Calculating Acres Per Hour for a Mower

by / Wednesday, 05 March 2014 / Published in Tractor Tools Direct

I get a lot of questions to the tune of “how many acres per hour will that cut?”  I get them from people cutting their lawns as well as people cutting hay.  The answer is both simple and complicated – it really depends on the situation.  But there is a simple formula you can use to estimate:

Mower width in inches times forward speed in miles per hour divided by 100.

Kubota L Series

This formula will give you the maximum mowing capacity, in acres per hour, assuming you are always cutting new material (no overlap).  Since we all know that never happens you really need to add an efficiency factor to this formula which will take into account overlap between passes as well as doubling back and other times when the mower is not actually cutting.  For example, if I were using a 60 inch mower, I might assume there is 6 inches of overlap between passes, or a 10 percent reduction.  In addition, I might estimate that I spend 10 percent of my time turning around, slowing and/or trimming around obstacles, or moving from one area to another.  So my actual efficiency is only around 80%.

Cutting width is obvious, but what about speed?  Most tractors and mowers do not have speedometers.  Here you may have to estimate, or time yourself for a given distance and do the math.  Some rules of thumb would be

3 mph – walking speed

4 mph – brisk walk

6 mph – a decent jog.  About the maximum speed a sickle bar mower can cut.  Also any tractor with small wheels, like a subcompact, will start to get pretty uncomfortable to ride on in a bumpy hay field if you go much faster than this.

8mph – about the maximum speed a finish mower can cut before cut quality begins to suffer (assuming adequate horsepower).

10 mph – easily achievable by a mid-sized utility tractor with a disc or drum mower, assuming it has the horsepower.

15 mph – Possible with a large tractor (category 2 or larger) and drum mower.  Probably too fast to be safe for anything smaller.  This is FLYING for a tractor in a field.

Power is usually the limiting factor as far as speed goes.  Most compact tractors and dedicated mowers find their sweet spot between 4 and 6 mph.

Back to our example, if I am able to cut at 6 mph, the calculation would look like this:

60 inches X 6 mph x 80% / 100 = 2.88 (round to 2.9) acres per hour.

I’ve found this formula to be very useful over the years.  I will sometimes use it to check my efficiency by timing myself in a field of known size.  Since I know my speed (my Carraro TTR4400 has a speedometer) I can back-calculate to get my mowing efficiency.  I find 80% to be pretty good.  It is possible to do better on a large, rectangular field, but is usually below that mark when mowing small irregular fields.

Try it yourself this spring, and let us know what you find.  Can you beat 80%?  Maybe you find you are able to mow faster than the guidelines above.  Send us your comments at info@tractortoolsdirect.com, and we’ll share them here in a later post.

2 Responses to “Calculating Acres Per Hour for a Mower”

  1. Countryguy says :

    Thanks for the article. I can offer that I am consistently able to run my Kubota L series w/ Galfre 130 upwards of 8-10 on the long straight runs. Actually I look at any field I cut with the intent of maximizing speed on the longest runs possible now. I save some parts as sections for ‘mop up’ afterwards. Sooner I can Tedder the bulk the better. As for the overlap factor, i would say it is also proportional to speed It is more difficult to ‘run the line’ looking backwards on your edge. Well for a rookie anyway! In short I have the numbers and this formula is a good one to use.

  2. Pat Goodwin says :

    Great info! Thanks for your post. Let us know what kind of numbers you get this spring…. If we EVER get to hay season!

    Pat

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