Cordless mower and removable battery on a partially mowed lawn

How to Estimate Mower Runtime From Battery Specs

ByKen

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If you want to know how to estimate mower runtime from battery specs, start with the run time the maker states for one named mower and one pack. Then scale that figure by the stored energy of the pack you plan to use. Makers state run time for a specific mower and pack, so any figure for a different pack is your own calculation, not a manufacturer claim. The method below uses only figures that EGO and Ryobi print, and it marks each assumption. Real run time changes with grass, cutting height and terrain.

Quick answer

  • Start with the run time the maker states for the same mower and pack. EGO’s 21-inch push mower is stated at up to 45 minutes with its 5.0Ah pack.
  • Convert each pack to watt-hours. EGO’s chart gives 280 Wh for 5.0Ah and 336 Wh for 6.0Ah.
  • Estimated run time = stated run time x (new Wh / stated Wh). For the 6.0Ah pack, 45 x 336 / 280 = 54 minutes. This is an estimate, not a manufacturer figure.
  • The sources we opened do not say that run time scales with watt-hours, so treat the result as a rough guide.

Safety notes before you charge or handle a pack

This method does not involve blade or deck work, but the pack still needs careful handling. Follow the maker’s charging and storage instructions. The sources we opened agree on these points.

  • Store and charge in a cool, dry place. DeWalt says: “Store and charge batteries in a cool, dry location.” EPA says: “It is best to store Li-ion batteries at room temperature.”
  • Do not use a damaged pack. DeWalt says: “Do not use batteries with visible damage or cracks.” EPA says: “The swelling indicates damage to the battery and is a potential fire hazard.”
  • Storage guidance from workplace safety. OSHA’s workplace guidance lists “Storing batteries in cool, dry locations.”

Do not open a pack or attempt a repair. A swollen, cracked or wet pack should be taken out of use, and the maker should be contacted.

What a stated run time means

EGO’s 21-inch push mower page says “Up to 45 minutes of run time on single charge with the recommended 56V 5.0 Ah ARC Lithium™ battery.” The phrase “up to” marks a maximum figure for that mower and that pack. It is a manufacturer claim, and the page does not say what grass, cutting height or slope the figure assumes.

EGO’s self-propelled 21-inch mower carries the same kind of claim: up to 60 minutes on a single charge with the recommended 56V 7.5Ah pack. Each figure belongs to its own mower, so do not carry one mower’s number over to another.

Husqvarna’s runtime chart frames the question in similar terms. It asks how much power you will have “when working on various tasks,” and it answers with a chart rather than one figure. That is a reminder that run time depends on the work as well as the battery. The sources we opened do not give separate figures for grass height, slope or terrain for any mower.

The stated figures

The table lists the run time and battery figures stated for four mowers or kits. Wh figures come from EGO’s battery chart, and the Ryobi listing states no Wh figure.

Mower or kit Pack stated Run time stated Wh stated Source
EGO 21-inch push mower 5.0Ah, included up to 45 minutes 280 Wh (chart) EGO 21-inch mower page; EGO battery chart
EGO 21-inch self-propelled mower 7.5Ah, included up to 60 minutes 420 Wh (chart) EGO self-propelled mower page; EGO battery chart
EGO 21-inch Select Cut self-propelled kit 7.5Ah, recommended up to 60 minutes 420 Wh (chart) EGO Select Cut kit page
Ryobi 40V 21-inch self-propelled kit two 40V 6Ah batteries up to 80 minutes not stated Ryobi kit page

The Select Cut listing also names a kit with two 6Ah batteries. The run time line on that listing is for the 7.5Ah pack, so no runtime is stated for the two-6Ah kit.

Before you start

  • Name the mower and the pack. A stated run time is tied to both. The EGO push mower figure is for its 5.0Ah pack, and the self-propelled figure is for its 7.5Ah pack.
  • Keep the word “up to” in your notes. A stated run time is a maximum for that setup, not a minimum you can count on.
  • Use the same kind of figure on both sides. Compare a stated Wh with a stated Wh, or a volts-times-Ah result with another volts-times-Ah result, and do not mix the two.

How to estimate runtime for another pack

  1. Write down the stated run time and its pack. For the EGO push mower, the stated figure is up to 45 minutes with the 5.0Ah pack. Record that the figure is a maximum.
  2. Find the Wh figure for the stated pack. EGO’s chart gives 280 Wh for the 5.0Ah pack. If a pack has no printed Wh figure, multiply its voltage by its Ah rating and label the result as your calculation.
  3. Find the Wh figure for the pack you plan to use. EGO’s chart gives 336 Wh for the 6.0Ah pack.
  4. Divide the new Wh by the stated Wh. 336 / 280 = 1.2.
  5. Multiply the stated run time by that ratio. 45 x 1.2 = 54 minutes. Write it as an estimate for that mower and pack.
  6. Adjust your expectations for conditions. Taller or wetter grass, self-propelled use and a partly charged pack can all shorten the time you get. The listings do not give a figure for any of these, so the adjustment is a judgment, not a number from a source.

Worked calculation for the push mower

The formula is: estimated run time = stated run time x (Wh of the pack you plan to use / Wh of the stated pack). The inputs are 45 minutes (stated), 280 Wh (stated pack) and the Wh of each pack you want to estimate. The table below uses the EGO chart for each Wh figure.

Pack for the push mower Wh (EGO chart) Calculation Estimated run time Status
5.0Ah (stated) 280 Wh 45 x 280 / 280 45 minutes Manufacturer claim, up to
6.0Ah 336 Wh 45 x 336 / 280 54 minutes Estimate, not stated by EGO for this mower
7.5Ah 420 Wh 45 x 420 / 280 67.5 minutes Estimate, not stated by EGO for this mower

The estimate rests on one assumption: run time moves in step with stored energy. The sources we opened do not state that rule for any mower.

Same method, self-propelled mower

Run the same steps on EGO’s self-propelled 21-inch mower. Its stated figure is up to 60 minutes with the recommended 7.5Ah pack, which is 420 Wh on the chart. A 6.0Ah pack at 336 Wh gives 60 x 336 / 420 = 48 minutes. That is an estimate for the self-propelled mower, built from its own stated figure, so it should not be read as the push mower’s number with a different label.

Checking the assumption against another listing

EGO’s self-propelled 21-inch mower is stated at up to 60 minutes with its 7.5Ah pack, which is 420 Wh on the chart. The push mower’s 45 minutes, scaled to 420 Wh, gives 67.5 minutes. That is 7.5 minutes more than the self-propelled listing. The two listings are different mowers, so the gap shows that the proportional rule is rough, not that either figure is wrong.

Dividing each stated run time by its Wh gives a second view. The push mower works out to 45 / 280 x 100 = 16.1 minutes per 100 Wh. The self-propelled mower works out to 60 / 420 x 100 = 14.3 minutes per 100 Wh. The listings do not explain the difference, so do not use either ratio as a universal rate.

Why the Ryobi figure stays out of the calculation

Ryobi’s kit is stated at up to 80 minutes with two 40V 6Ah batteries. The listing states the pack count and the Ah rating, but it does not state a Wh figure for the batteries. Without a stated Wh, the scaling step has no input from the maker, so this guide does not scale the Ryobi figure. If you want to compare it with another kit, first find each maker’s Wh figure and its voltage basis. For the voltage basics behind those figures, read lawn mower battery voltage and amps. For a self-propelled option with its own battery listing, see DeWalt self-propelled cordless lawn mower. To check whether a battery and charger come with a mower before you compare run times, see cordless lawn mower with battery and charger.

How we chose

We opened nine pages and cite all nine. Three EGO mower or kit pages supply the stated run times. EGO’s battery chart supplies the Wh figures for each Ah rating. The Ryobi kit page supplies the one non-EGO runtime. The Husqvarna chart supplies the point that run time depends on the task. EPA, OSHA and DeWalt’s safety article supply the storage and damage points. We did not use retail listings, review sites or blogs. The pages were opened on 2026-10-22. The sources are not ranked against each other.

What we could not verify

The listings do not state the conditions behind their run time figures, so we cannot say whether a figure assumes a particular grass height or slope. The EGO push and self-propelled figures come from different mowers, so they cannot be used as a direct check of the scaling step. No Wh figure is stated for the Ryobi batteries, and the Select Cut listing states no run time for its two-6Ah kit.

What the sources do not say

  • The sources do not give run time figures for grass height, cutting height, slope or wet grass.
  • The sources do not say that run time scales with watt-hours, so the scaling step is an assumption in this guide.
  • The Husqvarna chart is for Husqvarna tools and does not give a mower run time in this guide.
  • The sources do not state a run time for the EGO push mower with a 6.0Ah or 7.5Ah pack, so those rows are estimates.

FAQ

How do I estimate mower runtime from battery specs?

Start with the run time the maker states for the same mower and pack. Find the Wh figure for that pack and for the pack you plan to use. Multiply the stated run time by the ratio of the two Wh figures. For the EGO push mower, 45 x 336 / 280 gives 54 minutes for the 6.0Ah pack.

Label the result as an estimate. It is not a figure the maker states for that pack.

Is my estimate the same as the manufacturer’s run time?

No. The manufacturer’s figure is a stated run time for one mower and one pack, shown as “up to.” Your figure is a calculation that assumes run time moves in step with stored energy. The sources we opened do not state that rule.

Why use watt-hours instead of Ah for the estimate?

Watt-hours include the voltage, so two packs with the same Ah rating can store different amounts of energy. EGO’s page gives the formula Voltage x Capacity (Ah) = Energy (Wh). Using Wh keeps the scaling step tied to stored energy rather than to the Ah number alone.

Why is my estimate higher than EGO’s self-propelled figure?

Scaling the push mower’s 45 minutes to 420 Wh gives 67.5 minutes. EGO’s self-propelled 21-inch mower is stated at up to 60 minutes with 420 Wh. The two are different mowers, so the rule is rough. Use the stated figure for the mower you are considering when one is available.

Does a bigger pack always mean more run time?

Usually more stored energy gives more run time, and EGO says that choosing a higher Ah rating gives longer run times. Still, run time depends on the mower and the work. The estimate shows the direction of the change, not a guaranteed number of minutes.

Can I use this method for a Ryobi or another brand mower?

Only when the listing states the run time, and the Wh figure or the volts and Ah needed to calculate it. The Ryobi kit page states up to 80 minutes with two 40V 6Ah batteries, but it does not state a Wh figure, so this guide does not scale it.

Bottom line

Scale a runtime only from a figure the maker states for the same mower and pack, use watt-hours for the ratio, and label the result as your estimate.

Sources

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