Mulch Calculator

Mulch is sold by the bag or by the cubic yard (bulk delivery), and figuring out the right amount is one of the most common landscaping calculations. Too little mulch and weeds return quickly. Too much and you risk smothering plant roots or trapping moisture against stems. The standard recommendation for landscape mulch is a depth of 2 to 4 inches. Two inches suppresses most weeds in established beds. Three inches is the typical target for new planting areas. Going deeper than 4 inches can reduce soil aeration and cause root problems. This calculator works in both imperial and metric units. For imperial, enter length and width in feet and depth in inches. For metric, enter length and width in metres and depth in centimetres. Results include cubic yards, cubic feet, and cubic metres, plus the number of standard-size bags needed so you can compare bulk delivery cost against buying bags.

• Flower bed mulching: Calculate the mulch needed for planting beds around the house. Use 3 inches depth to suppress weeds and retain moisture through summer.
• Tree ring coverage: A mulch ring around a tree should be 3 to 4 feet in radius and 3 to 4 inches deep. Break the ring area into a rough rectangle for a quick estimate, or use a circle area formula (pi × r²) as the input area.
• Bulk delivery planning: One cubic yard covers about 100 sq ft at 3 inches deep. Use the cubic yard result to compare the cost of bulk delivery (typically sold by the yard) against buying individual bags.
• Annual bed refresh: Existing mulch breaks down by 1 to 1.5 inches per year. To top up to a target depth, enter only the top-up depth (target depth minus remaining depth) to find the additional volume needed.

• Mulching too deep: More than 4 inches of mulch can prevent water from reaching roots, cause stem rot, and create a habitat for rodents. Three inches is the standard maximum for most plants.
• Forgetting to convert depth to the same unit: The calculator handles the unit conversion internally. If you use the imperial option, enter depth in inches (not feet). Entering 3 feet instead of 3 inches gives 36 times the required volume.
• Not accounting for irregular shapes: The calculator assumes a rectangle. For curved or irregular beds, break the area into rough rectangles or estimate the overall bounding rectangle and reduce the result slightly.
• Ignoring existing mulch depth: If there is already 1 inch of old mulch, you only need to add enough to bring the depth up to target. Enter the top-up depth, not the full target depth.

1. 1Select imperial (feet/inches) or metric (metres/centimetres) as the input unit.
2. 2Enter the length and width of the area to be mulched.
3. 3Enter the desired mulch depth.
4. 4For imperial: depth is converted from inches to feet, area times depth gives cubic feet, then divided by 27 for cubic yards.
5. 5For metric: depth is converted from centimetres to metres, and area times depth gives cubic metres.
6. 6Bags needed are calculated by dividing cubic feet by the bag volume (2 or 3 cu ft), rounded up to whole bags.

• One cubic yard covers about 100 sq ft at 3 inches: This rule of thumb is useful for quick sanity checks. If your calculator result gives a very different coverage, re-check your inputs.
• Order 10% extra for delivery shrinkage: Bulk mulch can compact during delivery. Order 5 to 10% more than the calculated volume when ordering by the yard to ensure you have enough after settling.
• Compare bulk vs. bags by cost per cubic foot: A 2 cu ft bag at $4 costs $2 per cubic foot. Bulk mulch at $30/yd³ costs $1.11 per cubic foot. For large areas, bulk delivery is almost always cheaper.
• Apply mulch in spring after soil warms: Applying mulch too early in spring traps cold soil and delays warming. Wait until soil temperature reaches 50°F (10°C) before spreading mulch around new plantings.