Flower Bed Calculator: How Many Plants for My Border?
Borders look best layered: tall plants at the back, medium plants in the middle and low edging at the front. Each layer needs its own spacing, which makes counting plants fiddly.
Runs in your browser. Nothing you enter is stored.
What this calculator does
Enter the bed size and how much of it each layer takes, with a spacing for each. The calculator counts plants per zone and in total and draws the bed from back to front.
How to use the flower bed plant calculator
- Enter the bed length and depth from front to back.
- Set the share of the depth for tall, medium and edging plants; they should total 100%.
- Set a spacing for each zone, using plant labels as a guide.
- Read the plants per zone and the total.
- Buy in odd-numbered groups of the same plant for a natural look.
How the calculation works
zone area = bed area × zone share plants in zone = ceil(zone area ÷ spacing²) total = sum of zones
Each zone is treated as a block planted at square spacing, which suits informal borders. For an island bed, put the tall zone in the middle instead.
Worked example
A 4 × 1.5 m border split 30:40:30 needs 9 tall plants at 45 cm, 27 medium plants at 30 cm and 80 edging plants at 15 cm: 116 plants.
Assumptions and limitations
- Spacing guides assume plants at their mature spread; young plants look sparse at first.
- For bedding schemes, closer spacing gives an instant effect.
- Perennials often fill in over two to three seasons.
Frequently asked questions
How many plants do I need for a flower bed?
Multiply the bed area by the plants per square metre or foot for each type's spacing. This calculator splits it into back, middle and front zones.
How far apart should bedding plants be?
Many bedding plants are spaced 15–25 cm (6–10 in) apart; check the label.
Should I plant in odd numbers?
Groups of three, five or seven usually look more natural than even numbers.
How do I design a layered flower border?
Put tall plants at the back, medium in the middle and low edging at the front, repeating plants along the length for rhythm.