DIYCalcLab

Topic · Landscaping estimating

Loose materials: depth, volume, bags and tonnes

By DIYCalcLab Editorial Team · Updated

This page is the method, not the tool list. Loose landscaping materials start as area times depth. Mulch is then bags or cubic yards. Gravel is then a weight, using a density. Recommended depths stay on the landscaping guide. Each material keeps its own calculator.

  • Free
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  • Transparent calculations
  • US & metric

Open Mulch calculator →All landscaping calculators

Start here

Core calculators

Start with the tool that matches your job. Each page shows the formula, defaults, shopping list and sources.

Volume formulas

  • Volume = area × depth
  • Mulch bags = volume ÷ bag volume, rounded up. US defaults are 2 or 3 cu ft; metric defaults are 50 or 70 L
  • Gravel weight (t) = volume (m³) × density (t/m³). Short tons = tonnes × 1,000 ÷ 907.18
  • The gravel calculator’s default waste is 5%. The mulch calculator’s settling field defaults to 0%

Variables

Mulch depth
Calculator default is 3 in or 7.5 cm. Iowa State University Extension describes many hardwood mulches spread between 2 and 4 inches
Gravel density
Crushed-stone default on this site is 1.6 t/m³. Pea 1.52, river rock 1.45, decomposed granite 1.6. Sub-base / MOT Type 1 default is 2.1 and is a site assumption
Supplier density
Replaces the default. Holcim’s UK table lists gravel aggregate at 1.6 t/m³ and Type 1 sub-base at 1.6–1.7, which is not this site’s 2.1
Factors already used by the mulch and gravel calculators
FromTo
1 cu yd27 cu ft
1 cu yd0.7645549 m³ (NIST)
1 short ton907.1847 kg (NIST), so tonnes × 1,000 ÷ 907.18 ≈ short tons
Mulch bags2 cu ft, 3 cu ft, 50 L, 70 L — not an 80 lb concrete bag

Worked examples

Each example uses the same inputs as the linked calculator. The link loads those inputs; the page URL without parameters stays the canonical.

20 × 5 ft mulch bed, 3 in deep, 2 cu ft bags, no settling extra

Imperial · length 20 ft · width 5 ft · depth 3 in · bag 2 cu ft · settling 0%

  1. Area = 100 sq ft
  2. Volume = 100 × 3 ÷ 12 = 25 cu ft = 0.93 cu yd
  3. Bags = 25 ÷ 2 = 12.5 → 13 × 2 cu ft bags

Result: 0.93 cu yd (25 cu ft). Purchase: 13 × 2 cu ft bags.

Open this example in the calculator →

6 × 1.5 m mulch bed, 7.5 cm deep, 50 L bags, no settling extra

Metric · length 6 m · width 1.5 m · depth 7.5 cm · bag 50 L · settling 0%

  1. Area = 9 m²
  2. Volume = 9 × 0.075 = 0.67 m³ = 675 L
  3. Bags = 675 ÷ 50 = 13.5 → 14 × 50 L bags

Result: 0.67 m³ (675 L). Purchase: 14 × 50 L bags.

Open this example in the calculator →

20 × 10 ft crushed-stone path, 3 in deep, 5% waste

Imperial · length 20 ft · width 10 ft · depth 3 in · material crushed stone · density default 1.6 t/m³ · waste 5%

  1. Area = 200 sq ft
  2. Volume with 5% = 1.94 cu yd (52 cu ft)
  3. Weight at 1.6 t/m³ = 2.38 t = 2.62 short tons

Result: 2.62 tons (2.38 t, 1.94 cu yd) at 1.6 t/m³ with 5% waste.

Open this example in the calculator →

Settling and compaction are per material

  • Mulch: the settling field defaults to 0. The field help says fresh mulch can take 5–10% extra if you want the same depth after it settles. The worked example leaves that field at 0.
  • Gravel: the calculator defaults to 5% and its help text says 5–10% for compaction and an uneven sub-grade. The worked example uses that 5% default. Decorative pea gravel is called out in the depth guide as needing little compaction; change the percent on the calculator when that is the case.
  • Topsoil settling, paver base and retaining-wall drainage stone stay on their own calculators, with their own percents.

Limits

  • Retaining walls over about 4 ft have structural and permit consequences. This page only links the block calculator; it does not size the wall.
  • The 2.1 t/m³ sub-base default is not the Holcim Type 1 figure cited above. Enter the supplier density before ordering base stone.
  • Cubic-yard conversions can be checked on the cubic yard calculator. That calculator’s topic link remains the concrete topic, because the id is already listed there.
  • Bag counts use 2 cu ft, 3 cu ft, 50 L or 70 L. A 2 cu ft mulch bag is a retail size (Scotts lists 2 cu ft); it is not a universal bag.

Related calculators

Guides

Quick questions

Why does mulch default to 0% extra and gravel to 5%?

They are separate fields. The mulch settling field defaults to 0; its help text says fresh mulch can take 5–10% extra if you want the same depth after it settles. The gravel calculator defaults to 5%, and its help text says 5–10% for compaction and an uneven sub-grade. Decorative pea gravel is called out in the depth guide as needing little compaction, so change the percent on that job. These percents are not copied from the concrete waste table.

Is the 2.1 t/m³ sub-base figure a Holcim density?

No. The crushed-stone default on this site is 1.6 t/m³, with pea 1.52, river rock 1.45 and decomposed granite 1.6. The sub-base / MOT Type 1 default of 2.1 t/m³ is a site assumption. Holcim’s UK table lists gravel aggregate at 1.6 t/m³ and Type 1 sub-base at 1.6–1.7. Enter the supplier density before ordering base stone.

Are mulch bags the same as concrete bags?

No. Mulch bags on these calculators are 2 cu ft, 3 cu ft, 50 L or 70 L. A 2 cu ft bag is a retail size Scotts lists; it is not a universal bag, and it is not an 80 lb concrete bag. Depth tables stay on the landscaping guide. This page is the volume method. The landscaping category hub is the tool list. Walls over about 4 ft are only linked from here; this page does not size them.

Sources

  1. Iowa State University Extension – How to determine the amount of mulch needed for a garden bed — accessed : “Many hardwood chipped or shredded mulches are spread between 2 and 4 inches thick.”
  2. Scotts – Nature Scapes Color Enhanced Mulch — accessed : “Nature Scapes Color Enhanced Mulch 2 cu. ft. … Size: 2 CF / 1.5 CF”
  3. Holcim UK – Aggregate & sub-base calculator (density table, t/m³) — accessed : “Gravel Aggregate 1.6 · Single Sized Aggregate (Limestone) 1.6 / (Hardstone) 1.55 · Type 1 Subbase (Limestone) 1.7 / (Hardstone) 1.6”
  4. NIST SP 811, Appendix B.9 – conversion factors — accessed : “ton, short (2000 lb) → kilogram (kg): 9.071 847 E+02; cubic yard (yd³) → cubic meter (m³): 7.645 549 E−01”

Prefer manufacturer data sheets and published factors. Coverage, yield and waste vary by product — confirm the label you buy.

Looking for every landscaping tool in one list? See the Landscaping calculators category hub · Methodology · Updated