Calculation history
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Formula used
How to use this calculator
Measure each garden section at ground level. Choose the closest matching shape. Add extra sections for complex layouts.
Enter patios, sheds, ponds, and paths as exclusions. Allocate the remaining area by percentage or area. Keep all allocations within the usable total.
Add materials using coverage, rate, or depth. Include waste and unit costs. Review quantities before ordering supplies.
Worked example
| Item | Input | Calculation | Result |
|---|---|---|---|
| Main garden | 12 m × 8 m | 12 × 8 | 96 m² |
| Patio exclusion | 4 m × 3 m | 4 × 3 | 12 m² |
| Net area | 96 m² − 12 m² | Gross − exclusions | 84 m² |
| Topsoil at 50 mm | 84 m² × 0.05 m | Area × depth | 4.2 m³ |
Measuring irregular gardens
First, split the boundary into rectangles, triangles, and circles. Measure each part separately. Add or subtract those parts in the calculator.
Alternatively, record boundary points from a consistent origin. Enter each point as x,y coordinates. Keep the points in boundary order.
Avoid crossing boundary lines between coordinate points. Overlapping sections can inflate the result. Check the sketch before purchasing materials.
Frequently asked questions
What is gross garden area?
Gross area includes every measured garden section. It does not deduct patios or buildings. Use exclusions to find usable space.
What is net usable area?
Net area equals gross area minus excluded features. It represents the remaining workable garden surface. Material estimates usually use this value.
Can I calculate an L-shaped garden?
Yes. Enter the outer rectangle and rectangular cut-out. The calculator subtracts the cut-out automatically.
How do polygon coordinates work?
Enter points in boundary order using x,y pairs. Separate pairs with semicolons or new lines. Three points are required.
Should paths be exclusions or allocations?
Use exclusions when paths are outside the usable plan. Use allocations when paths belong inside the planned net area.
How much waste should I add?
Five to ten percent suits many regular projects. Complex cuts may need more allowance. Supplier guidance should take priority.
Why are some perimeters unavailable?
Base and height do not define every side. Triangles and trapezoids need extra sides for exact perimeter. Their areas remain accurate.
Can I estimate topsoil or mulch?
Yes. Choose the depth method and enter application depth. Add package size to estimate bag quantities.
Can different sections use different units?
Yes. Each section and exclusion has its own length unit. Results convert into your chosen area unit.
Does the cost estimate include tax?
Tax is optional and applied after other costs. Enter the required percentage for your project. Currency defaults to British pounds.
Are estimates suitable for ordering?
The results support planning and comparison. Real gardens contain slopes and measurement uncertainty. Confirm final quantities with suppliers.