MEASUREMENTS AND PURCHASE DECISIONS
Calculate mulch top-up from the existing layer.
Why should existing mulch be measured before ordering a new layer?
Use the matching calculator
Use this decision sequence
- Measure each bed separately.
- Record the target and existing layer depths on the same basis.
- Use only the positive depth difference for a top-up.
- Pool compatible top-up volume before allowance and whole-bag rounding.
Keep the quantities distinct
| Quantity or assumption | How to use it |
|---|---|
| New bed | Existing depth is zero. |
| Top-up | Use max(target minus existing depth, zero). |
| Overfilled bed | The top-up volume is zero, not a negative purchase. |
Worked comparison
A 200 ft² bed has an existing 1 in layer and a supplied target of 3 in. The added layer is 2 in: 200 × 2/12 = 33.33 ft³. With 10% allowance and 2 ft³ bags, the order is 19 bags.
Check before using the estimate
Do not order the full target depth again over an existing layer.
All dimensions, product properties, prices and specifications in this example are illustrative arithmetic inputs. Use the values from your measured plan, selected product data sheet and supplier quote. This guide does not choose construction specifications or certify safety.
Calculation and scope checked 2026-10-04. Methods and scope.