Mulch Calculator
Bag quantities and bulk volume from bed dimensions and mulch depth.
Project inputs
Examples
Supplier prices (optional)
Prices exclude delivery, tax and labor. Currency changes labels only.
Estimate
Start with your measurements.
Your order quantity, purchasing options and material cost appear here.
Overage is included in purchasing quantities. Check product yields before ordering.
Check product yields and project specifications. Material subtotals exclude delivery, tax, labor and equipment. These quantities do not specify structural dimensions or reinforcement.
Estimate
Worked example
Here is a step-by-step walkthrough for a 20 × 5 ft garden bed at 3 inches deep using standard 2 cu ft bags.
- Step 1; Area 20 × 5 = 100 sq ft
- Step 2; Volume 100 × (3 ÷ 12) = 25 cu ft
- Step 3; Add 5% Waste 25 × 1.05 = 26.25 cu ft
- Step 4; Cubic Yards 26.25 ÷ 27 = 0.97 cu yd
- Step 5; Bags Needed 26.25 ÷ 2 = 14 bags
- Step 6; Cost at $4.99/bag $69.86 in bags vs ~$34 in bulk
Calculation method
The calculator multiplies your bed area (length × width) by your desired mulch depth, converting everything to cubic feet. It adds your waste factor, divides by bag size for bag count, and multiplies cubic yards by bulk price for the bulk estimate.
One cubic yard is 27 cubic feet. For at least one yard, buy 14 whole 2-ft³ bags or 9 whole 3-ft³ bags before adding overage. Compare your bag and bulk quotes including delivery.
Pro tip: If you have multiple beds, run the calculator once per bed and add the totals together; or combine them into a single total square footage for a one-shot estimate.
Mulching Tips for Better Results
- The ideal depth is 2–3 inches. Less than 2 inches won't suppress weeds effectively. More than 4 inches can suffocate roots and cause stem rot, especially in wet climates.
- Keep mulch away from stems and trunks. The classic "mulch volcano" (piled against tree bark) causes rot and disease. Keep at least 3–4 inches of clearance around tree bases.
- Apply in late spring. After the soil has warmed, mulching locks in warmth, moisture, and keeps weeds down through summer. Fall is also good for insulating root systems through winter.
- Weed first. Pull all visible weeds before mulching. Newspaper or cardboard laid underneath adds extra weed suppression; effective and free.
- Refresh, don't just add. If you already have mulch in the bed, rake it up and see how much remains. You often only need 1 inch to refresh, not a full new layer.
Common Mulching Mistakes
Too much mulch. More than 4 inches blocks water and air from reaching roots. It can also harbor pests and disease. Stick to 2–3 inches maximum in most situations.
Mulching against stems. Piling mulch against plant stems or tree trunks causes rot, disease, and pest problems. Always maintain a clear 3-inch gap at the base.
Using dyed mulch near vegetables. Some dyed mulches (particularly black or red) come from recycled wood that may contain chemicals. Use natural, undyed mulch in vegetable and edible gardens.
Not accounting for settling. Mulch compresses over time. What starts at 3 inches may settle to 1.5–2 inches within a season. Plan to top up annually.
Assumptions
- ◦Volume conversion: 1 cubic yard = 27 cubic feet. All depth inputs in inches are converted to feet (divide by 12) before calculation.
- ◦Bag sizes: Standard 2 cu ft bag = 13.5 bags/yd³; 3 cu ft bag = 9 bags/yd³; 1.5 cu ft bag = 18 bags/yd³.
- ◦Waste factor: Default 5% covers spreading variation and irregular bed shapes. Increase to 10% for very uneven ground.
- ◦Prices: Enter supplier prices. The examples are arithmetic illustrations, not current price quotes.
- ◦Results are estimates: Actual coverage varies by mulch type, moisture, and how evenly it is spread. Confirm quantities with your supplier.