do not include travel, fuel stops, or time spent walking the field. Read the guide on understanding field efficiency for how second passes and stops lower efficiency.
Frequently Asked Questions
Q: How fast to bush hog thick brush safely?
A: Slow down to a speed you can hold while the blades keep cutting cleanly in one pass. A 6 foot cutter at 3 miles per hour and 75 percent efficiency cuts 1.64 acres per hour, and at 2 miles per hour it cuts 1.09 acres per hour.
Q: Is 3 miles per hour a good speed for thick brush?
A: It is a useful planning speed for thick brush with a 6 foot cutter, giving 1.64 acres per hour at 75 percent efficiency and 1.42 at 65 percent efficiency. Test it on a short first pass, and slow down if the cut leaves uncut stems.
Q: How many acres per hour can a 6 foot bush hog cut in thick brush?
A: At 3 miles per hour and 75 percent efficiency, a 6 foot cutter gives 1.64 acres per hour. At 2 miles per hour and 65 percent efficiency, it gives 0.95 acres per hour.
Q: How many acres per hour can a 10 foot bush hog cut in thick brush?
A: At 3 miles per hour and 75 percent efficiency, a 10 foot cutter gives 2.73 acres per hour. At 2 miles per hour and 65 percent efficiency, it gives 1.58 acres per hour.
Q: Why does thick brush take longer than open pasture?
A: Thick tall woody growth needs slower speeds, and rocks, stumps, and ditches force detours and lower efficiency. A second pass, if the first pass leaves uncut stems, doubles the time for that ground.
Q: Should I do a second pass if the first pass leaves uncut stems?
A: A second pass will clean up the ground, but it doubles the time for that ground. It is usually faster to slow down on fresh ground so the first pass cuts cleanly, and to count any second pass time in your plan.
Choose the Speed From the Field
There is no single safe speed for thick brush, because thick brush is not one condition. Walk the field, mark the hazards, start slow, test a short first pass, and hold the speed that cuts cleanly in one pass. Use the low speed tables in this guide to turn that speed into a rate and a time, and run your own numbers through the Bush Hog Acres Per Hour Calculator before the next job. A slow clean pass is faster than a fast ragged pass that needs to be repeated, and it is safer. That is how fast to bush hog thick brush safely on your own ground. For cost planning, use the live bush hogging cost calculator. The bush hog rotary cutter productivity guide gives the general productivity view.
