Electric Lawn Mower Battery Runtime Calculator

Planning Your Mowing Sessions

Battery-powered lawn mowers have exploded in popularity as homeowners look for quieter, cleaner alternatives to gasoline models. Yet prospective buyers often struggle to determine whether a given battery will last long enough to mow their entire yard. Manufacturers advertise capacity in watt-hours and sometimes estimate runtime, but those numbers rarely account for mowing speed, deck width, or real-world power draw. This calculator brings those factors together to estimate how much grass you can cut on a single charge and how many battery swaps you might need.

The key to understanding battery runtime is recognizing that energy stored in the battery, measured in watt-hours, is expended by the mower at a rate determined by its power draw. Dividing capacity by power yields runtime in hours. Converting hours to minutes provides a more intuitive figure. To translate runtime into area covered, we also consider the width of the mower's cutting deck and your walking speed. Multiplying speed by deck width (converted to feet) gives the strip of grass cleared per minute, and multiplying that by runtime yields total area.

The equation for runtime appears in MathML as $t=C/P$, where C is battery capacity in watt-hours and P is power draw in watts. Coverage area $A=tvw$ follows from multiplying runtime t by walking speed v in feet per minute and deck width w in feet. These formulas assume level ground and steady power consumption.

Consider a mower with a 400 Wh battery and a 600 W motor. The runtime calculation yields 0.67 hours, or about 40 minutes. With a 20-inch deck (1.67 feet) and a comfortable walking speed of 3 mph (264 feet per minute), the mower can cover roughly 17,600 square feet per charge. If your yard is 5,000 square feet, one charge is ample. The calculator also reports how many full charges are required for the specified yard size, rounding up to the nearest whole number to account for partial passes.

The scenario table below automatically generates runtime and coverage estimates for three battery capacities: half, equal, and one-and-a-half times the capacity you entered. This illustrates the benefit of carrying a spare battery or upgrading to a higher-capacity pack. For example, doubling capacity roughly doubles runtime and area, though actual performance depends on conditions such as grass height and moisture.

Unlike gasoline mowers, which can be refueled quickly, battery mowers require charging time between sessions. Knowing how much area you can cover per charge helps you decide whether additional batteries or a model with a larger pack is necessary. It also informs strategies like mowing in sections over multiple days, which may be practical for large properties.

Several factors can reduce runtime below the theoretical value calculated here. Thick or wet grass increases power draw as the motor works harder. Self-propelled features consume additional energy, as do accessories like headlights. Battery age and temperature also affect usable capacity. Nonetheless, the formulas provide a useful baseline, and you can adjust the power input upward to simulate tougher mowing conditions.

If you are comparing electric to gasoline mowers, our Electric vs Gas Lawn Mower Cost Calculator offers a broader cost analysis. To estimate how long mowing will take regardless of battery life, consult the Lawn Mowing Time Calculator.

From an environmental perspective, electric mowers produce no direct emissions and are quieter, benefiting both users and neighbors. The energy used can come from renewable sources if your utility offers them or if you have home solar panels. Understanding battery runtime ensures you can complete mowing without resorting to backup gasoline equipment, maximizing these benefits.

As a worked example, suppose your yard covers 8,000 square feet. Using the default values, runtime is 40 minutes, and area coverage is 17,600 square feet, meaning one charge suffices. If you had a smaller 200 Wh battery, runtime drops to 20 minutes, covering 8,800 square feet—still enough, but with little margin. Conversely, a 600 Wh battery extends runtime to an hour, covering more than 26,000 square feet.

Limitations of this calculator include the assumption of constant walking speed and power draw. Actual mowing often involves turns, obstacles, and varying grass density. The tool also does not account for battery management systems that may cut power before full discharge to protect the cells. Nevertheless, the estimates provide a solid starting point for planning.

Use the form above to experiment with different scenarios. Adjust power draw to simulate mulching vs. bagging, or tweak deck width when evaluating aftermarket blade kits. The transparency of the calculations helps you make informed decisions about equipment purchases and mowing strategies.