The Bales of Straw Needed to Mulch an Irregular Area calculators computes the number
AREA COVERED of regular square-bales of straw or hay needed to cover an area such as a field, garden or planter to a depth adequate to suppress the growth of grass and weeds. To compute the Bales of Straw Needed to Mulch a Rectangular Area, CLICK HERE.
INSTRUCTIONS: Choose your length units and enter the following:
- (a) The length of side a of your four sided area.
- (b) The length of side b of your four sided area.
- (c) The length of side c of your four sided area.
- (d) The length of side d of your four sided area.
- (D) The length of the diagonal of your four sided area (see diagram).
The Bales of Straw Need to Mulch an Irregular Area calculator will then compute the area in square feet and divide by the number of square feet covered in a single bale of straw. This will result in the total number of bales needed for ground cover of the area.
Considerations
Mulching is different than ground cover for planting. For mulching, one wants to suppress the growth of grass and weeds. For ground cover, one wants to protect grass seed and young seedlings to encourage grass growth and moisture retention. The differences is in the depth of the straw laid. This calculator computes straw deep enough to suppress weed growth.
- Mulch to Cover Area: Enter an area size (e.g. 45 square feet or 0.75 acres) and depth of mulch wanted, and see estimated amount of mulch needed.
- Mulch to Cover Circular Area: Enter the diameter (D) of the circle and depth of mulch wanted, and see estimated amount of mulch needed.
- Mulch to Cover Rectangular Area: Enter the length (L) and width (W) of the area and depth of mulch wanted, and see estimated amount of mulch needed.
- Mulch to Cover Irregular Area: Enter the length of the four sides (a,b,c,d) and the diagonal (D) of an irregular area (see diagram) and the depth of mulch wanted, and see estimated amount of mulch needed.

- Mulch Cost Estimate: Enter the amount of mulch needed, choose a type of mulch and it will provide an estimate of the cost.
- Mulching With Straw (Irregular Area): Enter the length (L) and width (W) of the rectangular area and it will estimate the number of bales of straw needed to mulch the area with straw.
- Mulching With Straw (Area): Enter the area (acres, square feet) to see an estimate of the number of bales of straw needed to mulch the area with straw.
- Bulk vs Bag Price Comparison: Enter the bulk mulch and bag prices and volumes, and it tells you which is cheaper and by how much.
- Garden Area (Irregular): Many gardens have four straight sides. This calculator lets you enter the lengths of the sides (a,b,c,d) and the diagonal (D) to compute the square footage of the garden.

Mulch Pricing
You should always use the locally available pricing when computing your costs. However, for your convenience a periodic survey is made on the Internet for mulch prices in the United States. The most recent observations are as follows:
- Date: 12/27/21
- Store: Lowes
- Red Mulch: 1.84 USD/ft³
- Pine Mulch: 2.44 USD/ft³
- Common Hardwood Mulch: 1.84 USD/ft³
- Cedar Mulch: 1.83 USD/ft³
- Rubber Mulch: 8.725 USD/ft³
See Also