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Example data
| Scenario | Shape | Dimensions | Depth | Waste | Compaction | Bag size | Volume (yd³) | Bags |
|---|---|---|---|---|---|---|---|---|
| Front bed | Rectangle | 12 ft × 6 ft | 3 in | 10% | 5% | 2 ft³ | 0.78 | 11 |
| Tree ring | Circle | 10 ft diameter | 2.5 in | 8% | 5% | 2 ft³ | 0.62 | 9 |
| Corner patch | Triangle | 8 ft base, 5 ft height | 4 in | 12% | 6% | 1.5 ft³ | 0.39 | 8 |
Formula used
- Area depends on shape:
Rectangle:
A = L × W· Circle:A = π × r²· Triangle:A = (b × h) / 2 - Base volume:
V = A × D(area × depth) - Adjusted volume:
Vadj = V × (1 + waste) × (1 + compaction) - Conversions:
yd³ = ft³ / 27·liters = ft³ × 28.3168 - Bags needed:
bags = ceil(Vadj / bagVolume)
How to use this calculator
- Select the shape that best matches your mulch area.
- Choose a unit for your measurements and enter dimensions.
- Set your target mulch depth and adjust waste/compaction.
- Enter the bag size you plan to purchase.
- Optionally choose a mulch type to estimate delivery weight.
- Press Calculate to see volume, yards, liters, and bags.
- Use Download CSV or Download PDF to save results.
Depth targets for common garden uses
Mulch depth is a performance setting. For most ornamental beds, 2–3 inches reduces evaporation and moderates temperature while still allowing air to reach roots. Use about 2 inches around seedlings and shallow crowns. For paths or heavy weed pressure, 3–4 inches performs better. Avoid more than 4 inches, especially in wet sites.
Area inputs that match real bed geometry
Choose the closest shape for your space: rectangles for long strips, circles for tree rings, and triangles for corners. Enter measurements in feet, inches, meters, or centimeters; dimensions are converted before the area is calculated. For irregular beds, split the outline into smaller shapes and sum results, or enter a mapped total using Custom area in ft² or m².
Volume outputs for delivery and bag planning
Results are reported in ft³, yd³, and liters to match suppliers and retail packaging. Bulk mulch is commonly sold by the cubic yard, and 1 yd³ = 27 ft³. Bag counts are rounded up using your selected bag size, helping prevent shortages when coverage changes with texture and moisture.
Waste and compaction settings that improve accuracy
Spreading is rarely uniform. Waste covers spillage, edges, and small overbuild; 8–15% is a practical range for many beds.
Compaction reflects settling after rain and watering; 3–8% is typical.
Adjusted volume is computed as Vadj = V × (1 + waste) × (1 + compaction), producing a purchase-ready quantity.
Example data for a common purchase decision
Example: a 120 ft² bed at 3 inches depth. Base volume is about 30.0 ft³. With 10% waste and 5% compaction, adjusted volume is about 34.7 ft³ (about 1.28 yd³). With 2 ft³ bags, plan for 18 bags.
- 120 ft² at 3 in → ~34.7 ft³ adjusted
- Adjusted volume → ~1.28 yd³ (bulk order)
- 2 ft³ bags → 18 bags (rounded up)
FAQs
What mulch depth is typical for landscape beds?
Most beds perform well at 2–4 inches. Use 2 inches near crowns or seedlings, and 3–4 inches where weed pressure is higher. Avoid piling mulch thickly against stems.
Why does the calculator ask for waste and compaction?
Spillage, uneven grade, and settling change the final depth. Waste (often 8–15%) and compaction (often 3–8%) help your estimate match what you will actually spread after watering.
Can I enter area directly instead of dimensions?
Yes. Choose Custom area and enter ft² or m². This works well when you have a site plan, a measuring wheel reading, or area from mapping tools.
How does bag size affect the result?
Bag count equals adjusted volume divided by the bag volume, rounded up. If your retailer uses liters, select liters so the calculator converts to cubic feet accurately.
Is the weight estimate required?
No. Volume drives coverage. Density only helps estimate weight for hauling limits or delivery planning. If you do not need weight, leave density as-is or blank.
What if my mulch area is irregular?
Split the area into rectangles, circles, and triangles, then add the volumes. Alternatively, estimate total area and use Custom area for a fast approximation.
Should mulch touch tree trunks or plant stems?
Keep mulch 2–3 inches away from trunks and stems. This reduces rot risk, improves airflow, and discourages pests. Build a flat “donut,” not a mound.