Mowing Cost Calculator

Background.

Mowing cost is really two questions wearing one coat. The first is how long the lawn takes, which is machinery arithmetic. The second is what that time is worth, which is a judgement only you can make — and it is the judgement that decides whether hiring a service is extravagant or obvious.

The time half has a published answer. Agricultural engineering extension has been printing the same field-capacity equation for decades: acres per hour equals the cutting width in feet, times the ground speed in miles per hour, times the field efficiency, divided by 8.25. Iowa State Extension's PM 696 gives it as equation (4) and derives the constant in a footnote — 43,560 square feet in an acre divided by 5,280 feet in a mile is exactly 8.25, so it is a unit conversion rather than a fudge factor. The University of Wisconsin's A3510 prints the identical formula with a worked example that this calculator reproduces exactly: a 9-foot machine at 5 miles per hour and 75% efficiency covers 4.09 acres an hour.

Field efficiency is where honesty is required. It is the fraction of the theoretical rate you actually achieve once you account for turning at the ends, overlapping your passes, stopping to empty the bag and walking round the trampoline. Wisconsin's table gives 55 to 85 per cent for a pull-type mower conditioner. But that is a machine in an open hay field, and no source consulted for this page publishes a field efficiency for a suburban lawn with three trees, two beds, a fence line and a swing set in it. So this calculator refuses to assume one. Its default basis is measured: you time a single cut, and it works backwards to tell you the efficiency you are really getting. On the worked example that comes out at 59 per cent — plausible, but a number you would never have guessed and could not have looked up.

The cost half is deliberately plain. Fuel is running hours times gallons per hour times the pump price. Blades, oil, filters and the mower itself are folded into one running cost per hour, because that is how you can actually estimate them: divide what you spend on the machine in a year by the hours you run it. Then your own time is added at whatever rate you choose, and the default is zero — so the first number you see is pure out-of-pocket cost, which is usually startlingly small.

That is the point at which the comparison gets interesting. An 8,000 square foot lawn costs under two dollars a cut in fuel and wear, so a fifty-dollar service looks absurd. But the same lawn takes 35 minutes, which over 26 cuts is more than fifteen hours, and the service is charging about 86 dollars per hour of mowing. Value your own hour anywhere near that and the arithmetic flips. Nothing on this page tells you which answer is right; it just makes both visible at once.

One thing this page will not do is quote you a price. Fuel, wages and lawn-service rates are regional, seasonal and change constantly, and a calculator that shipped its own figures for them would be confidently wrong within a month. Every price here is a placeholder for your number.

What is mowing cost calculator?

Effective field capacity is the rate at which a machine actually covers ground — acres per hour, measured over real working time including turns and stops. Theoretical field capacity is the same figure with all those losses removed: full width, constant speed, no interruptions. Field efficiency is simply the ratio of the two, expressed as a percentage.

The three are linked by one equation. Theoretical capacity is the cutting width in feet times the speed in miles per hour divided by 8.25. Effective capacity is that multiplied by the field efficiency. Rearranged, field efficiency is effective capacity divided by theoretical capacity times a hundred, which is exactly how this page works backwards from a cut you have timed.

Field efficiency already includes overlap. Iowa State's PM 696 lists failure to use the full operating width among the losses it covers, alongside turning, idle travel, emptying and operator rest. That is why this calculator has no separate overlap control: adding one beside a field-efficiency control would count the same loss twice and quietly inflate every time on the page.

Cutting width is the nominal width of the deck, not the machine's overall width. A 21-inch push mower cuts 1.75 feet per pass; a 42-inch rider cuts 3.5 feet, so at the same speed and efficiency it finishes in half the time.

What the calculator does not know: whether your lawn needs trimming and edging afterwards, how long the string trimmer takes, what disposal of clippings costs, whether the service also fertilises, or how a battery mower's charging cost compares. Battery owners should enter zero gallons per hour and fold the electricity into the running cost per hour.

How to use this calculator.

1. 01Measure the grass you actually mow, in square feet, and subtract the house, drive, patio and beds. If you know the lot in acres, multiply by 43,560.
2. 02Enter the cutting width of your deck in inches — the nominal cut, not the machine's overall width — and your ground speed in miles per hour. To measure speed instead of guessing it, mark 88 feet, time yourself walking or driving it, and divide 60 by the seconds taken.
3. 03Leave the time basis on measured and time one real cut with a phone stopwatch. That is the only way to get a field efficiency that means anything for your lawn, and the calculator reports it back to you.
4. 04Switch to the computed basis only when you are comparing hypothetical machines — a 21-inch push against a 42-inch rider, say — where the efficiency assumption cancels out of the comparison.
5. 05Fill in fuel burn, fuel price and running cost with your own numbers. Measure fuel burn by filling the tank, mowing for a timed hour, and refilling. For a battery mower enter zero gallons per hour and put the charging cost into the running cost.
6. 06Leave your time at zero first, to see the out-of-pocket cost. Then set it to what you would actually pay to get that hour back and read the verdict again.
7. 07Enter a real quote from a local service, not an average. Compare the service rate per mowing hour against your own hourly value — that single pair of numbers is the whole decision.

The formula.

The time model comes first. The deck width converts from inches to feet by dividing by 12, so a 21-inch mower cuts 1.75 feet. Theoretical capacity is then width times speed divided by 8.25: 1.75 times 2.5 divided by 8.25 gives 0.530 303 030 3 acres per hour. That 8.25 is not a lookup value. It is 43,560 square feet per acre divided by 5,280 feet per mile, which is the exact factor that converts feet times miles per hour into acres per hour, and this calculator computes it from the two NIST unit definitions rather than typing it in. You can check it the long way: 1.75 feet times 2.5 miles per hour times 5,280 feet per mile is 23,100 square feet an hour, and dividing by 43,560 gives the same 0.530 303 030 3.

On the measured basis you supply the time and the calculator works backwards. An 8,000 square foot lawn is 8,000 divided by 43,560, or 0.183 654 729 1 acres. Timed at 35 minutes, that is 0.583 333 hours, so the effective capacity is 0.183 654 729 1 divided by 0.583 333, which is 0.314 836 678 5 acres per hour. Field efficiency is that over the theoretical figure: 0.314 836 678 5 divided by 0.530 303 030 3 times 100 equals 59.369 202 226 3 per cent. On the computed basis the same equation runs the other way — effective capacity is theoretical times your efficiency, and the time is the acreage divided by it.

Costs are then straightforward, and everything scales with running hours. Fuel is 0.583 333 hours times 0.3 gallons per hour times 3.50 dollars, which is 0.612 5. Blades, oil and machine wear at 2.00 per hour add 1.166 666 7. Your own time at zero adds nothing. The three together make 1.779 166 666 7 per cut. Over 26 cuts that is 46.258 333 333 3, against 1,300 for a service at 50 a visit — a difference of 1,253.741 666 666 7 in favour of doing it yourself.

The number that reframes the comparison is the service rate per mowing hour: 50 divided by 0.583 333 hours is 85.714 285 714 3. That is what the service charges for each hour of mowing it does. Set your own hourly value above that and the verdict flips, which is exactly what the calculator does — the verdict is classified on the unrounded season difference, with the band edge at exactly zero, so a difference of four cents is still reported as a difference and not rounded into a tie.

There is no intermediate rounding anywhere in this calculation. Every quantity is carried at forty significant digits and rounded once, at the end, to ten decimal places. Nothing is quantised — not even the number of cuts, because mowing every ten days through a season is a perfectly reasonable 22.5 cuts and there is no reason to force it to a whole number.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Iowa State University Extension, PM 696, "Machinery Management: Estimating Field Capacity of Farm Machines", revised April 2001, prepared by Mark Hanna (originally George Ayres and David Williams). Source of equation (1) theoretical field capacity = width (ft) x speed (mph) / 8.25, equation (3) field efficiency = EFC/TFC x 100, equation (4) effective field capacity, footnote 1 deriving the 8.25 constant from 43,560 / 5,280, and the mower rows of the Iowa farm machinery table. Retrieved 2026-07-31; open access PDF, read in full.
2. [2]Schuler, R.T. and Frank, G.G. A3510, "Estimating Agricultural Field Machinery Costs", University of Wisconsin-Extension, Cooperative Extension, March 1991. Independent statement of the same equation — "multiply forward speed in miles per hour by the machine width in feet and by the field efficiency, and then divide by 8.25" — plus the Worksheet 1 worked example 5 x 9 x 0.75 / 8.25 = 4.09 ac/hr and Table 5, which gives 0.55-0.85 field efficiency for a pull-type mower conditioner. Used as the independent check on Iowa State. Retrieved 2026-07-31; open access PDF, read in full.
3. [3]National Institute of Standards and Technology, Handbook 133 – 2026, Appendix E, "General Tables of Units of Measurement". Units of Area: 1 acre = 43,560 square feet. Units of Length: 1 mile = 5,280 feet. Together these make the 8.25 field-capacity constant an exact unit conversion rather than an empirical factor. Retrieved 2026-07-31; open access PDF.