Calculation for Purchasing
Packaged Compost

Packaged compost is one of the wonderful products available on the market designed to help make your gardening a little easier.

Knowing how to calculate the number of bags of product you need to cover an area in your garden though, can be a bit overwhelming.

For instance, one of the packaged compost products is available in a 16-quart bag.

Suppose you want to purchase enough compost to cover a garden area roughly 10 foot long by 10 foot wide with compost to a depth of 2 inches.

With a little calculation and conversion you can figure it out easily enough.

First, you'll need to use the mathematical formula for volume: length (L) multiplied by width (W) multiplied by depth (D) or L x W x D.

All of the measurements will be easier to calculate if they are in the same units. Since you want the depth of compost in inches rather than feet, convert the foot measurements of the garden area to inch measurements.

To convert the area that is 10 foot by 10 foot into inch units, simply multiply each foot by 12.

This will give you an area that is 120 inches by 120 inches. Now use the volume formula from above.

For mulch at a depth of 2 inches, the calculation will be 120in x 120in x 2in or 2880 cubic inches.

The compost is packaged in a 16-quart bag. Since there are 4 quarts to a gallon, the 16-quart bag would contain 4 gallons of product per bag.

How many gallons will you need to cover the 2880 cubic inches?

By using an online conversion tool you can determine how many dry gallons are contained in 1 cubic inch. The result is: 1 cubic inch = 0.00372023471 [US, dry] gallons.

You're almost done.

You can round up and use a shorter figure for your final calculation: 2880 cu in x 0.0037 [US, dry] gal = 10.656 gallons of compost will be needed.

Therefore, in order to cover that 10 foot by 10 foot garden area with a 2 inch layer of compost, you'll need about 10-1/2 gallons or almost 3 bags of the packaged product.

When buying and using packaged compost, knowing the math can help make gardening easier.

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