Maybe you're asking yourself, how much can I plant? How much area do I need? How much of that monster pile of compost or soil to I actually need?
To determine how many plants you can fit use formula:
Square footage x Spacing factor = quantity of plants
Let's take for example, I have a garden area that is 8 feet wide and 20 feet long. I'm interested in planting some squash and cucumber. According to the seed packet or pot they should be planted at 18" on center.
160 square feet (8x20) x .42 (spacing factor) = 67 total plants
If you've ever been to a mulch or soil yard, it can be very intimidating to guess how much of the huge pile you want in your pickup truck or trailer. Use this formula to gain some confidence in your numbers. (You might want to ask if they deliver...compost mixed soils and especially sand are very heavy. I have compromised the suspension in my pickup truck trying to be overly ambitious!)
Use this formula for cubic yards of mulch, soil, compost, etc.
Square footage x depth factor = cubic feet/27 (3'x3'x3') = cubic yards
We will continue with the example as above. My native soil is pretty pathetic and I want to till in some compost to amend the soil. (This is a great way to get your plants adapted to the native soil. It will provide nutrients for establishment and allow the roots time to strengthen before they enter the native soil.) A healthy 6 inches of compost will be adequate for me to till in this season.
160 square feet (length x width) x .5 (depth factor) =80 cubic feet / 27 = 2.97 cubic yards of compost.
Happy Backyard Farming!