MetraNestUse the diameter, not the radius
The diameter runs through the centre from edge to edge and is twice the radius. Enter diameters in metres. For a full disc, leave the central diameter at zero. For a ring, measure the circular area to exclude; its diameter must be smaller than the outer diameter.
Convert area to volume
A layer of 1 cm over 1 m² represents 10 L. The calculation therefore multiplies the area by the depth in centimetres, then by 10. The depth remains your choice. If it is zero, the area remains available but no material purchase is calculated.
Compare the requirement with whole bags
The allowance is added to the volume before rounding up to whole bags. The purchased volume may therefore exceed the requirement including the allowance. The calculation assumes an even layer and a circular central area; it does not account for settling, uneven ground or other obstacles.
Area = π × (outer diameter² − inner diameter²) ÷ 4. Volume in L = area in m² × depth in cm × 10.
A ring with a chosen allowance
With diameters of 4 m and 2 m, the area is 3π, or approximately 9.425 m². A layer of 5 cm represents approximately 471.239 L. With a 10 % allowance, the requirement reaches approximately 518.363 L: 11 bags of 50 L provide 550 L purchased.
Details to check
- Convert centimetres to metres for the diameters.
- Measure areas with different layer depths separately.
- Use the actual capacity of your bags.
Frequently asked questions
How do I calculate a disc without a central hole?
Enter zero as the central diameter. Only the area of the outer disc is then used.
Can I calculate just the area?
Yes. Enter a depth of zero. The primary result remains the area; volumes and the number of bags are zero.
A method you can check · Content review :
Each tool shows its formulas and assumptions. Worked examples let you repeat the calculation and understand how rounding works.