Things You'll Need
Measuring Stick or Tape Measure
Typically, when you are manually digging a hole with a shovel or spade, the rate at which each shovel load is removed from the ground will change as the digger becomes more tired as well as changes in the soil due to buried rock or plant roots. Therefore, it would be wise to factor in an additional 20 percent if these scenarios could present themselves. For example, a hole estimated to be dug in 41 minutes should actually be planned to take closer to 49 minutes -- 41 multiplied by 0.2 equals 9.2 additional minutes.
Determining the amount of time needed to dig a hole is a calculation that could be applied to a task as small as digging a hole for a fence post or a larger project such as digging out a garden or the placement of a ground-level patio. While the calculation for this task is fairly straightforward, the actual task of digging the hole at the calculated rate will be the greatest challenge.
Measure and write down the number of feet in the length, width and depth of the hole to be dug.
Multiply the length by the width and then multiply that number by the depth. The product of this calculation is the amount of cubic feet of dirt to be removed.
Place a shovel full of earth into a box to determine the volume of dirt removed by each shovel load. Depending on the size of each shovel load, the box could be as small as a shoe box or as large as a milk crate. The goal is to get a full shovel load into a box so that you can measure the depth of the dirt. It should not be too thinly spread out nor overflowing the box.
Spread the dirt evenly in the box, and measure and multiply the length by width by depth in inches. Divide that product by 1728 -- one cubic foot equals 1728 cubic inches. Because each shovel load will be slightly different in volume, it is wise to repeat this process three times and divide the results by three to find the average volume of a shovel load.
Divide the hole volume by the shovel volume. This result is the number of shovel loads needed to complete the task. If each shovel load is 0.5 cubic feet and you need to dig out 50 cubic feet, the number of shovel loads needed will be 100 -- 50 cubic feet to move divided by 0.5 cubic feet per shovel load.
Dig three shovel loads of earth and use a timer to determine how long it takes to complete the three loads. Divide that number by three to get the average time each shovel load will take to complete. Each load will be measured in seconds.
Multiply the number of shovel loads needed to complete the hole by the amount of time just calculated to dig each shovel load. Divide that product by 60 to determine the number of minutes and the result will be the amount of time needed to dig a hole. For example, if the average shovel load took 25 seconds to complete and there will be 100 shovel loads needed to complete the project, the time to complete the hole will be about 41 minutes and 40 seconds, because 25 seconds by 100 loads equals 2500 seconds total; divide by 60 seconds in one minute to calculate the total time of 41.667 minutes.
Christian Zimmerman is a part-time freelance writer and blogger who has been writing regularly since 2007. His primary topics of expertise are in the areas of diet and exercise, sports and computer-related topics. His past articles can be found online at glapple.com and other websites. Zimmerman graduated with an Associate of Applied Science degree in 1989.