How ScapeCalc calculates

Units

Inside every calculator, lengths are in feet, areas in square feet and volumes in cubic feet. What you type is converted on entry, and results are converted for display. Lengths can be typed in feet and inches, such as 6' 6" or 6 ft 6 in, or in meters and centimeters with the metric setting.

Checked October 23, 2026.

Area of each shape

Volume, waste and settling

• Volume of each area = area × depth, with depth converted to feet. Each area can have its own depth.
• Top-up: the depth to add is the target depth minus the existing depth. If the target is not deeper than what is there, no top-up is needed.
• Total = the sum of all complete areas. An area with a missing or invalid field is left out of the total, and the calculator says so.
• Waste and settling allowance: volume to buy = volume × (1 + allowance). The volume before the allowance is shown too.
• Cubic yards = cubic feet ÷ 27. Cubic meters = cubic feet × 0.0283168.

Rounding

• You can't buy part of a bag, so bag counts always round up. The unrounded figure is shown next to the count.
• Bulk orders round up to the supplier's order increment, for example to the next half cubic yard.
• A value that lands a hair above a whole number from floating-point error, such as 4.0000000001 bags, is treated as the whole number.
• Displayed figures are rounded for reading (cubic yards to two decimals). Totals are always calculated from unrounded values.

Bags, bulk and cost

• Bags = volume to buy ÷ bag size, rounded up. Bag sizes in quarts are converted at 25.714 quarts per cubic foot.
• Bag cost = number of bags × price per bag.
• Bulk cost = cubic yards ordered (after rounding up to the order increment) × price per cubic yard + delivery fee.
• Cheaper option: shown only when both a bag price and a bulk price are entered, with the difference in dollars.
• Break-even volume, where bulk becomes cheaper than bags = delivery fee ÷ (price per bag ÷ bag size − price per cubic yard ÷ 27). It is approximate because it ignores rounding, and it is shown only when bags cost more per cubic foot than bulk.

Worked example

A bed 10 ft long and 10 ft wide, at 3 inches deep, with 2 cubic foot bags and no waste allowance. Enter the same bed in the mulch calculator to check it:

1. Area: 10 × 10 = 100 sq ft.
2. Depth: 3 ÷ 12 = 0.25 ft.
3. Volume: 100 × 0.25 = 25 cu ft, which is 25 ÷ 27 = 0.93 cubic yards.
4. Bags: 25 ÷ 2 = 12.5, rounded up to 13 bags.
5. With a 10% allowance: 25 × 1.1 = 27.5 cu ft, which is 13.75, rounded up to 14 bags.

Limits of these estimates

• Results are only as exact as your measurements. Curved or irregular beds are approximated by the shapes you choose.
• Real bags and loads vary. Bag fill, moisture and how loosely a supplier loads bulk mulch all change the volume you get.
• Mulch settles. The waste and settling allowance is a ScapeCalc default, not a measured value for your product.
• Playground depths are the figures CPSC publishes. ScapeCalc has not tested any surfacing product; follow the maker's stated depth and fall height.
• Prices are the ones you enter. ScapeCalc does not look up or store prices.

Sources and check dates

Each calculator lists the constants it uses (bag sizes, depths, densities and allowances) here and on its own page, each with its source and the date it was checked. Defaults with no published standard are labeled "ScapeCalc default". Sources are reviewed on a set schedule: a full review each January before the spring season, and lighter checks in April, July and October. The change log below records only reviews that have been completed.

Mulch calculator constants

The constants behind the mulch calculator, each with its sources:

All sources

Every source the Mulch Calculator relies on, in one numbered list. Government and university extension publications support depths and safety guidance; retailer and product listings support bag sizes and product weights and are labeled as listings; figures ScapeCalc works out itself are labeled as derived or as ScapeCalc defaults.

1. Unit definitions (12 in per ft; 3 ft per yd, so 27 cu ft per cu yd). Checked Oct 23, 2026.
2. NIST Handbook 44 (2026), Appendix C: General Tables of Units of Measurement, National Institute of Standards and Technology. Checked Oct 23, 2026.
3. Mulch category, first page of listings (sample of 30 of 98 products), Ace Hardware. Checked Oct 23, 2026.
4. Bagged wood mulch category, first page of listings (sample of 12 of 33 products), Home Depot. Checked Oct 23, 2026.
5. Scotts Nature Scapes mulch, 2 cu ft, Ace Hardware. Checked Oct 22, 2026.
6. GroundSmart Black Rubber Nuggets, 0.8 cu ft, Ace Hardware. Checked Oct 23, 2026.
7. Rubberific Premium Shredded Rubber Mulch, 0.8 cu ft, Lowe's. Checked Oct 23, 2026.
8. Rubber mulch bulk density, approximate, derived from four product listings. Checked Oct 23, 2026. Kodiak super sack: 2,000 lb ÷ 76.9 cu ft = 26.0 lb/cu ft (https://www.kodiaksports.com/products/rubber-mulch-super-sack-2000lbs). Viagrow pallet: 1,000 lb ÷ 37.5 cu ft = 26.7 lb/cu ft (https://www.homedepot.com/p/Viagrow-Rubber-Playground-and-Landscape-Mulch-37-5-CF-pallet-of-25-bags-1-38-cu-yds-1000-lbs-VRedWRM-25PT/330722224). Rubbermulch.com bag: 40 lb ÷ 1.55 cu ft = 25.8 lb/cu ft (https://rubbermulch.com/pages/calculate-rubber-mulch). Walmart listing: 1,000 lb ÷ 39 cu ft = 25.6 lb/cu ft (https://www.walmart.com/ip/Rubber-Mulch-Nuggets-Protective-Flooring-for-Playgrounds-Swing-Sets-Play-Areas-and-Landscaping-1-000-LBS-39-CU-FT-Black/15637911975). Range 25.6–26.7 across four products. Product-derived; varies by product; not a standard. No manufacturer specification sheet found (Oct 23, 2026); the GroundSmart listings at Lowe’s and Do it Best give no weight. Used only for an optional weight estimate that never changes bag counts.
9. Rubber Mulch Use in Home Gardens and Landscapes (FS163E), Linda Chalker-Scott, Washington State University Extension (archived publication) (PDF). Checked Oct 23, 2026. Archived by WSU; revised Dec 2021. Archived is not withdrawn: its points are corroborated by UNL EC1274 and Purdue Extension (2015).
10. Mulching the Landscape, EC1274 (2014; latest edition), Anne M. Streich, Zac J. Reicher and Kim A. Todd, University of Nebraska–Lincoln Extension. Checked Oct 24, 2026.
11. Jury still out on use of rubber mulch (Dec 4, 2015), Rosie Lerner, Purdue Consumer Horticulture. Checked Oct 23, 2026.
12. Miracle-Gro Multi-Colored Hardwood Mulch, 1.5 cu ft, Ace Hardware. Checked Oct 23, 2026.
13. Viagrow 1.5 cu ft Rubber Playground and Landscape Mulch, Home Depot. Checked Oct 22, 2026.
14. Grade A All Bark Cedar Mulch, 3 cu ft, Johnson's Garden. Checked Oct 22, 2026.
15. Proper Mulching Techniques (Tree Care Basics), modified March 2024, Sarah Vogel and Jenny Lee, University of Illinois Extension. Checked Oct 23, 2026.
16. Outdoor Home Playground Safety Handbook, Pub. 324 (2005), U.S. Consumer Product Safety Commission. Checked Oct 23, 2026.
17. Installed depth for home equipment under 4 ft, derived from CPSC Pub. 324. Checked Oct 23, 2026. CPSC Pub. 324 gives 6 in to keep under 4 ft but no installed depth. ScapeCalc applies the handbook’s 12-to-9 in settling (25%): 6 ÷ 0.75 = 8 in installed. An interpretation, not CPSC guidance.
18. ScapeCalc default (no published standard; editable). Checked Oct 22, 2026.
19. Public Playground Safety Handbook, Pub. 325 (July 2025 edition), U.S. Consumer Product Safety Commission (PDF). Checked Oct 23, 2026.
20. ASTM F1292, Standard Specification for Impact Attenuation of Surfacing Materials Within the Use Zone of Playground Equipment (current edition F1292-26), ASTM International. Checked Oct 23, 2026. ASTM lists F1292-26 as active (updated Sep 14, 2026); F1292-22 is historical. Named as CPSC cites it; ScapeCalc has not reviewed the standard.
21. ASTM F2075, Standard Specification for Engineered Wood Fiber for Use as a Playground Safety Surface (current edition F2075-26), ASTM International. Checked Oct 23, 2026. ASTM lists F2075-26 as active (updated Jul 16, 2026); F2075-20 is historical. Named as CPSC cites it; ScapeCalc has not reviewed the standard.
22. ASTM F3012, Standard Specification for Loose-Fill Rubber for Use as a Playground Safety Surface (current edition F3012-22), ASTM International. Checked Oct 23, 2026. ASTM lists F3012-22 as active (updated Feb 14, 2022). Named as CPSC cites it; ScapeCalc has not reviewed the standard.
23. Mounds upon Mounds of Mulch (undated), Purdue Landscape Working Group, Purdue University. Checked Oct 23, 2026.
24. Mulch Volcanoes Kill Trees (May 24, 2024), Annette Cormany, University of Maryland Extension. Checked Oct 23, 2026.
25. Tree-care post defining the 3-3-3 mulching rule (first published 2011), Casey Trees. Checked Oct 24, 2026.

Corrections policy

Found an error? Email contact@scapecalc.com. Each report is checked against the source. Confirmed errors are fixed, and the fix is recorded in the change log below with its date.

Change log