LawnBiz Tools

Mowing Time Calculator

How long a lawn takes, from deck width and ground speed. This is the input every pricing decision depends on.

Mowing time —

Enter your numbers below.

Your mower and the lawn

Pre-filled with the worked example below. Change every field to your own numbers.

Enter the number, then pick the unit below.
21 push, 36-48 walk-behind, 48-72 zero-turn.
3 walking, 5-8 riding. Cutting speed, not transport speed.
Allows for overlap, turns and obstacles. 80 open, 60 cluttered.

These are your numbers, not market rates. This calculator works from the costs you enter. It does not tell you what your area pays — that varies by region, season and year, and any site quoting you a single national figure is guessing. Use this to find the price that covers your costs and target profit, then sanity-check it against what you can actually win locally.

Where this formula comes from Show the arithmetic

The constant 99 is a unit conversion, not a fudge factor, and it is worth seeing where it comes from: 

1 mph                  = 5,280 ft travelled per hour
deck width W inches    = W / 12 feet
swept area per hour    = 5,280 x (W / 12)  = 440 x W sq ft
1 acre                 = 43,560 sq ft
                       ---------------------------------
acres per hour         = 440W / 43,560     = W / 99

  acres/hour = (mph x deck width in inches) / 99

Then apply efficiency for overlap, turns and obstacles:

  real acres/hour = (mph x W / 99) x efficiency

At 80% efficiency that is equivalent to dividing by 124,
which is the constant Exmark publish (99 / 0.8 = 123.75).

Worked example

8,000 sq ft lawn, 21in push mower at 3 mph, 80% efficiency

acres/hour  = (3 x 21) / 99 x 0.80
            = 0.63636 x 0.80
            = 0.50909 acres/hour

area        = 8,000 / 43,560 = 0.18365 acres

time        = 0.18365 / 0.50909
            = 0.3607 hours
            = 21.6 minutes

This is mowing time only. Trimming, edging and blowing are often a third or more of the time on a residential property, and on small lots can exceed the mowing itself. Add them before pricing, or small properties will be underpriced every time — then feed the total into the price calculator.

What equipment does to the economics

Running the same one-acre lawn through three machines at 80% efficiency shows why equipment choice dominates this business:

MowerSpeedAcres/hourTime for 1 acre
21" push3 mph0.511 hr 58 min
36" walk-behind4 mph1.1652 min
48" zero-turn6 mph2.3326 min
60" zero-turn7 mph3.3918 min

Computed with the formula above at 80% efficiency, not surveyed. A 60-inch zero-turn covers the same ground roughly 6.7x faster than a 21-inch push mower — which is the real argument for the equipment, and what the startup cost calculator weighs it against.

Common questions

How long does it take to mow an acre?

It depends entirely on deck width and ground speed, which is why a single answer would be useless. A 60-inch zero-turn at 5 mph covers about 2.42 acres per hour at realistic efficiency, so an acre takes roughly 25 minutes. A 21-inch push mower at 3 mph covers about 0.51 acres per hour, so the same acre takes nearly two hours.

That is nearly a five-to-one spread on identical ground, which is why equipment choice drives the economics of this business more than almost anything else.

Where does the number 99 in the formula come from?

It is a unit conversion, not a fudge factor. One mph is 5,280 feet per hour. A deck W inches wide is W/12 feet. So the swept area is 5,280 x W/12 = 440W square feet per hour, and dividing by 43,560 square feet per acre gives W/99 acres per hour per mph.

So acres/hour = (mph x deck width in inches) / 99. Exmark publish the same constant.

What efficiency should I use?

Around 80% for open lawns, and lower for anything with obstacles. Efficiency accounts for the ground you cover without cutting new grass: overlapping each pass, turning at the ends, and manoeuvring around trees, beds and play equipment.

Exmark treat 80% as representative of real conditions, which is where the /124 constant in their charts comes from — 99 divided by 0.8 is 123.75. A tight residential lawn with many obstacles can fall to 60% or below.

Does this include trimming and blowing?

No. This is mowing time only — the time the deck is actually cutting.

Trimming, edging and blowing are frequently a third or more of total time on a residential property, and on small lots they can exceed the mowing time. Add them separately before pricing the job, or you will underprice small properties systematically.

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