Measure the material footprint

Measure only exposed bed area. Subtract hardscape, large boulders and the open space around plant stems. When refreshing a bed, check how much old mulch remains before choosing a depth. If two inches remain and the plan calls for three inches in total, enter one inch as the added layer. Dividing a curved bed into short rectangles is often easier than estimating its widest bounding box.

University of Minnesota Extension describes a two to four inch surface layer for many garden uses and advises keeping mulch clear of trunks and stems. Account for existing mulch in that total. Ask the supplier whether the product is shredded bark, chips or another blend, then compare bag volume with the loose volume in a bulk load. Keep bags from different products on separate lines if the finish or color needs to match within a bed.

Work through this estimate

Start with the geometry for 20 × 20 ft at 6 in. The footprint is 20 ft × 20 ft, which gives 400 square feet. Convert the depth to the same unit before multiplying. Dividing 6 inches by twelve gives 0.5 feet. The footprint times that depth gives 200 cubic feet in place. Keep the full precision on the worksheet and round only the displayed result. For a tapered section, measure enough cross sections to represent the change in area.

The current worksheet adds 10% for handling and variation. Multiplying the measured volume by 1.1 produces 220 cubic feet to order. Divide that value by twenty-seven to convert to 8.15 cubic yards. A yard is three feet in each direction, which accounts for all twenty-seven cubic feet. If your supplier quotes a different order increment, round the final combined project quantity up to the next increment it actually sells.

For weight, the model uses 800 pounds per cubic yard. Applying that density to the order gives 6519 pounds. Dividing by two thousand gives 3.26 US short tons. Treat weight as a planning estimate. Moisture, source material and packing affect actual loads. Obtain the supplier’s density before using a takeoff to plan hauling, and use the carrier’s verified payload limits when arranging delivery.

Compare the purchase units

One 2 cu ft bag covers 2 cubic feet under this model. Dividing the unrounded order volume by the bag yield and rounding upward gives 110 bags. Look at the measured yield on the product label when changing brands. A bag’s weight and the volume it contributes to the finished job describe different quantities. If the store stocks multiple sizes, each row is a complete alternative for the same job. Choose one size or prepare a separate mixed-size order.

The bulk allowance uses $38.00 per cubic yard and a delivery fee of $125.00. For this worksheet that gives $434.63 delivered, compared with $590.52 for the least expensive bag option. Get an itemized local quote covering minimum loads, delivery distance, tax and placement. Include any equipment or extra trips in your own comparison. A small change in the delivery charge can reverse the result on a modest job.