Mulch Calculator
Calculate how much mulch you need in cubic yards and standard 2 cu-ft bags from garden bed area and desired depth.
How It's Calculated
Formula
\text{volume}_{ft^3} = \text{area}_{ft^2} \times \frac{\text{depth}_{in}}{12} \\ \text{yd}^3 = \frac{\text{volume}_{ft^3}}{27} \\ \text{bags} = \left\lceil \frac{\text{volume}_{ft^3}}{2} \right\rceilThis calculator finds mulch volume by multiplying garden bed area (in square feet) by depth (in inches, converted to feet by dividing by 12). The result is converted to cubic yards (dividing by 27, since there are 27 cubic feet in a cubic yard) and to a whole number of standard 2 cubic-foot retail mulch bags, rounded up since you can't buy a fraction of a bag.
Worked Examples
324 ft² bed, 3 in depth
- Volume = 324 x 3 / 12 = 81 ft³
- Cubic yards = 81 / 27 = 3 yd³
- Bags = ceil(81 / 2) = 41
100 ft² bed, 2 in depth
- Volume = 100 x 2 / 12 = 16.67 ft³
- Cubic yards = 16.67 / 27 ≈ 0.617 yd³
- Bags = ceil(16.67 / 2) = 9
Frequently Asked Questions
Why is 81/2 = 40.5 rounded up to 41 bags?
A partial bag still needs to be purchased as a whole bag, so the bag count is always rounded up to the next whole number to make sure you have enough mulch.
What depth of mulch should I use?
2 to 3 inches is a common depth for most garden beds — thick enough to suppress weeds and retain moisture without smothering plant roots.
Why cubic yards instead of cubic feet?
Bulk mulch is typically sold and delivered by the cubic yard, so this calculator converts the raw cubic-foot volume into cubic yards for easy ordering, alongside a bag count for bagged mulch.