Mulch Calculator
Enter your bed size and desired depth to instantly calculate how many bags of mulch or how many cubic yards you need for delivery.
Measure or estimate your total area in square feet and enter it directly.
Bag size
Enter your dimensions above to see results
How to Use This Calculator
Select the shape of your mulching area at the top. Use Rectangle for straight-edged beds and borders, Circle for tree rings and round garden beds, or Irregular to enter your own square footage if you've already measured a complex-shaped area.
Enter your dimensions in feet, inches, meters, or centimeters — whatever is easiest to measure in. Set the Depth field to how thick you want the mulch layer. The calculator defaults to 3 inches, which is the standard recommendation for most landscape beds. Adjust to 2 inches for light top-dressing or 4 inches for maximum weed suppression.
Choose a Bag size to see the exact number of bags you'll need. Most hardware stores sell mulch in 2 cu ft bags; landscape supply yards often sell in 3 cu ft bags. Select "Bulk" if you're ordering loose mulch by the cubic yard — you'll see the cubic yard total to share with your supplier.
Results update as you type. The bag count always rounds up to the next whole bag, since you cannot buy a fraction of a bag. If you have mulch left over, use it to top-dress thin spots or extend coverage under shrubs and around tree rings.
Formula
The mulch formula converts your surface area and depth into a volume, then divides by bag size to get the number of bags needed.
Rectangle area Area (sq ft) = Length × Width Circle area Area (sq ft) = π × (Diameter ÷ 2)² Volume Volume (cu ft) = Area × (Depth in inches ÷ 12) Volume (cu yd) = Volume (cu ft) ÷ 27 Bag count Bags = ⌈ Volume (cu ft) ÷ Bag size (cu ft) ⌉
One cubic yard equals 27 cubic feet — a crucial conversion since mulch volume is calculated in cubic feet but sold by the cubic yard in bulk. A 10×20 ft bed at 3 inches deep is: 200 sq ft × 0.25 ft = 50 cu ft. That's 50 ÷ 27 = 1.85 cubic yards, or 50 ÷ 2 = 25 bags of 2 cu ft mulch.
Bag counts use the ceiling function — they round up to the next whole bag. You cannot purchase 0.7 of a bag. When ordering bulk mulch, consider rounding up to the nearest quarter-yard, since most suppliers have a minimum delivery and you'd rather have a little extra than run short mid-project.
Mulch compresses slightly over time as it weathers and decomposes. A 3-inch application may settle to 2 inches after a growing season — which is also part of what improves your soil over time. Plan to top-dress annually at 1–2 inches to maintain consistent depth and weed suppression year after year.
Common Project Sizes
Recommended depths: 2–3" for flower beds, 3–4" for tree rings, 4" for weed suppression. No waste factor applied.
| Area Size | Depth | Cubic Yards | 2 cu ft Bags | 3 cu ft Bags |
|---|---|---|---|---|
| 10 × 10 ft (100 sq ft) | 2" | 0.62 | 9 | 6 |
| 10 × 10 ft (100 sq ft) | 3" | 0.93 | 13 | 9 |
| 10 × 20 ft (200 sq ft) | 3" | 1.85 | 26 | 17 |
| 15 × 20 ft (300 sq ft) | 3" | 2.78 | 38 | 25 |
| 20 × 20 ft (400 sq ft) | 3" | 3.70 | 50 | 34 |
| 20 × 20 ft (400 sq ft) | 4" | 4.94 | 67 | 45 |
| 20 × 40 ft (800 sq ft) | 3" | 7.41 | 101 | 67 |
Frequently Asked Questions
How deep should I apply mulch?
Flower beds and vegetable gardens: 2–3 inches. Tree rings and shrubs: 3–4 inches (pull mulch 6 inches back from the trunk to prevent rot). Weed suppression: 4 inches minimum — anything thinner lets light through and weeds still germinate. Don't exceed 4 inches in most cases; deep mulch can suffocate roots and create a habitat for pests. The default in this calculator is 3 inches, which works well for most general landscaping.
How many bags of mulch equal a cubic yard?
One cubic yard equals 27 cubic feet. A 2 cu ft bag fills 1/13.5 of a cubic yard, so you need roughly 13–14 two-cubic-foot bags per cubic yard. For 3 cu ft bags, you need about 9 bags per cubic yard. For 1 cu ft bags (common at hardware stores), you need 27 bags. Bulk mulch by the cubic yard is almost always cheaper per cubic foot once you're covering more than a few hundred square feet.
When is the best time to apply mulch?
Spring is the most popular time — soil has warmed up and you're ahead of the weed season. Apply after your last frost but before summer heat sets in. A second application in fall helps moderate soil temperature and retain moisture heading into winter. Avoid applying mulch when the ground is frozen, as it insulates the frost and delays spring warm-up.
What type of mulch should I use?
Shredded hardwood mulch is the most versatile — it decomposes slowly, improves soil, and stays put in rain and wind. Pine bark nuggets work well in beds with good drainage but can float in heavy rain. Cedar mulch has natural pest-repellent properties. Straw and pine straw are good for vegetable gardens and slopes. Rubber mulch lasts longer but doesn't improve soil. For this calculator, all types calculate the same volume — the formulas don't change by material.
How much area does one cubic yard of mulch cover?
One cubic yard covers approximately 108 sq ft at 3 inches deep, 81 sq ft at 4 inches deep, or 162 sq ft at 2 inches deep. A simple rule: divide 324 by your depth in inches to get square feet per cubic yard. For example, at 3 inches: 324 ÷ 3 = 108 sq ft.
Do I need to add a waste factor for mulch?
Mulch waste is minimal compared to materials like concrete or gravel — you're spreading a flexible material with no rigid form to fill. This calculator intentionally omits a waste factor. If your bed has complex curves or obstacles, round up to the nearest half-yard when ordering bulk. For bagged mulch, round up to the next full bag — any extra can be used to top-dress thin spots.
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