What does this calculator do?
It turns the size of a bed into practical numbers: area, perimeter, plant count and soil volume. Use it before buying plants or ordering soil so you do not over- or under-buy.
Formulas used
area = length × widthperimeter = 2 × (length + width)plants = floor(usable length ÷ spacing) × floor(usable width ÷ spacing)soil volume = area × depth
Usable length and width are the bed size minus the border on both sides.
Step-by-step example
A bed is 12 ft × 4 ft, plants go 12 inches apart, and you want 6 inches of soil.
| Step | Calculation | Result |
|---|---|---|
| 1. Area | 12 × 4 | 48 ft² |
| 2. Plants per row and rows | 12 ÷ 1 and 4 ÷ 1 | 12 and 4 |
| 3. Plant count | 12 × 4 | 48 plants |
| 4. Soil | 48 ft² × 0.5 ft = 24 ft³ ÷ 27 | 0.89 yd³ |
Common mistakes
- Using spacing from a different plant than the one you are growing.
- Forgetting paths, which reduce the planting area.
- Entering depth in feet when the field expects inches or centimetres.
How to use this calculator
- Enter your values. Plan a garden bed: area, perimeter, how many plants fit and how much soil to buy.
- Check units and assumptions. Make sure the inputs use the same scale and that any optional settings match your situation.
- Calculate and review. Compare the output with the formula below and note any limitations stated on the page.
Formula and calculation method
For rectangular spaces, calculate length × width × depth after converting all measurements to the same unit. Convert cubic feet to cubic yards by dividing by 27. Add a waste allowance only when appropriate for the material and project.
Worked example
For example, a 10 ft × 8 ft area filled to 1 ft deep is 80 cubic feet. Dividing 80 by 27 gives about 2.96 cubic yards before any allowance for compaction, uneven ground, or waste.
Search and practical tips
People commonly search for a garden size calculator – area & plant count, how to calculate the result step by step, which formula to use, and how to check the answer manually. Use the formula above as a transparent starting point, and consult the relevant institution, agency, or qualified professional when an official rule or personal circumstances affect the result.
Frequently asked questions
How do I calculate the area of a garden bed?
Multiply length by width. A bed that is 12 ft long and 4 ft wide has an area of 48 square feet.
How many plants fit in a bed?
Divide the usable length and width by the plant spacing, round each down, and multiply. At 12 inch spacing a 12 ft × 4 ft bed holds 12 × 4 = 48 plants.
What does the border or path setting do?
It removes a strip along every edge of the bed from the planting area, so plants are not counted where you plan to walk or leave a gap.
How much soil do I need?
Multiply the bed area by the soil depth. The calculator gives cubic yards or cubic metres, which is how bulk soil is sold.
Is plant spacing the same for all plants?
No. Spacing varies by plant and variety, so use the seed packet or plant tag for the right figure and enter it in the spacing field.