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Mulch Bed Calculator · Free calculator

20x20 Mulch Bed Calculator

Mulching a 20' × 20' bed (400 sq ft) 3" deep takes 3.89 cubic yards — 53 bags of 2 cu ft mulch with 5% extra. Here's 2", 3" and 4" depth, bag vs bulk cost and the fabric and edging for 20x20.

Quick answer

3" deep (standard)
3.89 yd³
2 cu ft bags @ 3"
53
2 cu ft bags @ 2"
35
Bags cost @ 3"
$212
Bulk cost @ 3"
$160
Edging
80 LF

▍Mulch Calculator

Material
ft
in
ft
in
in
Waste Factor
$
L = 20' 0"W = 20' 0"D = 3"
Cubic Yards
3.89yd³
incl. 5% waste · Bulk delivery: order 4.00 yd³
Cubic Feet
105.00ft³
Area
400.0sq ft
Weight
1.17tons
Weight
2,333lbs
Mulch bags needed
  • 2 cu ft bag (2 ft³ yield)53

Mulch for a 20x20 bed by depth

400 sq ft, 5% extra. Bags ~$4.00 (2 cu ft), bulk ~$40/yd³.

DepthUseCubic yards2 cu ft bagsBags $Bulk $Weight
2"Refresh existing bed2.59 yd³35$140$1101,556 lbs
3"Standard (weed control)3.89 yd³53$212$1602,333 lbs
4"New bed / heavy weeds5.19 yd³70$280$2103,111 lbs

Bed prep for 20x20

ItemQuantityNotes
Landscape fabric (3' × 50' rolls)3440 sq ft incl. 10% overlap
Bed edging (20' sections)480 LF perimeter
Fabric staples45~1 per 9 sq ft
Pickup loads (≈2.5 yd³)2bulk mulch @ 3"

How the math works

  1. Area: 20 ft × 20 ft = 400 sq ft
  2. Volume @ 3": 400 × (3 ÷ 12) = 100.00 cu ft
  3. Add 5%: 100.00 × 1.05 = 105.00 cu ft
  4. Cubic yards: 105.00 ÷ 27 = 3.89 yd³
  5. Bags: 105.00 ÷ 2 cu ft = 53 bags

Trade pro tips

  • 3.89 yd³ at 3" — bulk delivery will be cheaper than bags.
  • Keep mulch 2"–3" away from trunks and siding — no "mulch volcanoes".
  • Refreshing an existing bed usually only needs 1"–2" on top.
  • One cubic yard of bulk mulch = 13.5 two-cu-ft bags.
  • A half-ton pickup carries 2–3 yd³ of mulch; a full-size bed with sides can take about 3.

Frequently asked questions

How many bags of mulch do I need for a 20x20 area?

At 3" deep, 53 bags of 2 cu ft mulch. At 2": 35 bags. At 4": 70 bags. All include 5% extra for 400 sq ft.

How many yards of mulch for 20x20?

2": 2.59 yd³; 3": 3.89 yd³; 4": 5.19 yd³. Bulk mulch is sold by the cubic yard; 1 yd³ = 13.5 bags of 2 cu ft.

How much does it cost to mulch a 20x20 bed?

At 3": about $212 in bags or $160 in bulk before delivery. Bulk is usually cheaper at this size.

How much does the mulch for 20x20 weigh?

About 2,333 lbs at 3" (mulch runs 400–800 lbs per yd³ depending on moisture). That's 1.6 half-ton pickup loads of bulk mulch.