How to use bush hog acres per hour calculator? Enter cutter width in feet, average speed in miles per hour, and field efficiency as a percent, then read the acres per hour result. A 6 foot cutter at 4 miles per hour and 75 percent efficiency gives 2.18 acres per hour, so a 20 acre pasture takes about 9.2 hours.
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How to Use Bush Hog Acres Per Hour Calculator: The Formula
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 Acres Per Hour Calculator on the homepage uses the same formula.
To get time from a rate, divide acres by acres per hour. That gives hours. Multiply the part after the decimal point by 60 to turn it into minutes. For example, 9.17 hours is 9 hours plus 0.17 times 60 minutes, which is about 9 hours and 10 minutes. Keep the rate and the time together when you write the plan down, so you can see which inputs produced which time. Times in this guide use the unrounded rate, and only the final value is rounded.
Step 1 Enter the Working Width
Enter the working width, not the width printed on the side of the cutter. Working width is the width of ground actually cut on each pass, after overlap is taken out. Overlap is the strip of ground cut twice where one pass meets the next, and it does not count as new ground. If the cutter is 6 foot wide and you overlap by about half a foot on each pass, the working width is about 5.5 foot, and that is the number to enter.
Measure the working width in the field if you can. Cut one straight pass, measure the width of fresh cut ground from the edge of the last pass to the edge of the new pass, and use that measurement. If you cannot measure it, use a small overlap allowance and be honest about it in your plan. Using the full machine width when the real working width is smaller makes the rate too high and the time too short.
Step 2 Enter the Average Speed
Enter the average speed you can hold while the blades are cutting cleanly, not the top speed of the tractor and not the speed on a short open run. Average speed is lower than top speed, because it includes slower ground, turns, rough patches, and places where thick growth forces you to slow down. If you enter top speed, the calculator will give a rate you cannot hold for an hour.
Thick tall woody growth needs slower speeds. That is a verified fact on the bush hog calculator page, and it matters most on the first cut of overgrown land. Rocks, stumps, and ditches force detours and lower efficiency, so walk the field first and mark what you find. Slopes call for slower safer passes, so do not plan a slope at the same speed as flat open ground.
Step 3 Enter Field Efficiency
Efficiency is the share of the hour spent covering new ground. The rest of the hour goes to turning, overlapping, slowing, and stopping. Efficiency is the input most people guess, and it is the input that most often explains why a real job takes longer than the plan. Use the bands published on this site as a starting point, and move down when the field is awkward.
| Field type | Efficiency |
|---|---|
| Small or irregular fields | 55 to 65 percent |
| Average fields | 70 to 75 percent |
| Large rectangular fields | 80 to 85 percent |
| Ideal fields with GPS guidance | 85 to 90 percent |
Use 75 percent as a planning start for average pasture. That is the middle of the average band, and it is the efficiency used in the two worked examples in this guide. Use 65 percent for a small or irregular field, for thick growth, or for a field with many obstacles. Use 85 percent only for a large rectangular field with long straight passes and little stopping. The ideal band is 85 to 90 percent, not higher, and it applies only to ideal fields with GPS guidance.
Worked Example 1 A 6 Foot Cutter at 4 Miles Per Hour
This is the worked example on the bush hog calculator page. Take a 6 foot cutter at 4 miles per hour in average pasture at 75 percent efficiency. Work it out step by step so you can check the calculator result by hand.
First multiply width by speed. 6 times 4 equals 24. Then multiply by efficiency as a decimal. 24 times 0.75 equals 18. Then divide by 8.25. 18 divided by 8.25 equals 2.18 acres per hour after rounding. The full result before rounding is 2.1818 acres per hour.
Now turn that rate into time for a 20 acre pasture. Divide acres by the rate. 20 divided by 2.18 equals 9.17 hours, so about 9.2 hours. That is cutting time only. It does not include travel to the field, fuel stops, or time spent clearing debris. In hours and minutes, 0.17 times 60 equals about 10 minutes, so the cutting time is about 9 hours and 10 minutes.
Use the same steps for a smaller field. A 10 acre field at 2.18 acres per hour takes 10 divided by 2.18, which equals 4.58 hours, or about 4 hours and 35 minutes. A 5 acre field takes 5 divided by 2.18, which equals 2.29 hours, or about 2 hours and 17 minutes. The method is the same every time: rate first, then acres divided by rate.
Worked Example 2 A 6 Foot Cutter at 4.5 Miles Per Hour
This is the homepage example, and it uses a faster speed than the first example, so keep the two examples separate. Take a 6 foot cutter at 4.5 miles per hour and 75 percent efficiency. The speed is higher, so the rate is higher and the time is shorter, even though the cutter and the efficiency are the same.
First multiply width by speed. 6 times 4.5 equals 27. Then multiply by efficiency as a decimal. 27 times 0.75 equals 20.25. Then divide by 8.25. 20.25 divided by 8.25 equals 2.45 acres per hour after rounding. The full result before rounding is 2.4545 acres per hour.
Now turn that rate into time for a 20 acre pasture. 20 divided by 2.45 equals 8.15 hours, so about 8.2 hours. That is cutting time only, just as in the first example. The difference between the two examples is 9.17 hours minus 8.15 hours, which equals 1.02 hours, so about 1 hour saved on 20 acres by raising the speed from 4 miles per hour to 4.5 miles per hour while holding efficiency at 75 percent.
That saving is real only if 4.5 miles per hour is a cutting speed you can hold on that ground. If thick growth or rough ground forces you back to 4 miles per hour, the time goes back to about 9.2 hours. Do not plan on the faster time unless you have held the faster speed before on similar ground. Label each plan with its speed, so you know which example you used.
Rate Table at 4 Miles Per Hour
The table below is the typical rotary cutter rates table from the bush hog calculator page, all at 4 miles per hour. Read across a row for your cutter width, then down a column for your efficiency. Every cell was recalculated from the formula in this task.
| Cutter width | Rate at 75 percent efficiency | Rate at 65 percent efficiency |
|---|---|---|
| 4 foot | 1.45 acres per hour | 1.26 acres per hour |
| 5 foot | 1.82 acres per hour | 1.58 acres per hour |
| 6 foot | 2.18 acres per hour | 1.89 acres per hour |
| 7 foot | 2.55 acres per hour | 2.21 acres per hour |
| 10 foot | 3.64 acres per hour | 3.15 acres per hour |
| 15 foot | 5.45 acres per hour | 4.73 acres per hour |
Check one row by hand. For a 10 foot cutter at 4 miles per hour and 75 percent efficiency, 10 times 4 equals 40, 40 times 0.75 equals 30, and 30 divided by 8.25 equals 3.64 acres per hour after rounding. For the same cutter at 65 percent efficiency, 10 times 4 times 0.65 equals 26, and 26 divided by 8.25 equals 3.15 acres per hour after rounding.
Common Mistakes When Using the Calculator
First, entering machine width instead of working width. Measure the fresh cut strip and use that figure. Second, entering top speed instead of average cutting speed. Use the speed you can hold while cutting cleanly, including slower ground and turns. Third, using 100 percent efficiency. No real field works at 100 percent, because turning and overlap always take time. Fourth, using one rate for every part of a field. Split the field into parts that match the ground, work out the time for each part, and add the times together.
Frequently Asked Questions
Q: How to use bush hog acres per hour calculator?
A: Enter cutter width in feet, average speed in miles per hour, and field efficiency as a percent, then read the acres per hour result. A 6 foot cutter at 4 miles per hour and 75 percent efficiency gives 2.18 acres per hour.
Q: What formula does the bush hog acres per hour calculator use?
A: Acres per hour equals width in feet times speed in miles per hour times efficiency, divided by 8.25. Efficiency is a decimal in the formula, so 75 percent is 0.75.
Q: How long does it take to bush hog 20 acres with a 6 foot cutter?
A: At 4 miles per hour and 75 percent efficiency, the rate is 2.18 acres per hour, so 20 acres takes about 9.2 hours of cutting time. At 4.5 miles per hour it takes about 8.2 hours.
Q: What efficiency should I enter in the bush hog calculator?
A: Start at 75 percent for average pasture. Drop to 65 percent for a small or irregular field, for thick growth, or for many obstacles. Reserve 85 percent for a large rectangular field with long straight runs.
Q: Why is my real bush hog rate lower than the calculator result?
A: The most likely causes are a lower working speed, a lower efficiency, or a smaller working width than the machine width. Check the speed you actually held and the fresh cut width.
Q: Can I use the bush hog calculator for a different cutter width?
A: Yes. Enter your own working width in feet and your own speed and efficiency. At 4 miles per hour and 75 percent efficiency, a 4 foot cutter gives 1.45 acres per hour and a 10 foot cutter gives 3.64.
Plan From the Rate, Not From a Guess
A bush hog rate is a result from width, speed, and efficiency, not a single number you can copy from another site. That is how to use bush hog acres per hour calculator: enter your working width, enter a speed you can hold while cutting, choose an efficiency that matches the field, and check the result by hand. Then divide the field size by the rate to get cutting time, and add travel and stops on top. Run your own numbers through the Bush Hog Acres Per Hour Calculator before the next job, and keep a record of the time each field takes so your next estimate is based on real work. Read the guide on how to calculate acres per hour for the full method. For cost planning, use the live bush hogging cost calculator.
