Planning a garden space often requires you to figure out the plant density for the area. This preparation is not difficult and gives you a realistic estimate of how many plants to order---preventing you from ordering too few plants and ending up with larger gaps than expected, or too many, resulting in future thinning.
Determine how much space each plant needs. For instance, if you plant violets and the directions tell you to keep them 6 inches apart, you know that 6 inches is the space required, no more and no less.
Measure the planting area. Take the length times the width to get the square footage. So, a 10-foot-by-3-foot bed would total 30 square feet.
Calculate how many plants will fit into the area. If violets need a 6-inch space for each plant, make sure you allot enough space for planting. Think of a 1-square-foot tile and realize you can fit four 6-square inch sections in that square. Multiply the number per square foot by the number of square feet of measured space. For example, if you have 30 square feet of space to work with, multiply 4 times 30---and you'll discover you can plant 120 plants.
For uneven measurements, use this formula: space divided by 12 inches squared = the number of plants per square foot.