Measure several garden beds for one mulch order
Calculate the volume of each section, add the volumes, then round the combined order. This avoids buying an extra fraction of a bag for every separate bed.
Multiple-bed worksheet
Enter rectangular sections and the depth to add to each. Measurements are feet; depth is inches. For curved beds, see the shape examples below.
Values stay in this page and reset when you reload. Print to keep a copy. Zero depth means that section needs no new mulch.
Measure the area that will actually get mulch
- Sketch the bed and divide it into simple shapes. Avoid counting overlapping corners twice.
- Measure along the ground where practical. Use consistent feet, converting 6 inches to 0.5 feet rather than writing 0.6.
- Exclude paths, patios and other uncovered areas. A tree ring should leave the trunk and root flare uncovered.
- Check the existing layer at several points. Split areas with different top-up needs into separate sections.
Rectangle, circle, or ring?
| Shape | Formula | Example |
|---|---|---|
| Rectangle | Length × width | 12 × 8 = 96 sq ft |
| Circle | π × radius² | 10 ft diameter: 78.54 sq ft |
| Ring | π × (outer radius² − inner radius²) | 10 ft outer / 4 ft inner diameter: 65.97 sq ft |
A radius is half the diameter. The ring example subtracts a 2-foot-radius inner opening from a 5-foot-radius outer circle: π × (25 − 4). At 2 inches deep, that ring needs about 11 cubic feet, or 6 two-cubic-foot bags. Use “Known area” in the main calculator for a ring.
Worked example: two different top-ups
Bed A is 12 × 8 feet and needs 2 inches. Bed B is 15 × 4 feet and needs 1 inch.
| Section | Area | New depth | Volume |
|---|---|---|---|
| Bed A | 96 sq ft | 2 in | 16 cu ft |
| Bed B | 60 sq ft | 1 in | 5 cu ft |
| Combined | 156 sq ft | Varies | 21 cu ft |
The order is 21 ÷ 27 = 0.7778 cubic yards, or 11 two-cubic-foot bags. The last bag leaves a theoretical 1 cubic foot over the exact estimate. If Bed B already meets its target, set its added depth to zero; the order then becomes 16 cubic feet, or 8 bags.
Curved edges need an estimate range
For a curved strip, measure its width at evenly spaced points. Average the widths, then multiply by the strip's length as an approximation. A 20-foot strip averaging 3 feet wide is about 60 square feet. If the plausible width is 2.5–3.5 feet, the area range is 50–70 square feet. At 2 inches deep, that is roughly 8.33–11.67 cubic feet, or 5–6 two-cubic-foot bags. Re-measuring may be more useful than adding an arbitrary allowance.
Round only after the total
Three sections needing 5 cubic feet each total 15 cubic feet, requiring 8 two-cubic-foot bags. Rounding each section separately gives 3 + 3 + 3 = 9 bags. Combine only material that is interchangeable: different mulch types or colors should be ordered separately.
Method: original geometry and worked estimates; no claim of on-site measurement. For plant-specific depth advice, see the sourced depth guide. Worksheet and examples checked October 2, 2026.